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40/40 Grind Using the Oneway Varigrind Jig

Dennis J Gooding

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There has been considerable interest in using the Varigrind jig to duplicate (or approximate) the 40/40 grind produced by manual platform grinding. Several approaches have been proposed that either do not quite do the job or that require large values of gouge protrusion from the jig. I decided return to basics and see if I could get a better solution.

Some background first: There is a fairly well known iterative jig setting process that can be used to match the jig settings to any gouge that has been sharpened previously on a Varigrind jig. The process is as follows: Set the gouge protrusion to any reasonable value. (I use 1.75 inches, which is near the minimum that will provide clearance between the jig and the grinding wheel during the swing. Larger values work equally well but reduce the useable lifetime of the gouge.) Starting with the Varigrind pivot arm set to somewhere near mid range, repeat the following steps in sequence several times until a good match occurs at both the tip and the wings:

1. Adjust the sliding V-arm until the outer part of the gouge wing matches the grinding wheel. Lock the V-arm.

2. Adjust the jig pivot arm until the nose of the gouge matches the grinding wheel. Lock the pivot arm.

This process will converge to the desired setting in just a few iterations unless there comes a point where you reach the end of the adjustment range of one of the settings. The final settings can be confirmed by blackening the gouge tip with a marker pen and rotating the grinding wheel by hand while swinging the gouge. The bright spots produced will indicate what corrections are needed.

I decided to apply this technique to try to match my Varigrind jig settings to a gouge ground to a 40/40 grind. Specifically I would match the nose angle and the outer wing angle of the gouge. I cannot (yet) prove that the grind will exactly match the 40/40 grind between these limits, but the result will be a smooth transition from nose to wing.

In carrying out the above iteration, I almost immediately found that the pivot arm of the jig ran out of adjustment range. Specifically, the arm could not be closed enough to achieve the needed value. However, inspection showed that the circular slot along which the clamping bolt moves could be lengthened about a quarter inch or so, allowing the arm angle to close by another 10 degrees or so. This turned out to slightly more than enough to obtain the desired 40 degree angle at both the end of the wing and the nose. Lengthening the slot took only a few minutes using a round file.

The following pictures show the result that I obtained using my modified Varigrind jig to sharpen a half-inch parabolic-flute bowl gouge.

IMG_6224p.jpg IMG_6219p.jpg
 

Dennis J Gooding

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After posting this, I recalled that John Lucas previously posted what he referred to as his best approximation to the 40/40 grind using the Varigrind jig.
(John Lucas, Feb 20, 2019) Examination of his picture shows that the arm angle was fully closed. I guess that my contribution to the subject is the idea of lengthening the adjustment slot to allow the arm to close still further, thus allowing an exact match, rather than approximate match at both the wing and the nose.
 
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I have 3 gouges, I believe I'm going to experiment with this process on one of them. I'll be doing it with a Tru-Grind jig made by Woodcut.
Correct me if I'm wrong but I believe I read somewhere that this grind can only be done on gouges with V shaped and Parabolic flutes and can not be done on U shaped flutes
Thanks for posting.
 

Dennis J Gooding

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I have 3 gouges, I believe I'm going to experiment with this process on one of them. I'll be doing it with a Tru-Grind jig made by Woodcut.
Correct me if I'm wrong but I believe I read somewhere that this grind can only be done on gouges with V shaped and Parabolic flutes and can not be done on U shaped flutes
Thanks for posting.

Bruce I am not familiar with the tru-grind jig. Perhaps it has a wider adjustment range for the pivot arm and will work without any modification. If not, the results still may be satisfactory. I only have parabolic flutes and cannot comment on the U shaped flutes.
 
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Thanks for the thread. I'm getting back into the shop after a long hiatus. Will experiment with the VG with the extended slot.
 

Bill Boehme

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Thank you, Dennis, for the very informative thread. Using a variation of your technique, I may try to duplicate the 40/40 grind on the Tormek. But first I'll need to platform grind a gouge to the (hopefully) correct shape.
 

Dennis J Gooding

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Thank you, Dennis, for the very informative thread. Using a variation of your technique, I may try to duplicate the 40/40 grind on the Tormek. But first I'll need to platform grind a gouge to the (hopefully) correct shape.

Not at all Bill. No skill involved. Since we are fitting to only two points on the gouge grind, we do not have to reproduce the points between them. Using a platform, set it to produce the 40 degree nose bevel, and grind a small facet on the nose of the gouge, just enough to match the jig setting to. Then, at your leisure, position the gouge as it would be at the outer limit of manual grinding swing (the wing) and again grind a small facet. The facets should each extend all the way across the gouge.
 
