All,
Finally found a used Tormek at a great price and started sharpening some knives. The first results were rough, but I've come around pretty well over the past few days. I now have some knives that are definitely sharp enough to catch my thumbnail, but don't quite push-cut paper or shave my arm hair. I'm thinking maybe it's a burr issue? Additionally, these are fairly cheap knives so I don't know what kind of edge to expect. That leads me to two basic questions, which I've seen somewhat answered elsewhere on the forum but can't seem to find now that I need help.
1) When I'm grading the stone, I've been told you should put quite a bit of pressure on it for a good deal of time. I have gotten a pretty glassy finish when aiming for 1000 grit, so that seems okay. The issue is that when I press down, it's not uncommon for the wheel to slow or even stop and the holding nut to loosen. I take it this is not what is supposed to occur. Maybe some maintenance is in order?
2) I've yet to figure out how much time should be spent on each step of the process. I have been told you should always use 220 first, even if it's just really quick, but also heard that you don't really need to do that unless your edge is really lousy or nicked. Then, I've heard that you need to really spend time on the 1000 grit (after spending a lot of time grading it), but others say that stropping on the leather wheel is often overlooked. I know it's not a formula, but should I be spending the majority of the time on one or the other?
Thanks in advance--fun forum! I have the planer/jointer jig and will eventually tackle those once I do some more knives and some handplanes/chisels.
Cheers,
Ben
1. Sometimes the drive wheel will harden slightly, and people recommend hitting it with light sandpaper to cause it not to stick.
http://forum.tormek.com/index.php?topic=241.msg702#msg702
2. I have taken restaurant grade (NSF approved) inexpensive starter chef's knives ($6 to $50), from no edge to paper cutting edge with just the 1000 grit and polishing. Cheap knives probably won't last as well as good knives, but price doesn't always equate to quality. I have yet to use 220 on one, but also haven't dealt with a chipped one yet. You could cut well off the stone, but I think you really need the honing step to cut paper.
Welcome to the form, Ben. The first thing you should do is register your Tormek. You can find the registration button on tormek.com , the same website as this forum. Whether or not you get any warranty by registering, you can download the latest edition of the handbook. The basic handbook has not changed, so it will help you with whatever model you have.
Do an online search for tormek videos. Pay particular attention to the videos by Jeff Farris. They are an excellent path to get you up and running. Stumpy Nubs' interview with Stig is an outstanding introduction to the Tormek.
Light sanding of the rubber drive wheel is the standard approved method of preventing slippage.
The handbook describes how to tap the grinding wheel a bit tighter. Once you download the handbook, fill an insulated mug with coffee and carefully read through it. If you happen to have a printed copy, use it as a working reference.
Start out by using the stone grader more than you think you need to. You can feel the difference in the wheel with your fingers. You can also hear the difference.
Don't hesitate to post questions; that's why we are here.
Ken
"...but don't quite push-cut paper or shave my arm hair. I'm thinking maybe it's a burr issue?"
It's amazing how any remaining burr can make a blade seem dull. Generally you can feel a burr by pulling your fingertip away from the edge. Same thing by very gently pulling your fingernail over the blade and away from the edge.
Use a loupe and examine the edge under a good light. If there is a burr, you will probably be able to see it.
Drag a cotton ball or some gauze along the edge. A burr will catch the material.
Very, very, VERY gently drag the tip of your fingernail along the length of the blade. You will be able to feel any imperfections.
Get a piece of soft wood like pine and gently drag the blade over (like you are cutting into it) the edge of a cut end. This will tear off or bend down any burr that might be sticking straight out from the blade. Then hone the blade again. If the blade suddenly gets sharp then you know that your honing process is not completely removing burr. It's an interesting experiment to try if you think that there is a burr issue.
"I have been told you should always use 220 first..."
220 grit is very aggressive, may well not be necessary, and removes a lot of steel quickly. It could remove more metal than you need to. It really just depends on how hard the steel is and how dull the blade is to start with. This can vary from blade to blade. This will take a little experience, but you will get the hang of it before you know it.
Here's some really good advice:
Second hand stores like Salvation Army, etc., often have lots of crap (and sometimes good) knives for really cheap. Like $0.25 - $0.50 per knife. Buy some and have at it. See how the different types of steel are more or less hard to sharpen. Grind the edge off a knife and then sharpen it. Use 220 grit and 1000 grit. Try in between grits by just not using the stone grader for so long. Press hard at 220 grit and watch what happens. Press gently a 220 grit and see what happens. Do the same at 1000 grit. Start with 1000 grit and see how long it takes to grind the scallops off part of a junker serrated knife. Then switch to 220 grit and see the difference on another section of the blade. Stuff like that.
After about 5 knives, you will pretty much have a grip on it. It really does not take that long to catch on to what's going on. You don't need to overthink this just because it's a Tormek. When you consider it, in many ways it's just a super slow bench grinder with different grit wheels.
Just think of it like sandpaper on wood. You would not use 80 grit sandpaper between applications of poly on a table top for example. Similarly, you don't need 220 grit to touch up a mostly sharp blade or a blade with softer steel, etc.
If you are not sure, start with a finer grit and then move to a rougher wheel if you need to because it's taking forever, or if you want to remove a bunch of metal quickly. A 220 grit wheel can turn a pocket knife blade into a toothpick in no time!
Personally, I have yet to find a way to put steel back on a blade.
Hope that helps. :)
Good thoughts, Grepper (as always).
We should never think of removing the burr as an after thought. It is an important part of the sharpening operation.
What good is the fine technology of jigs for repeatable sharpening with minimal steel removal if a coarse stone reduces the tool to a toothpick?
Jeff Farris mentioned that most knife sharpening is best done without using the coarse grading of the SG-250. (In his knife sharpening youtube) I am convinced the same logic would apply with other tools, such as carving tools. However, the handbook is strangely silent on this issue. I would like to see this covered in some depth in a Tormek video.
Ken
Quote from: Ken S on October 15, 2016, 09:43:24 PM
However, the handbook is strangely silent on this issue. I would like to see this covered in some depth in a Tormek video.
Ken
Personally, I expect this not to be an oversite, but a thought that what a butcher might do, is different from a chef, or someone who cooks at home, to someone who just abuses knifes. Varies too much and better to learn from experience.
I would lean toward an oversite. Torgny Jansson wrote a comprehensive handbook. I believe the scope of the Tormek expanded more rapidly than the rewrite time.
I'm not interested in throwing stones. I would just like to see the handbook include some things which were not included in the original. Yes, we all learn from experience. I like to give experience a good start.
Ken
Excellent advice from everyone. I have a few knives sitting around that I don't care too much about and will be testing the tool on. I think I've come to see that the 220 grit is a bit much and that I can do better with the 1000, generally. I plan on doing some maintenance later today to hopefully prevent slippage. I'll keep looking for videos too.
