Bowl gouge sharpening issue

[Gary Pennington]

I'm sharpening on a 600 grit CBN with a Wolverine vari-grind jig and use a jig to set the stick out from the vari-grind at 1 3/4", Doug Thompson's recommendation. I also have a shop made jig to set the Wolverine base at the same distance from the wheel every time. The issue is that sometimes when I start to sharpen the grinder hits the top or cutting edge on one side and the bottom or heel of the gouge on the other. It takes a fair amount of grinding to even out and puts more of my tools on the floor than I think is necessary. I think I do everything the same every time but this inconsistency is bugging me. Here's a pic that I hope shows the issue. Hoping someone can shed some light on this.

Thanks! Gary

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[Dave Mount]

Hey Gary -- I set up using the same equipment the same way and don't have this problem, so something must not be as it seems. If I understand you right, it's not just that at one sharpening you're back on the heel and another on the tip, but that it's asymmetrical, that you're on the heel on one side and on the edge on the other. That makes me think the inconsistency is in the rotation of the gouge in the vari-grind. The vari-grind needs to register on both sides of the flute evenly -- if it rolls one way or the other you'd get what you report. By any chance is this a gouge that is well worn? I ask because I had a 1/2" Thompson bowl gouge that I used so much the flat on the vari-grind was creeping off the end of the flute. I had to grind a flat back onto the round shaft to give the vari-grind something to register to.

Here's that gouge from the top and from the side showing the additional grinding:

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Just a thought,

Dave

[Gary Pennington]

Thanks Dave,
No the gouge isn't worn, at least that I can tell. The vari-grind is maybe 3 years old and I'm a hobby turner so it hasn't had a lot of wear & tear. I agree that the gouge doesn't register consistently radially but there really isn't much to go wrong. The gouge still has plenty of flute for the screw clamp to mate to.

Gary

[Thomas Wilson80]

Gary, Not sure what’s going on but I often will color the bevel on the tool tip with a colored marker then put it in the varigrind and then while holding the tool in the jig against the wheel, rotate the wheel by hand to make sure it is in the right place. If the distance is correct, then an even strip of steel where the wheel grinds away the marker is produced. But this may not help if you are getting inconsistent grinding of the tip and heel simultaneously…

tom

[John K Jordan]

I'm sharpening on a 600 grit CBN with a Wolverine vari-grind jig and use a jig to set the stick out from the vari-grind at 1 3/4", Doug Thompson's recommendation. I also have a shop made jig to set the Wolverine base at the same distance from the wheel every time. The issue is that sometimes when I start to sharpen the grinder hits the top or cutting edge on one side and the bottom or heel of the gouge on the other. It takes a fair amount of grinding to even out and puts more of my tools on the floor than I think is necessary. I think I do everything the same every time but this inconsistency is bugging me. Here's a pic that I hope shows the issue. Hoping someone can shed some light on this.

Thanks! Gary

475294


I've never seen that problem. Hard to tell from one photo. Maybe take some photos of the gouge mounted in the jig and the sharpening in progress. Also, is wolverine mounted precisely parallel to the side of the wheel?

Just curious, I hope you are using the orig Varigrind and not the Varigrind 2. I have both and I only keep the 2 to let people try it and tell them why I don't like it. But neither one should produce the asymmetrical grind you describe unless the gouge is not mounted properly in the jig. Pressure from the bolt head (or plastic pressure plate on the "2") must press evenly and equally on both sides of the flute. If the gouge is rotated in the jig something is wrong. Are you trying to sharpen a gouge too big or too small for the jig?

Also, it might not make any difference but a photo of the how angle of the jig is set might help. I assume you set it once and never change it.

Are you a member of a local club or have friends that are adept at sharpening? It might work wonders for two to share sharpening techniques. Another pair of eyes on how you are setting up and sharpening could solve the problem.

BTW, I love Doug Thompson and have known him for a long time. At last count I had over 50 of his tools in my shop. But I am not a fan of ANY of the grinds he puts on his tools. I reshape them all, gouges, skews, scrapers, whatever. (If you didn't know, he also sells round rods of different diameters, perfect for grinding special tools. I've ground some into small NRS with various profiles.)

[Reed Gray]

Well, I only use a platform for sharpening. I have seen several variations of a 'stop block' used to set the arm distance on the wolverine jigs so that extension is exactly the same every single time. A stick, marks on the arm. piece of angle iron/aluminum, etc. Having it perfect repeat so you don't have to guess and just get it close helps.

robo hippy

[Prashun Patel]

Is your v arm centered to your wheel?

Is it happening on all gouges you've tried?

[Richard Coers]

Do you put any pressure on the gouge or do you let the grinder do the work? It's nearly impossible to apply equal pressure as you move the gouge. Let the grinder do the work. Second problem is moving faster on one side than the other. I grind one side, then the other side, and then blend the nose.

[Gary Pennington]

Checking the Wolverine base I found an issue--it was slightly loose and could move side to side +/- a 1/16 or so. When I retorqued the mounting screws it pulled the base off the center line about 1/16", there must have been a chip or something under it when I put it together. I'll take it apart today and remount the base, then retry grinding.