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Thank you, Dennis, for the very informative thread. Using a variation of your technique, I may try to duplicate the 40/40 grind on the Tormek. But first I'll need to platform grind a gouge to the (hopefully) correct shape.

Already done Bill. Using the TTS-100, bar set to “A” position, 75mm protrusion, SV-186 position 3. I use a Grizzly wet unit but all the settings are the same. Here are pics of my Crown Razor 1/2” (5/8” shaft) bowl gouge (parabolic flute) with 40/40 grind using above settings.

Edit: rechecked my settings. The “JS” setting is 2 not 3.
 

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Hmm, not having used the varigrind or other jigs other then the Ellsworth, I really don't understand what is going on here. A video would really help me... There was a thread a while back on the main forum about a Ron Brown (not sure it that is the correct first name...) jig and set up, but he used a 3 inch protrusion to get a very close imitation of the 40/40 grind. The more I use that grind, the more I like it....

robo hippy
 

Bill Boehme

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Already done Bill. Using the TTS-100, bar set to “A” position, 75mm protrusion, SV-186 position 3. I use a Grizzly wet unit but all the settings are the same. Here are pics of my Crown Razor 1/2” (5/8” shaft) bowl gouge (parabolic flute) with 40/40 grind using above settings.

Edit: rechecked my settings. The “JS” setting is 2 not 3.

Thank you for the information, Doug.
 
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Bill, I use a Tormek BGM-100 tool bar mount for an 8” slow grinder to shape my gouges, using the SVD-186. I use it to grind heel relief angles as well, as shown in the posted pics.
 

Dennis J Gooding

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Hmm, not having used the varigrind or other jigs other then the Ellsworth, I really don't understand what is going on here. A video would really help me... There was a thread a while back on the main forum about a Ron Brown (not sure it that is the correct first name...) jig and set up, but he used a 3 inch protrusion to get a very close imitation of the 40/40 grind. The more I use that grind, the more I like it....

robo hippy

Reed, I seem to have misplaced my directors beret so I won't be making a video. (Besides, I don't Know how to.) I tried out the Ron Brown approach and it seems to give about the same results as mine at the expense of losing another 1.25 inches of gouge life compared to my approach.
 
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So, is the difference mainly in the vertical arm angle? Looks like it is far more vertical than 'normal' for the 40 degree bevel setting. Since I learned the 40/40 grind, I never use a swept back gouge any more.

robo hippy
 
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With all the snow today I was able to get some time to try and replicate the much recommended 40/40 grind.
I accomplished it with the Tru-Grind jig set on the #1 setting and the protrusion was at 1,7/8"
This took some back and forth for me as far as getting the side grind to match the toe grind at the desired angle so I had to experiment with the protrusion a little bit before I found the correct length.
Actually, as Dennis stated, there was some back and forth with the sliding arm along with the jig angle itself. The jig angle was the first thing I set though and once I got a perfect 40* on that with the front toe I didn't change that again, it was more trying to get the side angle to match the toe angle by using the protrusion vs the sliding arm distance.
That put me at exactly, according to one of those steel protractors, At 40* from bottom of flute to toe bevel and 40* from side of flute to side of bevel.
I didn't try any cuts with it today because with all the snow and shoveling that goes with it I decided to crack a few tops of adult beverages AFTER I was done with the grinder.
 

Bill Boehme

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... I decided to crack a few tops of adult beverages AFTER I was done with the grinder.

A very wise and well earned decision from all perspectives.

You have my deepest sympathy for the rotten weather you're going through. I guess that I won't mentioned that I spent the day outdoors enjoying the clear sunny weather and mild temperature.
 
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Going to the shop and try to finish a bowl I started. Need to turn a jam chuck first. Looked at a couple of videos and a book. Reversed the half log to start with the bark toward the tailstock. Will take time to review this thread and t he modifications to the Vari-Grind. Takes on a new meaning of- Back to the old grind!
Born and raised up North. Ohio, Queens, NY and KY (way out in the country), snow and cold weather never bothered me. I always thought if snow was such a bother, no one would live north of Knoxville, TN.
 
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Don is one of the most respected authorities on sharpening.
Tom, can you provide a specific url. I just can’t find the 40/40 instructions within the Evolution system.
Okay, I don't understand why, but if you look at the url for geigersolutions home page https://www.geigerssolutions.com/, the second photo in the list shows the adapter for the 40/40 grind. I contacted Don via email and ordered it.
 
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Okay, I don't understand why, but if you look at the url for geigersolutions home page https://www.geigerssolutions.com/, the second photo in the list shows the adapter for the 40/40 grind. I contacted Don via email and ordered it.
Thanks Tom. I just didn’t see anything(instructions) regarding the wings and the interface shape connecting the tip of the gouge. Let us know how you do.
 
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