I still am struggling to know how many honing passes I need on the stropping wheel. A few of the videos I've found seem to show them just doing a few quick strokes on each side. Other posts I read on here suggest that people neglect this step too frequently, only doing a couple passes when they should be spending more time. I'll keep experimenting, but would love to know what folks here generally do for knives.
I have registered (thanks for that!) and have the handbook. Actually, I have a printed copy from the guy I bought the Tormek from, it's nice, but there are some updates in the digital copy I'm reading, I think. One area where I'm becoming confused is proper use of the angle setter. Trying to measure my own blades' angles has me confused. The picture implies that for some, you can set it directly to the angle, but for others you should be setting it at half, and it has to with blade thickness? I have just been sharpening at 20 degrees on each side, hopefully that's okay.
Thanks again for your thoughts and any more to follow,
Ben
Quote from: mannofiron on October 16, 2016, 05:54:02 PM
I still am struggling to know how many honing passes I need on the stropping wheel.
Ben, I hone the edge slowly applying quite big pressure. After some three or four passes on each side I test the edge sharpness using the paper test. When the paper is cut cleanly by just pressing the knife down I stop the intensive honing and add several light passes to improve the finish of the edge.
Quote from: mannofiron on October 16, 2016, 05:54:02 PM
One area where I'm becoming confused is proper use of the angle setter. Trying to measure my own blades' angles has me confused. The picture implies that for some, you can set it directly to the angle, but for others you should be setting it at half, and it has to with blade thickness? I have just been sharpening at 20 degrees on each side, hopefully that's okay.
Correct use of the AngleMaster is challenging not only for you. :) You can easily check if your angle setup was correct by measuring the sharpened edge angle using the grooves of the AngleMaster.
Later you can test the kenjig concept or the Wootz approach, which are immune to blade tapering issues and provide quick and very accurate angle setup. ;)
Be careful when sharpening very thin or very thick knives. The knife jig works flawlessly for blade thicknesses between 2 and 3 mm. ;)
Jan
Don't forget the black marker. It is a must have and use tool.
Ken
Quote from: grepper on October 15, 2016, 05:01:36 AM
It's amazing how any remaining burr can make a blade seem dull. Generally you can feel a burr by pulling your fingertip away from the edge. Same thing by very gently pulling your fingernail over the blade and away from the edge.
I like to drag the blade across an old cloth towel, in the direction opposite to the direction you'd move the knife to cut something. Then examine the edge under a magnifying glass with good light. Threads snagged off the towel will be visible if there's a burr.
I agree that getting rid of the burr is essential if you want to shave hair or slice paper.
Quote from: mannofiron on October 16, 2016, 05:54:02 PM
One area where I'm becoming confused is proper use of the angle setter. Trying to measure my own blades' angles has me confused. The picture implies that for some, you can set it directly to the angle, but for others you should be setting it at half, and it has to with blade thickness? I have just been sharpening at 20 degrees on each side, hopefully that's okay.
Thanks again for your thoughts and any more to follow,
Ben
The angle setter is for multiple tools. Most of the kitchen knives in the USA and Europe, are western style, two sided. Eastern style (namely Japanese) may have the blade only on one side. Chinese style I have been told, tends to use more a cleaver (giant knife for all). I don't remember what my Korean neighbors did when I was a kid, I got out of there when I smelled something horrible (spelling, Kim Chee?).
So two sided knives, divide in half. Single sided, don't. Then you have Chisels and plane blades, which are one sided and don't get divided.
Blade thickness, is more about trying to get a uniform bevel. The first time you do one and see the bevel more on one side then the other, you will get that.
Buffing for me depends on the knife. I spend more time buffing a serrated edge knife, then I do a Chef's knife that isn't completely edge less. (wore down to nothing but a lettuce knife) The towel trick is good as well as the fingernail trick, and the pen test, trick.
https://www.youtube.com/watch?v=rzWdpjyDZKM
Now, IMHO, part of the stropping discrepancy, is how often do you sharpen your knives? If often, then it will not take as much to get back to sharp (less burr), if infrequent, I expect you would get a bigger burr, and need to hone longer.
Quote from: Herman Trivilino on October 16, 2016, 11:21:49 PM
I agree that getting rid of the burr is essential if you want to shave hair or slice paper.
Herman is correct. Burr removal is absolutely necessary.
From personal experience, you can grind away and a blade just won't get sharp even though from the sharpening process it just has to be. But for some reason, it is not. Then... remove the burr and suddenly, almost magically, it's hair splitting sharp!
Why is this? Because a burr is a pile of metal on the edge of the blade. If you don't get rid of it, the burr material will get smashed down over the edge and "hide" the sharp edge under the burr.
Burrs vary in both amount metal forming the burr and type of burr. Some are true "wire edge" burrs many times thicker than the edge. Others are sparse or stick directly out from the edge.
When an edge is honed on leather, the burr material is bent from side to side until it fractures from metal fatigue and breaks off, or catches on the leather directly and is torn from the edge revealing the sharp edge under the burr material.
Viewing a burr, it's pretty easy to imagine what happens if you drag a burred edge gently across the edge of soft wood. Much of the burr gets torn off, and the rest gets smushed (technical term) down and bent over the edge making it easily removed by honing because it is more easily caught up in the leather honing wheel than if the burr is extending straight out from the edge.
As Herman suggests, you can detect a burr because it will catch on cotton or gauze material if you drag a blade across it, or just use a good loupe and a good light or microscope to examine the blade.
If you don't completely remove the burr one of two things will happen:
1. The burr material will get bent over the edge and the blade will never get sharp.
2. If you are lucky ??? :), the blade will magically get sharper as you use it because the burr material will be torn off and lodge itself in you evening's broccoli.
Here are some images that I have taken of various burrs that are useful in understanding what's happening:
(http://i1275.photobucket.com/albums/y441/grepper00/Burr4_zpsbxl7yhwp.jpg)
(http://i1275.photobucket.com/albums/y441/grepper00/Burr3_zpsyzwhvvkn.jpg)
(http://i1275.photobucket.com/albums/y441/grepper00/Burr2_zpsb2ohyrbn.jpg)
(http://i1275.photobucket.com/albums/y441/grepper00/burr1_zpscrqrptlb.jpg)
Really nice description and photos, Grepper, appreciated! :)
Jan
This topic illustrates the need for both knowledge of the Tormek and sharpening theory. The sharpening theory is so important that Steve Bottorff devoted a whole chapter to it in his Sharpening School DVD. I do not mean to be an infomercial for Steve, however, I know of no other video source as informative.
I will also add another recommendation for my favorite reference book by Leonard Lee.
Good sharpening is a combination of technical skill and knowledge.
