Polishing angle calc

[RickKrung]

...snip....
My 2 cents (and I don't think I'm alone here)... measuring directly to the wheel is the better route.  It's quick, easy, accurate, and machine independent.  No matter what configuration: horizontal, vertical, FVB, etc., or even if you transition to another machine like a buffer with a honing wheel of some sort, you're good to go.

I've gone the route of "measuring to the machine"... and it just causes me unnecessary work, and I don't see any better result.  Measuring to the machine is just a step added after measuring to the wheel, (with a bunch more measurements you now have to account for).
...snip...

CB is right about measuring directly to the wheel.  It eliminates all of the unnecessary measurements and associated error, except two: 1) the one direct measurement and 2) alignment of the measurement probe with the centerline between the USB and machine shaft.  A major benefit is that machine independent.

I tried it recently and was a little bit plagued with No. 2.  I tried eyeing its alignment, but found I did better when I placed a straightedge (metal ruler) to indicate that "correct line".  I have in mind to make an easy jig, but alas, just too much other stuff going on.  I was also getting inconsistent angles.  I'm sure there is something wrong with my technique, because it should be much more consistent.  For the meantime, I've gone back to measuring to the top of the machine case.

Rick

[cbwx34]

CB is right about measuring directly to the wheel.  It eliminates all of the unnecessary measurements and associated error, except two: 1) the one direct measurement and 2) alignment of the measurement probe with the centerline between the USB and machine shaft.  A major benefit is that machine independent.

I tried it recently and was a little bit plagued with No. 2.  I tried eyeing its alignment, but found I did better when I placed a straightedge (metal ruler) to indicate that "correct line".  I have in mind to make an easy jig, but alas, just too much other stuff going on.  I was also getting inconsistent angles.  I'm sure there is something wrong with my technique, because it should be much more consistent.  For the meantime, I've gone back to measuring to the top of the machine case.

Rick

I'm sure by now you've seen the "Angle Tool" (but here it is for those that haven't)...


https://forum.tormek.com/index.php?topic=4170.0

... that makes setup pretty easy and easily repeatable.  I mainly use a caliper... it's what I practiced with, and just like anything, with a bit of practice, you can get accurate consistent results.  (I seem to recall you spending some time dialing in the accuracy measuring to the machine, in my mind, no different).

[RickKrung]

...
I have in mind to make an easy jig, but alas, just too much other stuff going on....snip...

Rick

I'm sure by now you've seen the "Angle Tool" (but here it is for those that haven't)...


https://forum.tormek.com/index.php?topic=4170.0

... that makes setup pretty easy and easily repeatable.  I mainly use a caliper it's what I practiced with, and just like anything, with a bit of practice, you can get accurate consistent results.  (I seem to recall you spending some time dialing in the accuracy measuring to the machine, in my mind, no different).

CB!  Thanks for shaking my tree.  I had of course seen postings about this tool but never paid it any attention...   ... thinking "Oh, I don't need that"...   

What a brilliant tool.  It is extremely close to what I was imagining.  I just ordered one.  It will save me a lot of time and aggravation trying to reinvent this wheel. 

The slot for the collar is a nice touch.  I wasn't impressed with how the jaws got dragged across the stone while removing to measure the diameter.  But with care, it probably can be used without wearing down those jaws too much.  I'll find out. 

Thanks again,

Rick

[BobD]

Rick,

Would something like this help find the center line? Not sure if I'm misinterpreting what you're looking for

[BobD]

Oops, sorry nevermind. I didn't notice CB  already addressed this with a solution.

Also, while I'm here...
Gilles, thank you for sharing your work. It's a great addition and very much appreciated

[cbwx34]

Rick,

Would something like this help find the center line? Not sure if I'm misinterpreting what you're looking for

Good idea!  In fact, it made me think that just adding a string to the end of the caliper, could easily improve the accuracy...



... or at least help during the "practice phase".

[Jan]

I also use the USB top to stone distance because is simpler and more universal approach.

Jan

[Ken S]

I believe a generally accepted history of using trig too simply knife bevel setting on this forum began with Dutchman's booklet about grinding angles.

The next development was my kenjig. I recognized that using Dutchman's tables offered a more precise alternative to trial and error for setting up knives. Admittedly, I designed the kenjig for simpler times. At the time, knives were generally sharpened with one grinding wheel, the SG-250 (or SG-200 for the T4). Most kitchen knives were sharpened with 15° double bevels. I made provisions for wheel wear, increasing the Distance by 1 mm for every 10 mm of wheel diameter wear. I made a second kenjig for 20° double bevels, but rarely used it. Nobody was using CBN or diamond wheels at that time. I was (and still am) using Henckel kitchen knives and garden variety pocket knives. I was not thinking about sharpening exotic knives.

Dutchman used a combination square for his set up. I used a kenjig made of 12mm Baltic Birch Plywood. We both measured Distance from the top of the support bar to the arc of the grinding wheel. I use the same measurement for any Tormek model and for both vertical and horizontal positions. Later, more sophisticated programs measure from the support bar to the frame of the Tormek. Some claim this is more accurate. This may be so, although I have never understood why.

