Difference in grinders????

[Jerry Marcantel]

I purchased a Thompson 1/2" V bowl gouge not too long ago. My grinder is an 1800 RPM 6" Baldor, and I set up a jig to sharpen my stuff at 60° nose bevel, with swept back wings ranging from 9/16" - 13/16", depending on the od of the gouge. Before I sharpened DT's bowl gouge, I checked the sweep, which was 7/16" - 1/2", and the nose, which was 60°. After the first try at sharpening DT's with my jig, the nose stayed at 60°, but the wings changed quite a bit in lenght and angle. I didn't think to check the side angle before sharpening, so I can't say what it was when I recieved it, but now it's at 10°, and the wings are almost 3/4"" long..
Another problem I'm having is the wings turn blue real fast compared to the other gouges that I have and made. I think I'm fairly proficient in grinding tools, but this has me flustered...... And that's on a reasonably slow speed grinder.
I have an 8" grinder also, but it runs at 3800 RPM.
I also purchased a Wolverine jig, so now I don't really know which grinder to set it up under..... Any tips and thoughts would be appreciated......... Jerry (in Tucson)

[Mark Levitski]

I've never understood the statements I've read about the Wolverine Vari-grind nose angles being set with the v-pocket slider. I start my set-up with the wing angles. The only way to adjust the wing angles is by moving the v-pocket part of the jig in or out. The nose angles can be set by either the v-pocket or the jig's leg, but first I set the v-pocket to where I want it for the wing angles. Then I can adjust the leg for the nose.

With the handle of the gouge parallel to the face of the grinding wheel, the side of the shaft of the gouge is presented to the wheel to be ground. It is this side that forms the wing bevel. Moving the v-pocket in or out results in a change in the angle of that wing bevel.

There are several variables to factor in to grind a gouge on this jig. When, after fooling around and experimenting, you find what you want in a grind, make notes and somehow make it repeatable. Sometimes this is the only way to learn how to make the best use of it.

Turning the steel blue on today's high-end metals for our turning tools does not necessarily mean that you ruined the edge. Doug T. can chime in on that since i'm not an expert.

[Jim Burr]

I think Doug sharpens on a 8" wheel as opposed to a 6". Double check.

[Bernie Weishapl]

Yep I called Doug on my first gouges a year or so ago and he uses 8" wheels.

[Doug Thompson]

Jerry,
Go to my website and download the sharpening guide, place your vari-grind on that picture and set the leg angle... this will never move again. The leg angle sets the wing angle on a bowl gouge and spindle gouges don't have wings so there is no reason to move the leg. Use the V arm to set the nose angle to 60 degrees and grind away. Burning to a purple color won't hurt the steel but dressing the wheel and lighter pressure takes care of it. A wild guess without any more questions would be that the leg on the Vari-grind was set different than the picture.

Mark uses a different way to set the Wolverine that works just fine but requires two adjustments, I remove the one adjustment to keep it simple.

[Doug Thompson]

I missed the question about the 6 or 8 inch grinders. I grind the tools on a 8 inch grinder and suggest a slow speed because it takes longer to get in trouble. It doesn't matter 6 or 8 inch but Oneway asks for a spindle height which require some smaller grinders to be raised.

[Harry Robinette]

First the nose extension from the tip to the var-grind is your protrusion 1 3/4 or 2" or what ever you decide to use.The in and out of the V-arm sets the nose angle. The leg on the vari-grind sets the angle on the side wing the further forward the leg the straighter the angle,back with the leg the more the wing rolls inward.An 8" grinder is recommended because of the amount of hollow grind in the gouge.
Jerry-Not knowing what jig your using it's hard to tell you any thing.But using the Wolverine just set the protrusion to what you think you'll need, I use the size of the V bucket. Then set the nose to the angle you want 60* say,then move the leg forward and backward to get the wings angle were you want them.USUALLY this works but sometimes you need to adjust the V-arm in and out a couple of degree,you should be able to get thinks worked out if you use this system. Hope this helps.

[Jerry Marcantel]

I missed the question about the 6 or 8 inch grinders. I grind the tools on a 8 inch grinder and suggest a slow speed because it takes longer to get in trouble. It doesn't matter 6 or 8 inch but Oneway asks for a spindle height which require some smaller grinders to be raised.

I would rather use my 6" grinder because it's slower than my 8". Also, a couple years ago, I lucked into a deal on 6" grinder wheels. Got 1040 - 6" and just 40 - 8" wheels for a hundred bucks. I could have gotten more, but my poor truck was sagging with all the abuse I expose it to.. Took 2 trips... Thanks for the tips, guys...... Jerry (in Tucson)

[Michael James]

Jerry, the other thing I don't think was mentioned in this thread is that Doug uses 1 angle on the vari-grind. So your 60* or whatever is determined by the distance from the wheel (and as mentioned a specific vertical relationship to center on your arbor) and then the wings will always be consistent. I've started using that, in addition to the Ellsworth jig and setup for a 5/8 gouge. Your problem lies in there somehwere. You can download Doug's setup suggestion - full size sheet on his website, no obligation and you might be able to "template" your jig to that angle.
Best of luck amigo,
mj in nm

[skott nielsen]

So what happens if I use Dougs template for leg angle but set the nose for 45 degrees? Does this make a usable grind for a bowl gouge?

Skott

[Doug Thompson]

Skott,
I'll grind a tool to 40-45 degrees then take a picture, late tonight I'll post it.

[skott nielsen]

Wow, thanks doug, Looking fw to it. I am hoping to get the advantage Batty and Mahoney advocate with the reliability and precision of a jig.

Skott

[Doug Thompson]

Below is a picture of when the nose angles change without changing the Vari-grind, watch the wings get thinner as the angle changes. The leg angle and nose angle are in direct relationship to each other, I give a leg angle that works well with a 60 degree nose angle, at a 50 degree nose angle the wings get narrow and at 40 degrees the grind is unusable.

The Johannes Michelsen freehand grind is in the picture to show the difference... we talk grinds and IMO this is the best on the market.


grinds nose angles side smaller.jpg

Side grind picture from the top
1. Johannes Michelsen's 45 degree freehand grind
2. My standard 60 degree grind using the Vari-grind
3. 50 degree grind with same Vari-grind leg angle
4. 40 degree grind with same Vari-grind leg angle



grinds nose angles top smaller.jpg

40, 50, 60 degree nose angle and the Michelsen grind.

Top grind picture shows how the wings get thinner and tinner as the nose angle changes. Note how the 60 degree nose and the Michelsen 45 degree are the only usable grinds in the picture.

The answer is a leg angle is set for one nose angle give or take 5 degrees. That's why freehand grinds are so important to learn.

[skott nielsen]

Very helpful. I have been trying to grind my Thompson tools with a 45 degree nose using the raptor set up and 23 degree leg angle and getting a tool that works nicE outside a bowl but poorly inside! Now I am understanding why!

[Fred Perreault]

Great pics Doug. To some, sharpening their own tools seems frightening, but it is not nuclear physics. A basic understanding and practice will make perfect. Of course, some good tools to allow repeatability coupled with pics and video will go a long way. Thanks