Ken
Quote from: mannofiron on October 16, 2016, 05:54:02 PM
I still am struggling to know how many honing passes I need on the stropping wheel.
So, how many passes on the honing wheel is required? Exactly three. Or ten. Or seven. That is a difficult question to answer because the real answer is that you need to hone until the burr is removed and/or you have achieved the desired polishing of the bevel you wish.
The amount of metal in and the type of burr formed depends mostly on two factors; the coarseness of the grindstone and the hardness of the steel. A coarse grind will tear at the cutting edge producing a thicker, chunkier burr. A smooth grindstone removes less metal more evenly and produces a thinner, more even burr. Of course the angle of grinding will also play a part.
Harder steel tends to be more brittle and chip easily. When sharpening, it tends to produce smaller, irregular burrs because the brittle steel simply breaks off rather then bending over the edge.
Softer steel, being more malleable, tends to produce more burr because it simply bends at the edge and stays intact. Observe the image at the end of this post. Here the burr has actually formed a roll of steel bent away from the edge. It is a classic "wire edge" burr. Shaving would be very uncomfortable with that blade!
Oddly, hard and soft steel is somewhat similar to a bar of chocolate. If you take a potato peeler to the edge of a hard, cold bar of chocolate, the chocolate just crumbles into pieces.
(http://i1275.photobucket.com/albums/y441/grepper00/Burr7%20chips_zpshtm58sqd.jpg)
But let the chocolate warm and soften some and it forms decorative chocolate curls you can use to embellish tasty culinary delights.
(http://i1275.photobucket.com/albums/y441/grepper00/Burr8%20curls_zpsf80y6eob.jpg)
So, how much honing is required? Well, consider the below image of a burr. If you press the side of the blade opposite the roll burr against the honing wheel probably not much will happen because the burr will not impact the wheel. But flip the blade over and the bulging burr will be bent in the opposite direction over the cutting edge. After a few iterations the metal will fatigue and the burr will start to break away. However because the steel is softer and more malleable, it may take a more bending back and forth than would a harder more brittle steel.
But... check out some of the images in the previous post where the burr sticks straight out from the edge and imagine what happens when those blades are pressed against the honing wheel. Because the burr extends straight off the edge, very little bending occurs because the burr only slightly impacts the leather. However, the leather is soft compared to the blade and depresses slightly when the blade is pressed against it causing some wrapping of the leather around the cutting edge.
That is why it can be useful to wipe the blade over a piece of towel or soft wood to tear away and/or deform the burr to increase contact with the honing wheel. If you have a blade that is not getting sharp even after some honing and you suspect a burr is the issue, try it. It actually works! The results can be surprising and dramatic.
Hopefully that helps in answering your question as to how many passes on the honing wheel are required. Exactly three. Or ten. Or seven. :)
(http://i1275.photobucket.com/albums/y441/grepper00/Burr6_zps8u2mwkh1.jpg)
Another very nice and well documented burr removal consideration, Grepper, thanks. Much appreciated! :)
Jan
Thanks, Jan. Any time! Its cool how once you get a good look at a burr and give it a little thought, it all becomes clear what's happening. But then, I guess that's true of a lot of things. :)
Wise words, I fully agree with you! :)
Jan
Mark, that second image reminds me of a saw blade! That knife will slice tomatoes nicely.
Slicing through paper and shaving arm hair are nice parts of a demonstration designed to impress potential customers, but they don't necessarily tell you how well a knife will perform. A very sharp knife that will shave arm hair might last only a few sessions in the kitchen as the edge may easily break off. How long an edge lasts is sometimes more important than its first performance.
Quote from: grepper on October 17, 2016, 06:53:33 PM
That is why it can be useful to wipe the blade over a piece of towel or soft wood to tear away and/or deform the burr to increase contact with the honing wheel.
Ahhh... So my technique of wiping the blade to check for burrs may actually aid in the removal of the burr. Good to know. :)
Quote from: Herman Trivilino on October 18, 2016, 03:39:10 AM
Slicing through paper and shaving arm hair are nice parts of a demonstration designed to impress potential customers, but they don't necessarily tell you how well a knife will perform. A very sharp knife that will shave arm hair might last only a few sessions in the kitchen as the edge may easily break off. How long an edge lasts is sometimes more important than its first performance.
Herman,
I gotta agree with that! For general kitchen use, a highly polished super smooth edge that works well for shaving and push cutting paper just won't last very long at all. It's not that difficult to produce a polished, perfectly smooth edge that you can shave with and will slice tomato, broccoli and onion skin and not ride on the surface, but it has to be really super sharp and an edge that sharp and thin just doesn't hold up at all. A few contacts with the cutting board and almost immediately there is a noticeable decrease in sharpness and it starts riding on tomato skin. From personal experience, it does a great job of slicing through human skin though! It slices finger meat so cleanly the first thing you notice is epidermal leakage, and it doesn't hurt until the source of the leakage is discovered and observed.
Of course there is a big difference between a more saw like edge created by sharpening with a coarse grit and a rough edge caused by piles of burr smushed down on the edge. The former is sharp like a saw, while the latter is just plain rough like a wire covered with abrasive compound that abrades it way through stuff.
Quote from: Herman Trivilino on October 18, 2016, 03:44:49 AM
Ahhh... So my technique of wiping the blade to check for burrs may actually aid in the removal of the burr. Good to know. :)
I know you have a 40X microscope and I would be interested in your observations. Get a good burr going and carefully examine it under the scope. Then give it a few good wipes on the old towel and examine the burr again. What do you see? Then drag the blade down the edge (with the grain) of a piece of pine board and examine the burr under the scope again. How does that compare with the old towel wipe?
Here is a progression of sharpening and honing from a very coarse grind burr covered mess to a polished, super sharp most excellent finger meat slicer. The first one, after burr removal, would be an excellent tomato skin slicer!
Kind of interesting to see how it progresses. As the blade is sharpened with finer and finer abrasives, the grooving on the bevel is smoothed away, ending with the final, highly polished with Tormek compound, finger meat slicing, mirror bevel finish.
The blue marker on the bevel was so that I could photograph the same area of the blade.
(http://i1275.photobucket.com/albums/y441/grepper00/progession2_zps1igf5qb1.jpg)
Grepper, inspired by your nice microscopic images of knife edges I began to look at home for some microscope. I have found an ancient pocket microscope shown below. Do you think it may be good for burr observation? I have to clean the lenses and add some LED illumination, an opening for it is there ready. ;)
On the housing there is a figure 278. I am wondering if it describes the magnification or the serial number. ???
Jan
That's an antique all right!
I have no idea about those numbers either and I'm no expert on microscopes. While it does look like there is enough room for 278X worth of lenses, 278X would be an odd magnification level. You know, generally you see stuff like 40X, 100X, 150X, etc.