My kenjig thinking continues to evolve. For years, it has been based on 15°. Based on Wootz' ongoing research, I plan to switch to 12°. Also, I have been recently considering my fixed Projection of 139 mm. Dutchman fixed the Distance and adjusted with the Projection. Wootz' original setting block has spawned several interesting setting blocks. Diamond and CBN wheels donot change diameter, making wear correction increasingly obsolete.
o
I also realize that we have many different expectation levels in our sharpening. What it comfortable for one may not work well for another. What fit me well last year may not fit next year. As always, I believe we are best served by understanding several techniques and growing.

Ken

[John_B]

Ken, I think once you start sharpening your kitchen knives to 12° and honing around 13.5° you may change your mind on what is sharp enough. I too made this change on kost of my my personal knives some time ago.

Trimming a large piece of meat in preparation for the smoker or slicing vegetables is a real joy. Pay careful attention to safety best practices. Last Fall I cut a finger quite badly while trimming a large pork butt for pulled pork. I did not feel the cut but saw blood. You can also impress family and friends by s;icing tomatoes and grapes one  handed. I do recommend keeping a meat cleaver or heavy kitchen knife sharpened to 20° + for times when you need to chop bone.

[Ken S]

John,

The great photojournalist, Alfred Eisenstaedt, encouraged photographers to make a good photograph, and then make a better one. I have always felt that the present kenjig was and is a good method. However, I believe you are correct in believing that I may change my mind as to what sharp is as I explore 12° bevel and 13.5° honing. I want to be open minded for growth.

I will post when I reach significant points along the journey.

Ken

[cbwx34]

Rick,

Would something like this help find the center line? Not sure if I'm misinterpreting what you're looking for

Good idea!  In fact, it made me think that just adding a string to the end of the caliper, could easily improve the accuracy...

... or at least help during the "practice phase".

I found a digital caliper on sale for $9.99, so got it and glued a small strip of metal to the end...



... makes for a pretty accurate setup.  (Might need a better way to attach it eventually, if want it to be permanent).... 
(and now I can use metric). 

Edit to add:  Didn't think about it at the time, but on the leather wheel side, putting the metal strip behind the locking knob  works.... just making some quick comparisons... easily less than a degree difference.



(Also, I just used a couple of drops of superglue... I imagine someone here would have a better solution)?   

[Jan]

The Excel script Polishing Angle Calc is really useful tool. Recently I used the sheet Thick Tapered Knife Edge to quantify the impact of blade thickness on the bevel angles.

I assumed flat 4.5 mm (0.18") thick blade mounted in knife jig with projection distance of 139 mm and the USB set up geometrically for the grinding angle 15⁰. The script revealed that instead of the desired grinding angle 15⁰ we will get 15.5⁰ for the jig in the Up position and 14.5⁰ for the jig in the Down position. So the discrepancy between the desired grinding angle and the real grinding angle is 0.5⁰ for each side and does not depend on stone diameter or the magnitude of the grinding angle.

This has important consequences for advanced, jig guided, deburring. Assuming that the deburring wheel was geometrically set up to 16.5⁰ in reality we will hone 17⁰ for the jig in the Up position and 16⁰ for the jig in the Down position. It means that despite the fact that the bevel angles are slightly biased the deburring of each site will be done as intended. 

Jan

[cbwx34]

The Excel script Polishing Angle Calc is really useful tool. Recently I used the sheet Thick Tapered Knife Edge to quantify the impact of blade thickness on the bevel angles.

I assumed flat 4.5 mm (0.18") thick blade mounted in knife jig with projection distance of 139 mm and the USB set up geometrically for the grinding angle 15⁰. The script revealed that instead of the desired grinding angle 15⁰ we will get 15.5⁰ for the jig in the Up position and 14.5⁰ for the jig in the Down position. So the discrepancy between the desired grinding angle and the real grinding angle is 0.5⁰ for each side and does not depend on stone diameter or the magnitude of the grinding angle.

This has important consequences for advanced, jig guided, deburring. Assuming that the deburring wheel was geometrically set up to 16.5⁰ in reality we will hone 17⁰ for the jig in the Up position and 16⁰ for the jig in the Down position. It means that despite the fact that the bevel angles are slightly biased the deburring of each site will be done as intended. 

Jan

Can you expand on this ("does not depend on stone diameter")... I thought that's why it was created... because of the difference in wheel size? 

[Jan]

CB, you are talking about the sheet Polishing Angle, but I am talking about the sheet Thick Tapered Knife Edge.

In my example the honing angle is by 1.5⁰ larger than the grinding angle and for all realistic wheel diameters there is no danger that heel of the bevel could collide with the honing wheel. (I assume that the honing angle is larger than the minimum grinding angle.) 

The results from the sheet Thick Tapered Knife Edge clearly show that thick blade is source of bevel angle asymmetry which does not depend on stone diameter or the magnitude of the grinding angle. The consequences are important, both, the real grinding angle and the real honing angle are biased in the same way. This allows successful deburring despite the fact that the bevel angles are biased.

Jan

[Gilles]

Hi Jan,
This is exactly the conclusion that I have done from this study and you explain it very well: "The consequences are important, both, the real grinding angle and the real honing angle are biased in the same way. This allows successful deburring despite the fact that the bevel angles are biased. "

It is also interesting to notice the effect of thickness and the effect of tapered blade on the bevel angle asymmetry (grinding angle and bevel height).

Tapered blade angle have often more impact than the blade thickness itself. The thicker the blade is, the higher the tapered blade angle can be and the higher the asymmetry can be.

Gilles