To answer a couple of questions>

It's the vari-grind 2--John, Why don't you like it?

I use a stick cut to length to set the distance from the basket to the wheel
I use Doug Thompson's recommendations on vari grind setup and grind. I don't have enough experience to experiment with other grinds--I'm not sure I could tell the difference.
I grind with minimum pressure, just enough to hold the tool on the wheel. Starting with the tool handle far to the right, then swinging around to the left hoping to grind in one sweep. That rarely happens.

Thanks for pointing me to the issue, I've been dealing with this for months.

Gary

[John K Jordan]

I'm glad you found the problem and the easy fix.

The Varigrind2 is great for preventing you from accidentally letting the gouge slip off the sides of the wheel, perhaps due to inattention or maybe staying up too late. I never understood the need for this since I have not yet let a gouge go off the edge off a wheel edge with the original Varigrind jig. It appears to me the V2 constrains the sharpening to the the center of the wheel and a little to the left or right if grinding wings. Since even CBN wheels wear with use, it seems to me the center of the wheel will be worn down quicker. With the original Varigrind I spread the wear over the surface.

FWIW, I sharpen my many spindle gouges on the Tormek with a 1200 grit wheel. If I want to reshape a spindle gouge I use the Tormek jig on a fixture I made years ago to use a 600 or coarser grit on a bench grinder.

I use the Varigrind to sharpen some bowl gouges.

I use a flat Wolverine platform to sharpen almost everything else by hand on a 600 grit CBN wheel: spindle roughing gouges, skew chisels, scrapers, negative rake scrapers, all hand scrapers, and special custom tools. I also sharpen some bowl gouges by hand on that wheel using the flat platform. It's quicker than setting up a varigrind and very effective (with a little practice). Also, I remove all grinding burrs with the leather honing wheels on a Tormek.

BTW, the Wolverine comes with a big platform but I bought some of these mini platforms which I prefer for most tools:

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Also, to set the platform angle I make setting aids from plexiglas. The first picture shows some but since then I've started painting one side white to make them easier too see. The second picture of one setting the platform to 90-deg to grind hand scrapers.

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My sharpening station has evolved over the years but here's a picture from a few years ago and the Tormek adapter (I no longer use CBN wheels with radiused edges - they don't make sense except for one special case.)

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This page stolen from the Tormek manual illustrates some of the variation in grinds you can get by changing the two angles. Perhaps the Varigrind has a similar table. The principle would be the same but the numbers given for the Tormek may be different. FWIW, I don't remember the history but this method of putting a useful edge on a gouge has been around a long time, probably long before the Oneway and Tormek jigs - lots of people have devised fixed and adjustable jigs for the grinds they want. The different grinds can be quite useful in some situations.

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Checking the Wolverine base I found an issue--it was slightly loose and could move side to side +/- a 1/16 or so. When I retorqued the mounting screws it pulled the base off the center line about 1/16", there must have been a chip or something under it when I put it together. I'll take it apart today and remount the base, then retry grinding.

To answer a couple of questions>

It's the vari-grind 2--John, Why don't you like it?

I use a stick cut to length to set the distance from the basket to the wheel
I use Doug Thompson's recommendations on vari grind setup and grind. I don't have enough experience to experiment with other grinds--I'm not sure I could tell the difference.
I grind with minimum pressure, just enough to hold the tool on the wheel. Starting with the tool handle far to the right, then swinging around to the left hoping to grind in one sweep. That rarely happens.

Thanks for pointing me to the issue, I've been dealing with this for months.

Gary

[Dave Bunge]

Also, to set the platform angle I make setting aids from plexiglass.
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John, how do you make the plexiglass setting jigs?

I guess the process is something like this:
1. Set the platform to the desired angle
2. Place a piece of plexiglass on the platform and extend it past the wheel.
3. Trace the outline of the wheel on the plexiglass.
4. Cut the plexiglass along the line (How? Scroll saw with fine blade? After cutting, do you grind away some of the plexiglass with the wheel to fine tune the match (seems this could be helpful, but might clog up the wheel)?)
5. Spray paint the jig to improve visibility.

I'm interested to hear any details or tips you can share.

Thanks,
Dave

[Dave Mount]

BTW, I love Doug Thompson and have known him for a long time. At last count I had over 50 of his tools in my shop. But I am not a fan of ANY of the grinds he puts on his tools. I reshape them all, gouges, skews, scrapers, whatever.

Hey John--

At the risk of hijacking the thread, I'm curious what aspect(s) you don't like about Doug's bowl gouge grind -- nose angle, length of wings, or degree of "roll back" on the wings (set by vari-grind protrusion)? Not defending the factory grind, just curious.

I've actually not found the nose angle to be consistent from bowl gouge to bowl gouge as they come from the factory, though in my hands they get ground to whichever set-up jig I sharpen them with. I do use his protrusion on the vari-grind though. That's one sharpening variable I've not done much experimenting with.

Best,

Dave