I did a quick search and found nothing other than a bunch of antique scopes on Ebay. If you dissemble it, there might be some markings on the lens rings that would enable you to figure it out, but who knows. It might have a very small field maybe only a few planeria wide, but really I'm just babbling.
Have at it! Just stick a ruler under it and, dirty lenses and all, and see what you see!!! That should quickly tell you if it's worth pursuing.
Any amount of magnification is better than none. Herman has a 40X scope. He may have some comments on how good that is for checking out blades.
http://www.freshairphotography.co.uk/services/photomicrography/#prettyPhoto[gallery]/0/
I'm using a 200X, 5 mp USB scope. It don't think the images I posted are 200X but somewhere between 50x and 200X. With the cheap USB scopes, the mag level changes when the lens to subject distance varies and they can focus at different distances, so there is no way to really know the mag level.
You can pick up a USB scope for $25-$35 to play with. Some go to 800X, but really 200X is about the max for checking out blades. Any more mag than that and the depth of field becomes so shallow that the top side of a pin is in focus but the bottom is not. Very difficult to work with.
The cheap USB scopes are futsy to use. Difficult to focus because the slightest bump throws them out of focus and you have to touch them to focus. Move the blade and it's out of focus again. Lighting reflective surfaces is problematic too.
The biggest problem is holding the scope and blade perfectly still. I even thought of mounting the scope on my milling machine to use as a rock solid adjustable stand, but the mill and computer are in different rooms.
Nonetheless it's a lot of fun to play with and pretty interesting!
Let us know what you see with you new toy!
Grepper, thanks for your thoughts and recommendations. :) You are correct, it is rather a toy than a tool for checking blades. The aperture is very small. The figure 278 is probably a serial number and not magnification. The major disadvantage is that the microscopic images cannot be stored and shared. ;)
Jan
If you want to store and share your images then you have two options. USB scopes, $20 to a $A LOT, or camera attachments for regular optical scopes, $A LOT to $A WHOLE LOT More.
My advice would be to get a $20 - $50 USB scope just to check it out and have some fun. As you can see they actually work and are useful. Right off you will see what I mean about the focusing issue. It's totally doable, just futsy. Purchasing or making a rock solid, adjustable stand would go a long way. I've just cursed the issue every time I use the thing, but put up with it nonetheless.
The more optical megapixels the better. Ignore interpolated or digital magnification- you can just use Photoshop to zoom later-same thing. Get at LEAST a 2mp model - 5mp is better. Get USB 3.0 if you can, but last I looked those were few and far between and you pay a super premium. USB 2.0 is so slow that when you move the subject there is a huge and jerky delay on the computer screen. That pretty much rules it out as a live field tool (something I really wanted) for doing micro-soldering for example, let alone doing anything like injecting cells with DNA strands to GM a tomato cultivar to have soft skin so you don't need such sharp knives to cut it.
Get one! They are inexpensive, informative and fun. Then post some pics and show why some knife you have just won't get sharp and how if you had gotten a USB scope sooner you would not have ground the knife down to a toothpick trying to get it sharp because you would have understood what was happening down there on the edge!
Thanks again for your valuable advice. :)
Jan
Quote from: grepper on October 18, 2016, 05:06:23 AM
Kind of interesting to see how it progresses. As the blade is sharpened with finer and finer abrasives, the grooving on the bevel is smoothed away, ending with the final, highly polished with Tormek compound, finger meat slicing, mirror bevel finish.
What were the abrasives used in the progression? I'm no expert but my experience with sanding wood indicates to me that somewhere along the way, likely in the step immediately after using the Tormek grindstone prepared in the fine state, there was too large of a step in abrasives or grit size. The reason I say this is in the final image you can see that the deepest grooves left behind by a more abrasive grit were not removed by later less abrasive grits. The spaces between the grooves are polished to a mirror finish, indicating that the finest of grits did their job well.
I have seen the same thing after applying a finish to a piece of wood. Sand, for example, with 80 grit sand paper followed immediately by 220 grit and you'll see a smooth surface in between deep groves left behind by the 80 grit abrasive. You will need to apply a finish to see this, even if it's only some mineral spirits applied with a rag.
That's a nice looking scope, Jan. My guess is that the narrow field of view might be a disappointment. If you look at a ruler with both eyes, one naked and the other scoped, you can with a little practice see both magnified and unmagnified images of the gradations on the ruler. From this you can estimate the magnification.
My scope is a dissecting microscope. It's binocular with a wide field of view and a 40X magnification. It gives me images much like the ones Mark (grepper) posted so I would estimate that the magnification in those images is somewhere around the range 60X to 100X. You want to be able to see a good-sized section of the entire bevel, and 40X seems about right.
I've seen images of knife edges with higher levels of magnification, made with an electron microscope, and they were used to examine the actual edge itself to determine the effectiveness of different sharpening strategies. But here we are interested instead in the polishing of the bevel and burr removal, so less magnification is more desirable.
Grepper and Herman,
I am exhorting my wife to buy for me a school microscope as a Christmas present which makes my budget less tense. Because my shop is in the basement and my computer two floors above I have decided to buy an off line working microscope with LCD display which can store the images on SD memory card. I have now to be a good boy to ensure that my Christmas wish will be fulfilled. :)
I hope it may be good also for grandchildren. I wondering if it would be good to buy also a basic set of prepared slides for use in biological education. :-\
Jan
Herman,
I did that many years ago and I don't remember the actual grits. If memory serves, I started with the Tormek and ended with a belt grinder.
Looking at it, I think you are correct that it required more intermediate grit to achieve a perfectly smooth bevel. I know you are familiar with how, and have seen it yourself on blades, if you use a coarse grit and then quickly go to a finer grit, what you end up with is polished, smooth areas between grooves created by the coarser abrasive.
So, to get a perfectly smooth bevel you either need to progress from a coarse through finer and finer grits, or spend a very long time trying to removing a lot of metal with the fine grit. A lot quicker to do some intermediate grit grinding.
Jan,
You might also start dropping some hints about an early Christmas! :)
My early Christmas present arrived. :)
I have got an off line working microscope with LCD display which can store the images on SD memory card. Optical magnifications are 50X, 125X and 500X.
Grepper and Herman thanks for your guidance! :)
I am attaching two of my first images. The first is the edge of a new Morakniv. The magnification was 100X, so the length of the shown edge segment's is circa 0.7 mm (0.03").
The other image shows a thin layer of Tormek honing compound at 500X magnification. The size of the grains is circa 3 μm.
Jan
Very cool Jan! Much better images than I am able to get with my cheapo USB scope.
Amazing how scratchy bevels and edges look up close, eh? :)
Exactly what scope did you get?
