I've never had any luck sharpening utility knife blades. I looked at a new one under the 40X microscope and it has a micro bevel on it that's maybe 0.1 mm wide and has a more refined scratch pattern. Once you know it's there you can see it as a shiny strip along the cutting edge using magnifying glass or even with the naked eye.
Do you mean the metal handle ones with the thumb button that slides the blade up and down? I've gotten those so they seem sharper than when they were new. But then maybe I just go use to dull blades!
Must be fun having a microscope!
Herman, you had mentioned that there were some knives that you just could not get sharp, and I'm curious if the microscope showed why. Do you know what was happening with them? Are they sharp now?
I think I'm going to have to get a microscope.
Utility blades have not been a problem with me. They have a straight edge like a chisel. My biggest problem is that they are full of sticky junk (from slicing adhesive tape). Also, the metal is removeable by grinding and I have no problem putting on a new angle. Maybe you can try another brand
Quote from: grepper on April 08, 2013, 06:33:49 AM
Do you mean the metal handle ones with the thumb button that slides the blade up and down?
Yes. Made by Stanley.
It is fun having a microscope. It's been a while since I tried sharpening a utility knife blade, so maybe I'll have another go at it.
I haven't been able to figure out why I can't get some knives as sharp as others. I believe it is due to the fact that some steel is harder to grind and to form a burr. It takes more skill to sharpen knives made of these tyes of steel, but I don't know if that's the whole story.
I'll keep you posted as I conduct my experiments.
Last night I remembered I had a knife blade that I hadn't sharpened. Some years ago my daughter got me one of those Gerber tools that has a pair of needle nose pliers, a saw, screw driver, and so forth all in a small portable device that fits in a belt pouch.
I looked at the knife blade and tested it for sharpness. It has one small nick near the tip but otherwise would slice through paper but not shave hair too well. I decided to take the Tormek honing wheel to it. It made the edge shiny, the scratch pattern remained but as usual the metal between the scratches was smoother. It improved its ability to slice paper and shave hair.
Quote from: Herman Trivilino on April 08, 2013, 02:59:27 PM
I haven't been able to figure out why I can't get some knives as sharp as others.
Did you put one of those knives under the microscope to try and see what is actually happening? I know for me at least, when that happens I stick with a rougher wheel longer, turning the knife frequently. Sometimes it seems to take a lot longer, even at 300 grit, than I would think.
On very dull knives I get the idea that it's taking a while to actually make the hollow bevel caused by the wheel, and when the thing is not getting sharp I'm guessing that I'm not getting to the actual edge. It would be so cool to actually see and understand what what happening then.
I will be interested what you find out when you scope one of them!
Quote from: grepper on April 08, 2013, 05:40:46 PM
On very dull knives I get the idea that it's taking a while to actually make the hollow bevel caused by the wheel, and when the thing is not getting sharp I'm guessing that I'm not getting to the actual edge. It would be so cool to actually see and understand what what happening then.
Yes, Mark, I have verified with the scope that that is exactly what's happening.
However, even when I'm sure I've ground all the way to the edge and eliminated the burr, some knives are just sharper than others. I'm thinking it's the quality of the steel and edge angle.
To rephrase what Ron Hock said, I've come up with three questions you ask about a knife.
1. Is it corrosion resistant?
2. Is it easy to sharpen?
3. Does it hold an edge well?
You can get an emphatic "yes" to, at
best, only two of those three questions.
So, for example, today a friend has brought me a knife to sharpen. It's obviously highly corrosion resistant as it's a kitchen chef's knife and despite years of use is almost as shiny as chrome and the surface is uniform in appearance with no discolored spots or portions. It's had it's edge broken off along most of its length because he attempted to sharpened it with one of those cheap devices like you might see on the side of an electric can opener. But in the places where the edge is not broken it appears to still be pretty sharp.
So my guess is that this is hard and brittle steel meant to hold an edge well. If my theories are correct this will be a difficult knife to sharpen. We shall see when I give it a try tonight.
2. Is it easy to sharpen?
3. Does it hold an edge well?
I miss the hunting knife I had as a kid. It was rusty. The leather handle was moldy. But it was sharp and easy to sharpen. I sharpened it on the bottom of a crock pot, I sharpened it on a stone in the wild.
The only thing I have like that now is my Gransfor axe. I used it to chop up 4 lobsters for the fire last year. I saw it rust right before my eyes in less than 15 minutes in seawater (from the lobsters). Polished it right up immediately. Some discoloration but not bad. I can live with it.
Herman
What jig do you use for the utility knife blades?
(The amount of blades I've used over the years - short use and then binned - would have paid for a few Tormek jigs!)
I use the small knife jig for the utility knife blades. Works fine. The SVM-45.
