Fixing a bad grind. two questions

Awhile back I received a very generous gift from Vaughn, a pair of Benjamin's Best HSS bowl gouges. Over the years I've barely used them and up until very recently I've not had the proper set up to put the fingernail grind on them. Well I finally have most of the ducks in a row, my grinder, shop built wolverine clone (works for the most part... for now...) and a vari-grind tool holder from Oneway.

I've managed to royally mess up one of the gouges, to the point where I'm resigned to losing a fair amount of steel in order to fix things:


for now, ignore the Notch which is about 3/8" back from the bevel. I'm treating my error as a lesson in how not to do things. And hopefully I'll be able to fix that notch when I"m a bit more advanced.

OK

here are more pics of the current issue: I've managed to create a snaggletooth by focusing on the point of the gouge instead of doing a nice even sweep.



I attempted tonight to put something resembling the fingernail sweep back on, laying it way over on both sides, and then working it back and forth, spending less time in the middle.

I've got a white wheel and one of the original courser grit wheels on the grinder. The opposite side from this is beginning to look more like a typical elsworth or fingernail grind, my question is, should I simply keep on working on the finer grit wheel until I have both sides looking alike?

OR should I move over to the courser grit wheel to take more material off and get past the ugly point, and get the fingernail pattern established, Then switch over to the finer wheel for 'finishing'?

I realize I'm going to 'lose' a fair amount of steel in fixing this, so be it. I'd rather learn on this gouge than whichever one I buy to upgrade from it. (can you say Thompson? I thought you could...)

You definitely had the wrong angle.
How coarse is your coarse wheel? 80 grit is used a lot but, IMHO, is way to coarse and removes too much steel too fast.
Opinions, as they come in, will show a wide variance of reccomended grits. FWIW, I was taught by a professional master turner to use the 80 grit.
I now use 120 grit very happily. Methinks, just finding the right angle and regrinding with 120 will give you what you need.
Good luck. Let us know what happens.

Here is a link that might help you.
http://www.thompsonlathetools.com/sharpening.asp
I usually grind the slope with the flute facing the grinding wheel then set the Vari-grind like D Thompson shows in the download. He recommends 60° bevel and it seems to work pretty good .
John Lucas on YouTube has some good video on sharpening.

Frank Fusco said:

You definitely had the wrong angle.
How coarse is your coarse wheel? 80 grit is used a lot but, IMHO, is way to coarse and removes too much steel too fast.
Opinions, as they come in, will show a wide variance of reccomended grits. FWIW, I was taught by a professional master turner to use the 80 grit.
I now use 120 grit very happily. Methinks, just finding the right angle and regrinding with 120 will give you what you need.
Good luck. Let us know what happens.

Click to expand...

Frank,
not sure, I got this grinder as a freebie a few years back, put it into use just because I have it... it is only a 6" wheel. I picked up a 120 grit (white) wheel, and left the other as whatever was on there. I'll look at it later tonight when I get back home. I'd guess 80 grit or so would be about accurate. Definitely courser than the 120. As for taking material off, I may try it, I need to get 'past' that odd notch in the tip that I created, and that's a fair amount to remove.

Fred Belknap said:

Here is a link that might help you.
http://www.thompsonlathetools.com/sharpening.asp
I usually grind the slope with the flute facing the grinding wheel then set the Vari-grind like D Thompson shows in the download. He recommends 60° bevel and it seems to work pretty good .
John Lucas on YouTube has some good video on sharpening.

Click to expand...

Thanks Fred, Doug should know his stuff. I'm going to be picking up a couple of tools from him when I get some cash together.. (later winter or spring at this rate)

Ned Bulken said:

...I attempted tonight to put something resembling the fingernail sweep back on, laying it way over on both sides, and then working it back and forth, spending less time in the middle...

Click to expand...

At this point you should be spending all of your grinding time on the wings and none on the middle. Don't even let the middle touch the grinder for now. For every second you spend on the tip, you will need about 10 seconds on each wing. Maybe even more.