Thank you Grepper, you're too modest, your nice pictures of the burrs and edges inspired me to buy the microscope. Your guidance helped me significantly! :)
I have bought a School LCD Microscope with 3.5" display and 5 MP CMOS sensor manufactured by Bresser GmbH. (Germany). http://www.bresser.de/en/Microscopes-Magnifiers/BRESSER-LCD-Microscope-8-9cm-3-5.html
Comfortable is that it includes a mechanical desk with vernier. http://www.bresser.de/en/Microscopes-Magnifiers/BRESSER-Biolux-Mechanical-Desk.html
I have bought it via Amazon.de for some 150 EUR (165 USD).
What concerns the Morakniv blade I was also surprised that so many scratches rich to the edge where they weaken the edge and can act as a stress risers. :-\
Jan
Awe shucks, Jan. Twern't noth'n. :)
Quote from: Jan on November 03, 2016, 08:50:52 AM
What concerns the Morakniv blade I was also surprised that so many scratches rich to the edge where they weaken the edge and can act as a stress risers. :-\
Jan
When you get some time to play with your cool new toy, methinks you will find that a perfectly smooth, mirror bevel is an elusive beast indeed! The problem presents well with magnification 100X and greater with good side lighting to show shadows.
Also, the wavelength of light produced by the little LED's on my USB scope shows the grain in steel as different colors that can be mistaken for grooves. Really a pain! So I balance flashlights off to the side to get good side lighting that does not reflect directly back into the scope. Don't know if that kind of problem will manifest its ugly head with your scope or not. Then the sensor in my scope is sensitive to the PWM of my LED flashlights and can make bars in the images. Another pain! I have very few incandescent light sources left in my home, but that would work much better. Anyway, I'm rambling...
Back to the elusive, perfectly smooth bevel: Here is what I think is a 200X image of a blade that I sharpened on a belt sander with at least 5 levels of abrasives starting at, if memory serves correctly, 150 grit thru a 9 micron 3M Microfinishing film belt, then finished on a 3 micron (8000 grit) MicroMesh belt. The MicroMesh belt feels about like grinding with blue jean material or a t-shirt. Then I honed the blade with Tormek Honing Compound using a leather belt and finished with a felt belt and Mother's Mag and Aluminum Polish.
Now... You would think that would tame the elusive beast, eh?. But, noooo! Somewhere in the progression I didn't spend enough time and left some scratches from a coarser grit. For all intents and purposes it looks like a mirror, but with a good little close up look-see, it's still far from perfection. Geeeze! What does it take!
In some future life when I have more time I might try it again, but it is illustrative of what is really happening during sharpening.
The original 5mp BMP image below was 14+MB and more detailed, which was then converted to JPG. If you are looking at the cutting edge, please take into consideration distortion due to resizing and JPG artifacting distorting appearance the smoothness of the edge. That blade was
extremely sharp with a very smooth edge.
I'm looking FW to your images and thoughts on edges, burrs and sharpening!
(http://i1275.photobucket.com/albums/y441/grepper00/bevel_zpsm1jxgmj5.jpg)
Mark (Grepper), I fully agree with you that the "mirror bevel is an elusive beast". :-\
Vanity of vanities, says the Preacher,
vanity of vanities! All is vanity.
What does man gain by all the toil
at which he toils under the sun? (Ecclesiastes 1)
My microscope may be a little bit more advanced than your USB scope but still far from being suitable for metallographic purposes. I do not have a polarisation set.
You are correct, metallurgical microscopes do not have LED illumination but use high intensity halogen light source. I am wondering why the halogen light is better than LED. LED light is coherent and as such may be more prone to interferometric effects which then obscure the observation.
I think we can consider the semi-regular grooves and scratches of a blade as a diffraction gratings causing the rainbow effect in the reflected light. Similar to ordinary pressed CD media.
Jan
I posted an image of the blade with a link pointing to an image in Photobucket. Looks like Photobucket is down for maintenance and the image is not displaying in the forum, so I have attached it to this post.
Jan- I think you defined correctly the cause of how some of the image appear as a rainbow effect due to diffraction. That is exactly how it looks sometimes.
Grepper, thanks for posting the image. If it is really 200X magnification than the edge is perfect. :)
I am wondering what is the dark horizontal "valley" in the middle of the image. :-\
Jan
Yeah, that line looks odd as though there is some valley, but there is really nothing there. I still have the knife and even though it has been sharpened since the image it is still the same. The bevel is a smooth transition from side of the blade.
However, there is a very thin, extremely highly polished area at the top edge of the bevel where it transitions to the side of the blade. That happens because a malleable belt creates a convex bevel as belt flexes around the edge of the blade as it is sharpened and its first point of contact is the top edge of the bevel. Exactly the opposite of the concave grind produced by a grinding wheel.
The extremely fine abrasive belts I used at the end of the process are very soft, flexible, cloth backed belts that very smoothly wrap the bevel. The attached image shows just how soft and flexible they are.
This super polished, highly reflective mirror like area apparently was at such an angle as to not reflect light into the scope and appears to be cavernous, like looking at darkness in a mirror. Like I mentioned, the little USB scope has challenging illumination issues to overcome.
Quote from: Jan on November 04, 2016, 05:41:46 PM
If it is really 200X magnification than the edge is perfect. :)
Jan
I wish I knew exactly what magnification my USB scope is. It is rated @ 200X max optical. It has a dial on the side with a super informative "+" on one side and a "-" on the other. I have it turned all the way to "+".
I recently sharpened a knife and was playing around whittling human hair. Below is an image of the hair I split with the knife and the other image is of the millimeter delineations on a steel ruler.
I don't know what those images really mean. Maybe one of you guys with a microscope with fixed, known magnification levels can make a comparison and form an educated guess as to what magnification I'm really looking at.
Thank you Grepper for your prompt and detailed explanation, appreciated. The absence of a death valley between bevel and side of the blade is for me really interesting. :-\
To estimate the magnification and the hair diameter from your images is not difficult, provided the scope setting was the same for both.* :)
The hair thickness measured on my monitor is circa 5 mm. The distance between the mm marks of the ruler is circa 85 mm. So the hair diameter D = 5 / 85 = 0.06 mm = 60 μm.
The image of the ruler taken by your USB scope was displayed on my monitor with a magnification 85X, because 1 mm of the ruler corresponded to 85 mm on the monitor.
Jan
*P.S.: Also the processing and displaying of the images should be the same, not distorting the length relations. Most accurate is to work with the native scope format.
I'm feeling rather foggy minded at the moment, and I'm having difficulty correlating monitor display with real world measurement.
Not considering the can of worms of comparing two different images, but just when you said:
"The image of the ruler taken by your USB scope was displayed on my monitor with a magnification 85X, because 1 mm of the ruler corresponded to 85 mm on the monitor."