Quote from: Rhino on April 11, 2013, 11:43:33 PM
I use the small knife jig for the utility knife blades. Works fine. The SVM-45.
At what bevel angle?
Regarding the bevel angle, I don't remember but I thought there was no problem if you use the small knife jig and clamp at the first stop. I hope to have time to check this weekend for you.
I was also thinking, if you want to take a lot of the human skill out of this, you can clamp the small knife jig into the chisel jig. I'll check this weekend to see if it is possible too.
When you refer to the small knife jig are you still talking about the SVM-45 or the new SVM-00?
I should have been more clear. I was referring to the SVM-45.
My utility blades are trapezoidal and .75 inch from the sharp edge to the non sharp edge.
As I said earlier, I remember clamping it to the SVM-45 and sharpening it. I'll double check this weekend.
I am looking at my utility blade right now. It is wider (from the sharp edge to the non sharp edge) than my paring knife or about the same as my paring knife. I certainly sharpen my paring knife many times with the SVM-45 so I don't see sharpening a .75 inch utility blade as being difficult.
I do plan on measuring the angle for you this weekend if I can get to it. I'll try putting the SVM-45 (with the utility blade) into the chisel jig too. Just for fun.
I would be delighted if Rhino could provide some set up settings and angles. I have just got my SVM45 and done some spokeshave blades as posted elsewhere, including my scary moment!
I didn't have time to do it properly, but I also had a go with a trapezoidal utility knife blade, 0.75 inch deep.
If I pushed the blade against the stops inside the SVM45, I didn't have enough blade protrusion to use the angle master. If I mounted the blade protruding a bit more, there was barely enough for the angle master and also when sharpening, the tips of the blade were flexing. This resulted in the centre area of the edge being ground more than the tips, so a slightly concave edge. (Not a critical point on a blade which will probably just be used for somewhat imprecise work!)
I couldn't get the jig set up so that I was grinding the full depth of the original bevel. I was in danger of grinding the front of my just paid for jig! I did manage a very small depth bevel, on both sides, and it was certainly sharp.
Strongly advise that anyone trying small width blades to sharpen away from the edge - see my scary moment elsewhere!
Quote from: Rhino on April 12, 2013, 07:45:22 PM
I am looking at my utility blade right now. It is wider (from the sharp edge to the non sharp edge) than my paring knife or about the same as my paring knife. I certainly sharpen my paring knife many times with the SVM-45 so I don't see sharpening a .75 inch utility blade as being difficult.
I can't figure how that's possible. You must be grinding at a very large bevel angle.
I messed around with a blade from a Husky folding utility knife. It is a little smaller than the regular size utility blade. It is marginally workable in the SVM-45. I have barely gotten into the jig along the way. If the blade is positioned perfectly (quite a ways out from the stops), the wheel doesn't get into the jig.
I had to shim the blade as the thickness was too thin for the jig to clamp the blade. Used a couple thicknesses of thin cardboard for clamping. The shims need to be a little thicker as the blade could still move at times, hence the wheel getting into the jig.
The bevel angle is very close to the original bevel. I used the permanent marker approach.
If I was really serious about doing utility blades, I would probably make a permanent shim that would form an extended stop for the back of the blade to be against, as well as for the thickness.
I think the regular size blades should be easier done due to the larger width of the blades.
I have spent some time today trying a couple of utility blades. They are 0.63 mm (0.024") thick; 61.5 mm (2.42") the long side of trapezoid, 33mm (1.3") short side of trapezoid and 19mm (0.75") front to back.
The bevel is 2.52 mm (0.1") wide.
As the blade is 19mm front to back, when it is inserted fully into the SVM45, the amount protruding is 6mm ( 1/4 ").
Setting the SVM45 to the zero position on its adjustable stop, and moving the universal support bar up and down it was not possible to align the back of the blade bevel with the stone (as per Tormek instruction sheet). This was due to the SVM45 fouling the wheel. So I made the best bevel contact I could with the SVM clear of the wheel. There is insufficient blade protruding to use the angle master properly. Marked the bevel with marker pen and started up the machine. The front edge of the bevel started to shine up. Turned the jig over to do the other side, and lo and behold, it started to grind the sloping face of the SVM45!!!!!!
Reset it so that the angle was slightly steeper and both sides of the SVM would be clear of the wheel and had another go, and got bevels about 1mm wide.
I got a re-sharpened blade, but wasn't convinced it was as good as an original. There is some difference along the edge of the blade due to the freehand element involved when using the SVM45.
I then started doing a technical drawing to see what minimum angle could be achieved using the same utility blade without fouling the SVM45 on the wheel. Then it occurred to me what is the original bevel angle that I am trying to match?
