Help me save my bowl gouge - Woodworking Talk - Woodworkers Forum
 
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post #1 of 11 Old 06-21-2014, 03:32 PM Thread Starter
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Help me save my bowl gouge

I'm a bowl turning newbie. Just took a class at Woodcraft. It's awesome.

Here's the setup: I have typical starter set of lathe tools... the Benjamin's Best setup. It came with a bowl gouge. I tried to sharpen it with my wolverine / varigrind jig. I screwed it up. Big time.

I tried to rescue it using the settings found on this PDF.

http://www.carlford.info/pages/jigs_..._Templates.pdf

I seem to be doings something wrong. Below are the pictures I took of my abused tool.

Any suggestions on how to fix my mistakes would be greatly appreciated. Keep in mind that if this is too far gone I can get another just like it for less than 20 bucks. Or I can get a Woodriver or something for in the mid fifties.

Thanks in advance!

Oh, and it looks rusty because I was dipping it in water to cool it and I guess I didn't dry it very well.




Last edited by MidKnight; 06-21-2014 at 03:38 PM.
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post #2 of 11 Old 06-21-2014, 04:04 PM
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ok after a close look it is off but not terrible bad
just looks like you need to follow those directions and grind it more on the wings near the center !!
hope that makes sense

Last edited by robert421960; 06-21-2014 at 04:08 PM.
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post #3 of 11 Old 06-21-2014, 05:22 PM
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I can't see how you have the Vari-Grind set, but from the look of things, I would set it to approximate the shape of a swept back Ellsworth grind. Also the nose angle seems to be a bit too pointy for a beginner. I would go for a more blunt angle of about 60.

You can recover from the situation, but it is a bit difficult to explain in words. It would be better to see a video. Nevertheless, I will make an attempt. First, you need to turn the tool over so that the flute is pointed down and then grind the basic profile as in the illustration below.

Name:  bowl-gouge.jpg
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The dotted line represents the misshapen grind that is currently on the tool and the desired shape is below it. I am showing a 60 nose angle and swept back wings that are like many turners put on their bowl gouges.

When you turn the tool over and place the cutting edge against the stone, the object is to grind an approximately straight line (or slightly convex) from the nose to about 3/4 inch back. When you do this, there will no longer be a sharp edge -- it will be a big flat area on each wing. But, don't despair ... yet anyway.

The next step is to put the gouge in the Vari-Grind jig and very carefully grind away steel until the flat is gone all along the edge. Important: do not grind away any more steel than necessary to get a sharp edge all along the tool. Some areas will require more grinding and some areas will require hardly any grinding. A very important thing to know about jigs is that they only set the grinding angle and it is totally up to you to determine the shape.

I don't know if this helps -- it is always easier to see how it is done.

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post #4 of 11 Old 06-21-2014, 05:33 PM
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Paint the entire bevel with black felt marker so you'll know in an instant where the metal is coming off. Do that as often as needed.

I tune up a set (10?) of big Sorby for a turner down the street in return for lathe time.
My General Tools angle gauge says the bowl gouge is 60 degrees.
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post #5 of 11 Old 06-21-2014, 05:35 PM
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Looks to me as though you had the Wolverine jig arm extended too far out from the grinding wheel. If you bring that pocket in closer, the gouge will ride up the wheel from where it currently sits and you'll see the heel of the bevel becomes the only contact point (until you grind it away some.)

It's really easy to grind away the tip of the gouge. I always start grinding with the handle way over to one side, the cheek of the bevel resting against the spinning grindstone, and rotate the handle up to the center. As soon as it reaches the nose, lean it back (so it breaks contact). Then swing the handle over to the other side, rest the cheek onto the wheel, and swing it to center again.

(There's a lot more metal in contact with the wheel when you're on the side cheeks, meaning if you rest there a little longer than you intended to there's not much damage done.)

I was told (by Ernie Conover) not to quench high speed steel, it really does not need it.

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post #6 of 11 Old 06-21-2014, 06:25 PM
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Looks way to blunt to me. I use the Sorby but all grinding jigs work almost the same (I have used a Wolverine).
Here is a great, and short, video on how to correct most grinding problems. It does start with the bowl gouge.

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post #7 of 11 Old 06-21-2014, 06:31 PM
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This is a video by Doug Thompson on sharpening tools. I found this very helpful.


He also has a template on his site that you can print to set the angle of the leg of the varigrind jig.

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post #8 of 11 Old 06-21-2014, 06:40 PM
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If the tool is getting hot then you must be doing something very wrong. It should barely get warm when sharpening. Are you using a white aluminum oxide grinding wheel? If you are using a gray silicon carbide gray wheel, toss it and get an aluminum oxide wheel.

When sharpening, you need to be using a feather light touch. Very gently touch the tool to the wheel. An aluminum oxide cuts the steel very fast and with very little heat. A silicon carbide wheel cuts slowly and gets the steel red hot.

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post #9 of 11 Old 06-21-2014, 08:35 PM
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I made the video below just because people have the same problem you have. If you look at the link to Doug Thompsons gouges it shows the set up he uses and the way the gouge should look. Then look at my video to learn how to correct bad grinds. Then just try to make your gouge look like the photo or drawing of Dougs bowl gouge.
You only need to use a light touch but if your grinding for a long time the gouge will get hot. Use water too cool it frequently so it never really gets that hot and you will be OK no matter what wheel you grind with.
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post #10 of 11 Old 06-21-2014, 09:51 PM
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One added piece of info: Three are two wings and only one tip work the wings and get them to show no glare on the edge any glare on the edge you are not ground down far enough in that area. Then work the tip and blend it to the wings, reason for this if you were to grind the tip with each pass from wing to wing you grind to much away from the tip.

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post #11 of 11 Old 06-22-2014, 06:59 AM
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Ditto YOu only need to grind where you need to remove metal to get the shape you want. Most people think that using a jig like the wolverine requires a simple grind from one side to the other and your done.
If the edge and shape is perfect already this works. However while you are swinging the jig it's very easy to put too much pressure on one area or another. This leads to a dip in this area and maybe a rise or hill in another area. After a few grindings the edge looks more like waves on the ocean instead of a nice smooth arc.
What you have to do is to grind longer in areas where the edge is too high, and not grind at all where the edge is too low.
If you look at the nose of a bowl gouge from above most of the grinding problems I see are about 11 oclock and 1 oclock. You get a dip in the edge by grinding either slower or more forcefully in this area. Quite often it's the whole nose from 11 to 1 that is too low so you have to grind more on the wings and not any on the nose to correct the problem. That's the problem the gouge in the photo shows.
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