Image files simply contain data representing RGB color values of pixels when displayed on the screen. Wouldn't you need to take into account the PPI of the monitor, the image dimensions, and be sure that the image is being displayed without any scaling (even if aspect ratio was constant during scaling), and only use images that were not scaled to begin with?
It can't be as simple as just holding a ruler up to the screen and measuring the distance of one displayed mm in an image to one mm on a physical ruler.
I'm guessing I'm just having a DUH moment... ::)
It was not my intention to shock you by the simplicity of magnification calculation. Sorry for that. :( The determination of the hair diameter shows that in principle this approach works well. ;)
It is similar to the situation when you have a map with a scale bar. You measure the distance in the map in mm and using the scale you get the distance between objects of the real world.
In our situation the magnification corresponds to the map scale, but is unknown. To determine the magnification we need to know two distances, one is the true size and the other is the size in the image.
Wikipedia says: "Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless number."
Jan
Quote from: grepper on November 04, 2016, 11:39:08 PM
It can't be as simple as just holding a ruler up to the screen and measuring the distance of one displayed mm in an image to one mm on a physical ruler.
It is if, as Jan said, it's the magnification on your monitor. That tells you nothing about the magnification of your scope.
To see this take a photograph of some object with a camera and then carefully scale it so that when you print it the image is the same size as the object. Then post that image on a web site. When others look at that image they will see it with different magnifications. Some will see it reduced in size because they're viewing the web page on their phone. Others will see it enlarged because they're viewing it on a projector screen.
Yes, Herman. That is exactly what I'm trying to say. I don't see how you can infer anything as far as magnification from measuring or comparing images on a particular display device without being able to compare it to a 0.0X magnification image of the same object, or at least a 0.0X magnification of some subject of known dimensions. Obviously an image displayed on a 50" TV is going to be much larger than the same image display on a phone.
Jan- Please ignore my previous post: I reread that sentence in your post and now understand you were just showing an example of something 85x larger than something else and not trying to infer anything as to the magnification of the scope. Doh! Sloppy reading on my part. My apologies.
Obviously, I could take two images with the same device, at the same magnification, and knowing the dimensions of an object in one, determine the size of some object in the other.
If I could take an image with my scope at 0.0X magnification I'd be good to go. Barring that, all I have is a bunch of images at an unknown magnification. Hopefully I'm not missing the forest cuz of all the trees.
Herman – What is your guesstimate as to how those images compare to what you see @ 40X?
I do know the image dimensions, and this display is 1280 pixels horizontally, and the physical display size is ~304 mm horizontally. So, about 4.2 pixels/mm. From that I could approximate the pixel size of this display. I know the approximate field width of the scope on max magnification from the image of the ruler.
Maybe there is something in that from which I could somehow figure the magnification by comparing a displayed image to physical reality. But that that would not be fair! It would require thinking. Nobody ever told me that sharpening would require actual thinking!
Here is a better image for comparison. It is how my scope at full magnification sees the date on a 1968 penny.
Jan- can you post a similar 50X and 100X image? That would be a cool comparison... Crap! I wasn't thinking... You live across the pond from here.
A riddle: What small microscopable object do we have in common?
Quote from: Herman Trivilino on November 05, 2016, 02:58:24 AM
Quote from: grepper on November 04, 2016, 11:39:08 PM
It can't be as simple as just holding a ruler up to the screen and measuring the distance of one displayed mm in an image to one mm on a physical ruler.
It is if, as Jan said, it's the magnification on your monitor. That tells you nothing about the magnification of your scope.
To see this take a photograph of some object with a camera and then carefully scale it so that when you print it the image is the same size as the object. Then post that image on a web site. When others look at that image they will see it with different magnifications. Some will see it reduced in size because they're viewing the web page on their phone. Others will see it enlarged because they're viewing it on a projector screen.
You are correct, Herman. :)
Where the magnification (scale) of an image is important we usually superimpose a scale bar on the picture. The scale bar has a stated length and is resized together with the picture. From a picture with scale bar we can easily calculate the actual magnification regardless image reduction or enlargement. ;)
Jan
Quote from: grepper on November 05, 2016, 04:23:12 AM
Obviously, I could take two images with the same device, at the same magnification, and knowing the dimensions of an object in one, determine the size of some object in the other.
I think you are by leaps and bounds approaching full understanding of the problem. I am very happy about it. :) :)
Jan
P.S.: When you are speaking about 0.0X magnification you have probably in mind 1.0X magnification, because 0.0X means zero apparent size of an object.
Quote from: grepper on November 05, 2016, 05:36:57 AM
Here is a better image for comparison. It is how my scope at full magnification sees the date on a 1968 penny.
Jan- can you post a similar 50X and 100X image? That would be a cool comparison... Crap! I wasn't thinking... You live across the pond from here.
A riddle: What small microscopable object do we have in common?
Mark, attached you can see a hair of my wife, mm marks of a steel ruler and a date on a 1 Euro cent coin, dated 2009 (German edition: Ein Euro Cent).All images were taken with optical magnification 50X and resampled from 3264x2448 to 480x360 pixels.
The calculated hair diameter is circa 70 μm and the calculated height of the figures on the 1 Euro cent is almost 1 mm.
Jan
Jan,
My older eyes have trouble seeing things at 0.0X magnification. Could we try to enlarge things just a bit..... :)
Ken
You overestimate me, Ken. In this country we have a saying: "Where is nothing, not even devil can take." ;)
Jan
What???
0 * 5 != 5 ???
5 * 1 != 6 ???
Mark, I have reread your post from yesterday and I can tell you that many of your words and sentences are clear and sharp as a two-edged sword piercing the details of magnification definition. :)
The point is, that magnification is defined as a ratio between the apparent size of an object (size in an image) and its true size. All multiplicative factors you have mentioned (e.g. PPI), are in our two images approach, both in the nominator and denominator and therefore do not influence resultant magnification. They cancel out each other. ;)
A famous quote attributed to Leonardo da Vinci says: "Simplicity is the Ultimate Sophistication". ;)
Jan
Quote from: grepper on November 05, 2016, 04:23:12 AM
Herman – What is your guesstimate as to how those images compare to what you see @ 40X?
Here's the thing, since your magnification is entirely digital, it doesn't matter. You can always look at them on your computer and zoom in to your heart's content. Without optical zoom, though, you won't get any better resolution, meaning you won't see more detail.
I can tell, though, that you have a very narrow field of view. Just 2 mm. I can see about a quarter of a penny.
Herman, Yup. I understand optical magnification. Absolutely no problem there. I also understand that I can take a displayed image captured with no magnification ::) and compare it to an image captured at X optical magnification displayed on the same physical device, and determine the amount of magnification simply by measuring the display. That's not what I was getting at.