Ned Bulken said:

...my question is, should I simply keep on working on the finer grit wheel until I have both sides looking alike?

OR should I move over to the courser grit wheel to take more material off and get past the ugly point, and get the fingernail pattern established, Then switch over to the finer wheel for 'finishing'?

Click to expand...

Using the finer grit wheel will take longer, but afford you more control over how fast you remove metal. Using the coarser wheel will go faster, but with higher potential for you to mess it up again. It also looks like the gouge is getting pretty hot. I'd suggest lightening up on the pressure you're applying as you grind, if you can.

I'm assuming you are using the angle on your Vari-Grind that Doug Thompson shows on his site. How much of the gouge is protruding past the Vari-Grind? Also, how far from the wheel is your "Wolverine" arm (where the pointy end of the Vari-Grind goes)?

Vaughn McMillan said:

At this point you should be spending all of your grinding time on the wings and none on the middle. Don't even let the middle touch the grinder for now. For every second you spend on the tip, you will need about 10 seconds on each wing. Maybe even more.[/COLOR]

that's about the ratio I used last night.

Using the finer grit wheel will take longer, but afford you more control over how fast you remove metal. Using the coarser wheel will go faster, but with higher potential for you to mess it up again. It also looks like the gouge is getting pretty hot. I'd suggest lightening up on the pressure you're applying as you grind, if you can.

I'm assuming you are using the angle on your Vari-Grind that Doug Thompson shows on his site. How much of the gouge is protruding past the Vari-Grind? Also, how far from the wheel is your "Wolverine" arm (where the pointy end of the Vari-Grind goes)?

Click to expand...

just about 2" beyond the jig. And i built my jig to the 'elsworth' numbers 4" below and 7" out from the wheel for the 'pocket' the jig sits in.

Have you got an existing Gouge with an acceptable profile, or one you can borrow.

If so without the grinder rotating, set the gouge up in the jig, Angle, Protrusion, distance of pivot point from wheel etc. until you can follow its profile against the wheel, don't worry about the angles it's the profile you need to achieve and this can be done with all sorts of variations on the adjustments and actual contact position on the wheel surface which will be different for 6" and 8" wheels due to curvature etc.

Then as has been said work on the wings of you rogue gouge with those settings.



No jig will form the profile, it will only act as a pivot point for you to work with, you control how much metal is removed by how long you dwell in any area.

Chas Jones said:

Have you got an existing Gouge with an acceptable profile, or one you can borrow.

If so without the grinder rotating, set the gouge up in the jig, Angle, Protrusion, distance of pivot point from wheel etc. until you can follow its profile against the wheel, don't worry about the angles it's the profile you need to achieve and this can be done with all sorts of variations on the adjustments and actual contact position on the wheel surface which will be different for 6" and 8" wheels due to curvature etc.

Then as has been said work on the wings of you rogue gouge with those settings.



No jig will form the profile, it will only act as a pivot point for you to work with, you control how much metal is removed by how long you dwell in any area.

Click to expand...

I do have a similar gouge (thanks Vaughn!) which also has the swept back grind on it, and I've successfully kept that one going.. I just plain messed up with the one shown.

I worked on it awhile tonight... no pics as it isn't quite where I want it yet...

the snaggletooth is gone, as is the notch in the wing... I'm not happy with the sweep yet, but it is at least more even than it was, AND I learned a lot about how much/hard to grind... I used much lighter passes this time and it didn't get nearly as warm. I've got my turning club meeting tomorrow night, I'm going to take it with me and see if someone will take pity on me and throw it on a real wolvie and get me back in the game again.

Ned Bulken said:

...I've got my turning club meeting tomorrow night, I'm going to take it with me and see if someone will take pity on me and throw it on a real wolvie and get me back in the game again.

Click to expand...

Sounds like a good idea. Once you have the profile where you want it, you can use it to set you sharpening jig like Chas suggested.