Differential bevels

[Scotty]

I have been attempting to upgrade my skills and equipment following Wootz's book and web site.
Initial results are positive with the exception of my bevels.
One side is noticeably wider than the other.
My test blade is over 2x thicker than the SVM45 offset which I suspect is the problem.
If I understand Knife Grinder's recommendations, I need to have several SVM45s, each with a different degree of increasing machined offset.
Assuming I can find a qualified machinist, this could get cumbersome quickly.
I believe I can deal with very thin blades by using painters tape, but too thick evades me
Looking for some advice on how to deal with this issue.
Thanks

[Ken S]

Good question, Scotty.

Wootz' solution of having several modified SVM-45 jigs and some feeler gages is certainly a workable choice. Is it the only choice?

I do nor recall the issue of different thicknesses of knives particularly being an issue until it was discovered by Wootz several years ago. I have several editions of the handbook. I don't remember reading about problems with different thicknesses of knives. The SVM-45 has undergone several modifications over the years, the earliest I know of being in 2002. I am surprised that if Tormek thought having the jig self centering that this feature was not incorporated into one of the modifications.

The first alternative which comes to mind is sharpening one side of the knife, then remounting the knife facing the opposite direction and then grinding the other side. This may not be as clumsy as one might think. Assuming that you use protective tape, mark the outline of the clamp on the tape. This makes it easy to realign the jig exactly for the second side of the knife. If you start grinding with the SG graded fine, only one flip should be needed.

Regardless of what you choose with your knife jig, I recommend finding a good local machinist. From time to time, you may want some machining done. Most of us have neither the skill nor the tools to do this.

More to follow. For now, I want to watch the online sharpening class.

Ken

[cbwx34]

...
I do nor recall the issue of different thicknesses of knives particularly being an issue until it was discovered by Wootz several years ago. I have several editions of the handbook. I don't remember reading about problems with different thicknesses of knives. The SVM-45 has undergone several modifications over the years, the earliest I know of being in 2002. I am surprised that if Tormek thought having the jig self centering that this feature was not incorporated into one of the modifications.
...

Ken

You're kidding right?  So, it's now a "known" issue... yet still nothing from Tormek.  Here's my theory...

...they ignore it, like they do most other issues involving knife sharpening.  (I was going to post a picture of an ostrich)...

(I know your next 'excuse' will be cost)... 

I have been attempting to upgrade my skills and equipment following Wootz's book and web site.
Initial results are positive with the exception of my bevels.
One side is noticeably wider than the other.
My test blade is over 2x thicker than the SVM45 offset which I suspect is the problem.
If I understand Knife Grinder's recommendations, I need to have several SVM45s, each with a different degree of increasing machined offset.
Assuming I can find a qualified machinist, this could get cumbersome quickly.
I believe I can deal with very thin blades by using painters tape, but too thick evades me
Looking for some advice on how to deal with this issue.
Thanks

There are a few other options...

You can adjust the blade stop or USB height each time you flip the knife... not ideal but doable.  You can also tape one side of the clamp, when you do a thicker knife, so that it equals out.  (Someone made a sleeve that was thicker on one side, but I can't find the post right now).

You can use an alternative clamp... something like a Lansky clamp, that will self center the knife. 

You can use make/use a "platform jig" instead of the SVM-45.

Probably a couple others I can't recall right now.

Edit: Oh yeah... you can learn to sharpen them freehand, without a jig.

[RickKrung]

I have modified three medium knife jigs (SVM-45) according to Knife Grinder's methods and use shims.  I like this system, but it is not an option for many/most due to the cost of the several jigs and finding someone to modify them.  I can do this because I am a machinist. 

I have not tried, but like the idea of adjusting the stop collar when flipping to the other side.  As CB says, not ideal, but doable.  I think more efficient and probably more effective than flipping the knife in the jig.  I suspect definitely faster and easier.  This is what I would try, if I did not already have the modified jigs.  In attempting this method, I think I would figure out how much rotation the collar needs to change from one side to the other and standardize on a simple method of rotating it precisely that much between sides (checking the distance occasionally, maybe on one side only), in an attempt to simplify and speed up the process yet maintain consistency of the angles for each side.  This is likely a trial and error thing, probably using the black marker on the bevels, as I don't know how one would "set" the different angles quickly. 

Another option might be to have two USBs, with two Micro-Adjust nuts on each, these being used to "lock" their position. Then, switch between the two USBs when flipping sides.  Might be slightly slower than rotating the collar, but possibly more consistent in maintaining the angles on the respective sides.  Again, likely a trial and error process, with the black marker, finding the right USB heights. 

I tried the Lansky.  Didn't like it.  Too flimsy and I had difficulty getting it to grip the blade tightly enough. They are cheap enough to give a try, however, as others may find they work well.  They are self-centering. 

Rick

[Scotty]

Thanks for all the replies.
Good advice from everyone.
Not that it really matters, I used to be be a fair freehand sharpener, but I sustained some nerve damage that precludes me from holding/sustaining a reasonable constant angle - ergo, Tormek.
I am interested in the online class.
Where might I find that information?
I assume that it is different from the multitude of You Tube videos.

I do have two SVM45s.
I suppose a third is not out of the question..
Rick, do you have the machining specifications?

[John_B]

https://www.youtube.com/watch?v=R2ifZQOJA7k

This is the link to the first Tormek class. Today's class on scissors and axes has not bee posted yet. If you go to Tormek's channel on YouTube there are more videos.