I also fully understand optical magnification vs digital zoom. Digital zoom on the capture device is, IMHO, less than worthless. You can always zoom later on the computer. In fact, depending on the complexity of the scaling algorithm, it can actually be misleading due to interpolation. Many sophisticated scaling algorithms will interpolate data so as to smooth edges, fill in holes, perform color equalization and reduce JPG artifacting so that the end product is more pleasing to the eye.
This can be desirable in photography when cropping and then enlarging an image for printing. Some of the sophisticated resizing applications such Perfect Resize specialize in it, and the scaling algorithms in Photoshop and the like do a most excellent job. It's rather amazing how much scaling you can do and still produce a reasonably good looking image. And that's not even considering the almost magical modern inkjet printheads, their control software and associated hardware, but I'm babbling.
But, you sure wouldn't want any of that "helpful" interpolation if you were looking for small anomalies in cell structure for example.
That is not the issue I was getting at. What I'm still trying to understand is scaling, either up or down, inherent in displaying an image on a particular physical display device with a physical pixel density and size. For instance, you cannot display a line with a thickness less than the physical width/height of a pixel on a display if you define a pixel to be the combination of its RGB elements. If you only illuminate the R for example, is the displayed pixel 1/3 the size? Not sure about that. Nonetheless, even if you could display a finer line with, say, color #0,0,FF, the closest object that could be displayed next to it would be one RGB pixel element away in which case it would appear to be a solid anyway. I'm rambling again.
Actually I happen to know that with computers at least all of this data is defined and accessible if you are willing to write some code or are using an application that takes advantage of it. A displayed object size can be device independent as long as it is not so large to exceed the boundaries of the display or so small that it cannot be represented with a single physical pixel.
The only reason I started thinking about this was when Jan said:
Quote from: Jan on November 04, 2016, 05:41:46 PM
Grepper, thanks for posting the image. If it is really 200X magnification than the edge is perfect. :)
Jan
That got me wondering if, when displaying an image of unknown original optical magnification, it was possible to figure out what the original optical magnification of the capture hardware was, not including sizing due to the interpolation of digital display devices.
My microscope has calibration software, and according to it, depending on exactly how close the lens is to the subject, the magnification is between 180X and 200X. The scope is rated at max 200X optical, focal length 5.8mm, FOV: 13.0°. Its specs correlate with the reported values from the calibration software. So guess what... I'm going to believe it. :) The images I post are ~200X magnification.
Grepper, you have confirmed that you are the foremost microscopist of our forum, congrats. :)
Having now all knowledge and understanding almost all mysteries, can you tell as what is the diameter of the splited hair shown in your reply #40? Was my row guesstimate 60 μm OK?
Jan
Quote from: grepper on November 06, 2016, 05:01:20 AMWhat I'm still trying to understand is scaling, either up or down, inherent in displaying an image on a particular physical display device with a physical pixel density and size.
The pixel size on the CCD is the limit of what you can resolve. You can magnify it all you want, but beyond a certain limit it won't help you identify anything in the image.
QuoteFor instance, you cannot display a line with a thickness less than the physical width/height of a pixel on a display
I think you can. If, for example, a line is narrower than the pixel width it may in some cases show up on the image as a line whose width equals the width of one or two pixels.
In Reply#54 I meant to say that I can see about a quarter of a penny on my scope. I think one of the designs of a dissecting microscope is a wide field of view.
Herman- I think your dissecting scope is perfect for looking at blades. It would be nice to have more magnification, but they have, like you say, a wide FOV and are set up for specimen lighting from above. They also have room for tall subjects.
The problem with biological scopes is that the objective lens must be very close to the subject and they don't have a lot of room for bulky subjects. They are generally set up for lighting from underneath for viewing slides, and are difficult to light stuff from the top or side. But they have higher magnification which is cool.
The problem with most USB scopes is that they are cheap, very fussy to focus, don't have a large FOV and the magnification changes depending on distance from the subject so you never know exactly what magnification the thing is set to. You just turn it all the way to "+" and assume it is acting to spec. Unless you spend a lot, they all have total junk for stands that makes focusing even more problematic. The good thing is that you can light from the top and sides, and since they are just a tube with a wire sticking out of them you can place them on any size object. Also, they are inexpensive and work good enough to be useful.
Quote from: Herman Trivilino on November 07, 2016, 02:11:26 AM
I think you can. If, for example, a line is narrower than the pixel width it may in some cases show up on the image as a line whose width equals the width of one or two pixels.
Exactly Herman! That's what's got me scratching my head. Even if the capture device was dense enough to resolve the line, the 96 dpi monitor resolution might not be able to represent it. In which case the the magic software interpreting the camera data for display would display a thicker line. Now multiply that by a 1920 horizontal pixel monitor display and the resulting error could be significant if you were trying to ascertain anything by measuring directly on the display.
Quote from: Jan on November 06, 2016, 01:55:25 PM
Having now all knowledge and understanding almost all mysteries, can you tell as what is the diameter of the splited hair shown in your reply #40? Was my row guesstimate 60 μm OK?
Jan
Jan- "Having now all knowledge and understanding"... Please stop. Surely you jest. :)
Sorry, I can't verify the hair size, but I will calibrate and do another one.
Why can't I verify the hair dimension? Because since images must be scaled to be attached to a forum post due to file size limits, or even as a direct link to Photobucket so they won't appear giant when displayed in the forum, I used a process that was as fast as possible to get the job done, without even having to load the image into some program to resize it. What I did was:
1. Display the captured image in an image viewing app with the shrink to fit option ON, maintain aspect ratio ON, so that the whole image would fit in the program window.
2. Grab the corner of the window and shrink it to some small size say, ~400 pixels wide by whatever, so it would be smaller.
3. Take a screen capture of the now smaller window.
4. Save the screen capture as a JPG file and either attach it to a post or upload it to Photobucket.
That was the quickest way I could figure out how to do it. It only takes a minute. While fast, it does mean that by the time the image is posted it has not only suffered scaling, but also JPG conversion with its associated "lossy" compression scheme with artifacting and image quality loss. But... it's a very expeditious way to reduce a 14MB+ image to 100KB or so.
Anyway, I looked around for the original image and can't find it. All I have is the little scaled ones that I uploaded. I can't find the hair laying around on my desk either. The Web sez: "the diameter of human hair to range from 17 to 181 µm". So you are right in the ball park.
As far as the whole magnification & displayed image thing is concerned, I don't even know if I'm asking the right questions or even what it really is I want to know! All I know is that, even though I don't know exactly what, something bothers me, and I know I don't understand what it means to capture on a CCD of some dimension and pixel density and then display it on a LCD of some other dimension and density with layers of hardware and software in between. While interesting, does it really matter? No.