With blades 0.63mm thick, and a bevel width of 2.52mm, this calculates as 7.12 degrees or an edge angle of 14 - 15 degrees.
I don't think it's worth the effort considering the price of new blades, but I know I can get out of a hole if I was stuck for a usable blade.
Quote from: RobinW on April 14, 2013, 12:17:58 AM
With blades 0.63mm thick, and a bevel width of 2.52mm, this calculates as 7.12 degrees or an edge angle of 14 - 15 degrees.
There's a microbevel that you can't see with the naked eye.
I've got a pack of Stanley blades (double ended) that I bought with a Stanley knife in 1989, I'm down to the last blade (first side). I think there were ten in the pack originally. So 2013-1989 that's 24 years for let's say £5 in cost
Those blades have cut bitumen roofing felt on three shed roofes, cut plasterboard in two house renovations and all manner of woody things over the years
For me, I'll buy new ones when the last one finally expires. I don't think the Tormek is right for some jobs. This is probably one of them
We used to go through them a lot faster than that on a carpentry crew. It was really the only tool we usually carried that had a sharp edge on it, and so it got used for all manner of things. A nail can be used, by the way, to change the blades. No screw driver needed. Just place the head of a common nail in the screw slot and turn the nail.
I don't believe the Tormek can be used to come anywhere near the sharpness of a new one. The bevel geometry is complicated, the edge angle is small, and the edge itself is very true.
You may be right Herman that maybe you can't get them sharp as new, I don't know, but they fit into the knife jig just fine as I remember, and I was able to get them very sharp. They were dull, but now they seem really pretty sharp. Plenty good enough so you won't think they are dull. I don't remember it being any sort of a problem. I don't use them much, so for me it worked out great.
I would suspect if you used them every day and went through a pile of them, it might not be worth sharpening them and just switch them out with new ones.
You must have barely inserted them into the SVM-45. I don't recall having done that, but it was some time ago that I tried to sharpen them.
Thanks everyone for sharing.
I got the Tormek out. It was a busy weekend so I did not get to do actual grinding but it help bring back my memory. I don't have a permanent setup for my Tormek so it takes me a little longer to set up the system. Another disclaimer, I am just telling you what I did and I in no way recommend anyone follow. You have to make your own decision as to safety. Once I saw the system the memory came back.
I used two blades as support (I call them support blades from now on). Stuck them all the way into the back of the SVM 45. Then I put the blade I wanted to sharpen between the two support blades. That gives you enough thickness to clamp. I clamp about 1/3 of the utility blade (the blade I want to sharpen into the SVM45 only. Roughly until the U shaped cutout just disappears behind the SVM45 clamp. You can't really see this because the two support blades would block your vision. But I am just giving you an idea.
To align the utility blade with the SVM45, I use a transparent ruler placed against the SVM45 and I align the blade to be sharpened to it. I won't go into details since you probably have your own aligning method.
Then I put my SVM45 against my grindstone which I seem to recall is about 243 mm diameter. I measured about 12 to 14 degrees with my angle device. Meaning, at least to me, I seem to be able to grind at 15 degree or 20 degree.
I don't remember grinding with the stone coming towards the blade or away from the blade back when I did it. I did not grind this weekend, just checked the setup. My guess is that I would have ground with the stone coming towards the blade. Since I can set a 20 or 15 degree angle, it is not a problem. On my setup, I can flip the SVM45 and sharpen the other side easily.
It was an intellectual exercise and I remember the product being as sharp as a new blade. But then, utility blades are not ultrasharp. My kitchen knives are sharper.
I was not too worried about the fine points of blade angle or symmetric grinding although I think it can be achieved if you measure carefully and grind without putting too much pressure to distort the blade or the clamping setup. I did it for fun a while back. Come to think of it, utility blades make good shims. I'll dull a few used ones the next time to use as shims on my SVM45.
I will continue to buy utility blades instead of sharpening them.
Excellent innovation there, Rhino. I can see how that would work nicely. If ever I need to sharpen one I'll do it that way. It'd be interesting to see what the edge looks like under a microscope.
I've used two strips of metal clamped into the knife jig to produce an extended thin clamp a bunch of times with small bladed knives. For the most part it seems to work well enough even though on some blades they have a tendency to pop out. But then on small blades, I don't find it necessary to have a completely firm clamp, just some assistance from the jig to hold the bevel angle. It just requires a little practice, skill and understanding the setup, but then it works just fine.
If the SVM-45 was just a little thinner with a less obtuse angle at the end of the clamp, it would solve a lot of the small knife problems. I guess it's the size that it is for strength owing to the fact that it's aluminum. I've wondered if a thin, possibly titanium grip for the end of the SVM-45 might work.