Grinding Jig or Operator???

[Brian Kent]

I made this grinding jig for my 6" Delta grinder. I used the slower speed and dress the white grinding wheel.

The original little tool rest was too small and unsteady.

I grind a plane blade or chisel. I try to keep it steady and even. The hollow looks even. Then every time it turns out that the hollow is not as deep in the center. At worst, I have to hone all the way from front to back in the middle. This one is worse than most, but all of them are shallow in the center of the grind.

Do I need to scrap my jig and get the Veritas or is there some bad technique I am using.

There is a tiny bit of flex in the jig if I push hard front to back or side to side, but when I am grinding I use a light touch and cannot detect any right and left flex.

Thanks in advance for your collective wisdom.

Brian

[Paul Murphy]

Brian, if you dress the wheel with a flat face then any movement other than a perfect 90 will take extra material where it contacts nearer to the side of the wheel. I've read an article in FWW June '08 that advises a slight crown on the wheel, so that the middle of the wheel does most of the grinding and the crown keeps the ends of the blade from digging in due to flex/misalignment. Also the crown is supposed to protect the corners of the blade from excess heat.

I think your jig looks nice, it might work fine if you crown your wheel.

[Jim Koepke]

Paul's advise sounds good.

One way to determine if it is the equipment or the operator is repeatability.

If the operator is messing up, it would be difficult to do it the same every time. If you can get predictable repeatability, then it is likely the equipment.

jim

[Paul Saffold]

Paul, Thanks for your advice about crowning the grinder wheel.

I have been very careful to keep my wheel dressed square to the sides and flat. After all, we talk so much about keeping our sharpening stones perfectly flat. I mistakenly thought the same should apply to the grinder wheel.

I looked for the article and read it. Just as Joel described, I too have had trouble with corners of blades over heating. This is a real "eureka" moment for me.

Paul

[David Peterson]

Brian, you don't need to buy a Veritas - heck, you've just made one! And the Veritas wouldn't necessarily be an upgrade because it moves around a bit as well; not so much side to side as much as front to back. Like you, I have to maintain a light touch to avoid deflecting the Veritas jig, no matter how much it's tightened down. Not so long ago I was going to put it aside and make my own - something rock solid, infinitely adjustable and easy to reset ...hmmm.

Paul has already given you the way forward. Redress the wheel.

[Brian Kent]

That really helps. I'll see if it helps get a straight grind, but for sure it helps in not burning corners. It also lets me apply even pressure all the way across, without having to ease the pressure to lift the corner over the grinding stone.

I hollow ground my old Stanley #4 blade as a test and I'll hone it tonight because it's time to go to work. (It's hard enough to leave the shop and go to work when I like my job. It would be really tough if I hated my job).

One more shot of the jig, and the #4 blade after grinding, before honing.

[steve swantee]

Brian, I agree with David about the Veritas grinding jig-it does move no matter how much you tighten it down. I find I get a similar result as you are getting, so I wouldn't be in any hurry to chuck your tool rest. Might be worth it to try crowning the wheel and see if it helps.

Steve

[Brian Kent]

I should have said in the last post,

I tried crowning the grinding stone this morning and got good results so far.

I am really glad to hear that the most popular jig flexes, so I don't have to spend that money. Glad for me, not for you who have the jig and would rather it did not flex.

Brian