But, I think I found the answer! Or at least something poking around whatever it is I wonder about. The only problem is that while stuff like the Nyquist-Shannon sampling theorem is apparently very explained, it is all so far over my head I'll never understand it. Oh, well.
http://biology.stackexchange.com/questions/36528/calculation-of-final-magnification-when-using-a-ccd-camera
I'm just happy to know that the images I post are ~200X .
Quote from: grepper on November 07, 2016, 06:22:02 AM
Jan- "Having now all knowledge and understanding"... Please stop. Surely you jest. :)
Mark, yes, it was said jestingly. I know that it is challenging to understand the basics of digital microscopy, namely the limiting factors for resolution. ;)
My situation is different from yours. The manufacturer of my LCD microscope guarantees that the total magnification 50X means that 1 mm object is shown as 50 mm on the LCD monitor. The other available optical magnifications are 125X and 500X. I do not use digital enlargement.
I do not care too much about the scope magnification because it is given by the combination of the magnification factor of the LCD eyepiece (12.5X) and the magnification of the objective (4X, 10X or 40X).
Nevertheless when I transfer the captured image JPEG file to the computer I am in a similar situation as you are. ;)
I understand that for you the scope magnification is important. In the past the magnifying abilities of the USB scopes were often overestimated. I am very glad to hear from you that for your scope all is in compliance with spec. :)
Jan
Quote from: Herman Trivilino on November 07, 2016, 02:11:26 AM
Quote from: grepper on November 06, 2016, 05:01:20 AMWhat I'm still trying to understand is scaling, either up or down, inherent in displaying an image on a particular physical display device with a physical pixel density and size.
The pixel size on the CCD is the limit of what you can resolve. You can magnify it all you want, but beyond a certain limit it won't help you identify anything in the image.
You are correct Herman, high magnification without sufficient resolution leads to empty magnification where no additional details about the sample can be seen.
The resolution is expressed in line pairs per millimetre.
Jan
P.S.: Grepper, attached is Leica's definition of magnification for digital microscopy.
I have finally managed to solve the microscope magnification issue for my purposes. Using the program CorelDraw I have prepared a scale bars of stated length that I superimpose on the image captured by the camera of the scope.
When an image is resized the scale bar is proportionally resized also. :)
Attached you can see the edge of a new Morakniv knife of carbon steel taken at magnification 125X and Tormek honing compound taken at magnification 500X.
Jan
P.S.: 0.1 mm = 100 μm ≈ 0.004" ;)
Good job, Jan. That makes the "road map" have meaning.
Jan- Thanks for finding that Leica explanation! That is exactly what I was thinking and wondering about.
It was the pixel size of the monitor with the pixel ratio of the montor/sensor that eluded me.
For example, with digital cameras you could have a 10mp 1/1.7" sensor, or a 1" sensor. Obviously, either the pixel size and/or density would be different between those two sensors. Now, transfer that data, 1-to-1 pixel to a 96 PPI LCD monitor. Then I started thinking there is the lens, (of some magnification?), focusing the optical data onto the camera sensor. It became a real head scratcher.
Anyway, the calibration and display software that comes with my scope, once calibrated, allows me to measure the distance between any two points regardless of all of that stuff. Really interesting to think about nonetheless.
Quote from: Jan on November 12, 2016, 02:43:39 PM
Attached you can see the edge of a new Morakniv knife of carbon steel taken at magnification 125X and Tormek honing compound taken at magnification 500X.
It would be interesting to see a 500 X magnification of same, so as to compare it to a 500X image of it sharpened with a 1000 grit wheel, and then another honed with Tormek compound.
From your 125 X image it looks pretty toothy, like at the factory it was sharpened with a fairly coarse grit.
This stuff can be a real time killer! :)
Is there room under your scope to take an edge up image?
Thanks for your responses, Grepper and Elden! :)
Leica explanation is the best I have found. Here is the link http://www.leica-microsystems.com/science-lab/what-does-300001-magnification-really-mean/
Grepper, my scope allows observations in reflected light only for 50X and 125X magnification.
I cannot apply a 500X magnification in reflected light, the objective is very close to the object, circa 2 mm and the object is not well illuminated by the incident light.
The magnification 500X I can use only for transparent samples illuminated from bellow (transmitted light). :-\
May be in the future I will try to dismantle the original scope table and modify the stage (mechanical desk with nonius) for knife edge observation purposes.
Jan
Thanks for that link. Amazingly appropriate. You da man, Jan!
You are welcome, Mark! :)
Jan
My USB microscope took a self portrait!
Whenever I look at this I feel the urge to say, "Open the pod bay doors please, Hal".
Definitely better incident light illumination than I have! :)
From the true distance between the LED diodes you can construct a scale bar for your microscope images. ;)
Jan
Yeah, that's the advantage of a USB or dissecting scope over a biological scope. But then USB scopes are generally rather cheap and have other issues, and dissecting scopes are generally low power. It would be nice to have a mash of the best of all three!
I had an 800 X USB scope once that I returned because it came with some crud on the inside of the lens. (It was specially manufactured in, and imported from the Orient). It did seem to work OK, but had an extremely small FOV and focusing was a hair pulling freak show because it must be held perfectly steady on a rock solid stand and it came with no stand. Just a tube with a wire sticking out of it. Add that to a depth of field about as deep as a hair and you kind of get the frustration when using one. You can pick one up to play with for on $29.00 or so. Very inexpensive. Might be worth it just to play around with again. Strapping one to the quill of a milling machine or drill press would probably make a nice stand. :)
Quote from: Jan on November 13, 2016, 11:09:05 PM
From the true distance between the LED diodes you can construct a scale bar for your microscope images. ;)
Here you go Jan. :) Full FOV image.
Download full size JPG of original BMP. https://www.dropbox.com/s/tvm4y9grflz5llj/ff.jpg?dl=0 Press the DOWNLOAD button upper right corner of the screen. At the bottom of the annoying JOIN UP dialog click No Thanks Continue with Download.
FWIW; 600 grit grind, lightly stropped with Tormek Honing Compound. It looks kind of scratchy but easily shaves arm hair, push cuts paper, glides through onion skin at very thin angle, etc. A nice, sharp blade that will work well for general food cleaving tasks.
Congrats Mark, you have not only a scale bar but you can also add dimensions to selected features of the captured image. I think that is all what we need for our edge inspection activities. :)
Your FOV is significantly larger than mine at 50X magnification. My FOV is circa 1.4 mm wide for 50X and decreases to some 0.56 mm for 125X magnification. ;)
What concerns your edge's, I think your grinding and stropping is uniform, the burr is flawlessly removed and no deeper scratches are reaching to the cutting edge. Nice edge, no wonder that it has performed well in all your tests. :)
Jan
Moved to General Questions.