On you tube there are a number of good videos, however, there are quite a few that demonstrate what I would term "not best practice" so as they say let the watcher beware.

[micha]

I think it has been posted:
https://www.youtube.com/watch?v=QlScXCdisAo

[jvh]

Hello,

I use this procedure to approximately center the knife in the jig and then I make fine adjustment with eccentric bushing.

Very rarely (really thick knives) is necessary to use a shim between the blade and the jig. Also it's possible to change protrusion length with adjustable stop to get the same angle on both sides of the knife when flipping the jig, but it's not very comfortable.

You can modify knife jigs according to Knife Grinder's methods but you get a dedicated solution for a specific knife thickness. I didn't go this way, so now I have four universal SVM-45 jigs and I can grind more knives on one wheel, then change to another and continue...


jvh

[RickKrung]

...snip...
You can modify knife jigs according to Knife Grinder's methods but you get a dedicated solution for a specific knife thickness. ...snip...
jvh

The above statement is not correct.  It missed the major point of the modification, which is the use of shims to center blades. 

KG's modified jig solution relies on the use of shims to center the blade within the jig.  Actually, this works for unmodified jigs as well, if the blades are thinner than the nominal thickness that does center.  It is true that if the shims are not used, a modified jig is really not much better than an unmodified one, as it will have a very narrow range of blade thicknesses that will be relatively centered. 

I shortened a set of stainless steel shims for use with my modified SVM-45s so they don't protrude too much and interfere.


For the long knife jig (SVM-140) I use non-shortened shims, but I have not modified the -140.  I do use the longer shims with the -45s if the blades are long and the shims don't interfere. 

I can set thin blades to centered in the most extremely modified jig (#3) as easily as the less modified jigs, using my table of shim thickness.



Rick

[jvh]

The above statement is not correct.  It missed the major point of the modification, which is the use of shims to center blades. 

KG's modified jig solution relies on the use of shims to center the blade within the jig.  Actually, this works for unmodified jigs as well, if the blades are thinner than the nominal thickness that does center.  It is true that if the shims are not used, a modified jig is really not much better than an unmodified one, as it will have a very narrow range of blade thicknesses that will be relatively centered. 

That's true. If you use shims then it is so. I see such artikel on KG's pages, but the problem is that I didn't see any shims in KG's videos. But I didn't see all and maybe all presented knives have ideal thickness.

Sometimes I use shims too, as I mentioned above, but working with them is not very comfortable for me and it takes more time. I don't need whole set, actually I use 2 sizes because eccentric bushing allows me to make angle correction easily. There is also a problem with shims if the blade does not have parallel sides (eg. full flat grind) because bottom jaw of the SVM-45 jig is fixed which affects the clamping angle.

Point was that I need only this eccentric bushing as addidion to standard SVM-45 or SVM-140 jig (and small allen key for setting).


jvh

[van]

Sorry but another solution could be to use a laser line on the stone. When turning the jig, the blade (in + or -) can be realigned on the laser line using the adjustable handle.

[Scotty]

Good point, and certainly an option to consider.
I saw a video about someone doing that.
Not sure how that would work though.
My jig length (overall) did not vary.
The only thing I can see, given constant jig length, wheel diameter, and support bar height would the angle in the jig.
I am probably missing something obvious.
Thanks

[jvh]

Sorry but another solution could be to use a laser line on the stone. When turning the jig, the blade (in + or -) can be realigned on the laser line using the adjustable handle.

Could be. Laser is good as reference point/line when grinding curved blades and turning with the jig right and left.

I din't try it for angle correction via protrusion length change when flipping the jig on other side, because eccentric bushing has also an advantage that can be used as a stop for the adjustable handle. So I have the stop for one side and if I flip the jig to other side I just turn the adjustable handle about measured step (eg. 3/4 turn). Very easy, accurate and applicable to different wheels without re-setting the laser (if wheel diameter differ).

My jig length (overall) did not vary.
The only thing I can see, given constant jig length, wheel diameter, and support bar height would the angle in the jig.
I am probably missing something obvious.

That's correct if you have the knife edge correctly centered in the jig. If not, you will get uneven grind.
Uncentered clamping you can compensate by eg. protrusion length correction (via adjustable handle), but it can be source of mistakes if you forget to change the length when flipping the jig. Therefore is centered clamping always preferred option for me.

You can easily check correct clamping with Aglemaster:
1) Put the jig with the knife on the stone.
2) Set desired grinding angle (or copy the set one).
3) Flip the jig (keep the same part of the blade on the stone).
4) Check the angle on the other side (on the opposite part of the knife as in point 2)
5) If the angles are the same on both sides, your edge is centered.


jvh

[RichColvin]

Hello,

I use this procedure to approximately center the knife in the jig and then I make fine adjustment with eccentric bushing.

Very rarely (really thick knives) is necessary to use a shim between the blade and the jig. Also it's possible to change protrusion length with adjustable stop to get the same angle on both sides of the knife when flipping the jig, but it's not very comfortable.

You can modify knife jigs according to Knife Grinder's methods but you get a dedicated solution for a specific knife thickness. I didn't go this way, so now I have four universal SVM-45 jigs and I can grind more knives on one wheel, then change to another and continue...


jvh

I've used the eccentric bushing approach.  Works well.

Rich

[Scotty]

I am interested in the eccentric bushing -and also the SVM45 clamping knob modification that jvh has made.
I would imagine that the bushing must be custom machined.
Does the large knob modification serve any particular purpose or offer any advantage over the factory model?
Thanks