Newbie question...


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Smokey Joe
December 5, 2012, 12:00 AM
Newbie question: I'm making a knife from OTS steel, de-tempered and flattened, by stock reduction using a common, electric-powered grinding wheel. The wheel's label says in clear English, "Do not grind on the side of the wheel."

My question is, what's the harm in that? Especially since I want to remove the stock flat, as with a file (but much faster) rather than in little concave lines, as with the perimeter of the grinding wheel. Got the holes drilled, in the full tang, for the pins for a slab handle. (The drilling, with a drill press, went great, btw.)

Confession: I've been trying it anyhow, regardless of the warning, and it seems to be working slick. The knife is beginning to take shape out of what was a flat bar of steel covered with gray oxide.
(I always wear glasses when doing this, btw, and have been holding the knife blank with a vicegrip plier so I have a nice big handle on it.)

The grinding is just like it was mild steel. Showers of sparks. I dip the blank in water every now & again to cool it.

So far, this has been an interesting experience. I've rehabbed a few knives; put a handle or 2 on a blank, but this is the first time I've taken a flat piece of steel, all myself, and "removed everything that doesn't look like a knife," to paraphrase Michelangelo.

Why doesn't the wheel maker want me to do something that works???

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Certaindeaf
December 5, 2012, 10:51 AM
Probably if you thin the wheel enough you'll wind up with a piece in your neck or something.

hso
December 5, 2012, 11:00 AM
Because it isn't safe.

The wheel isn't designed for the loading you're applying to it and the risk is fragmenting of the wheel and flying debris. It also damages the wheel since it isn't designed for the purpose and the structure ends up dished and uneven. This sets up wobbling in the wheel since it isn't radially symmetric any more and can damage the spindle or cause the wheel to come apart.

Also, the potential for having the item snatched out of your hand and thrown back at you is greater since there's no guard or bench for the item to strike. It is "annoying" to have a piece of steel thrown at you at close range at those speeds. It can result in hospital ER visits and expensive bills.

Smokey Joe
December 5, 2012, 11:09 AM
Well, that certainly was NOT what I wanted to learn, but thank you both of you for your quick responses.

I agree, Hso, it can be really annoying to be hit with a flying chunk of steel, or a piece of a shattered grinding wheel at high speed. Probably ruin my whole afternoon. ;-})

I'll try something else for sculpting that knife.

JohnnyOrygun
December 5, 2012, 03:02 PM
I worked in a structural steel and ornamental iron shop a few years ago as a project manager, we had a incident with one of the installers, he was grinding a weld in the field with a hand grinder, now I dont know all the details (I suspect he was grinding with the edge of the grinding wheel, but don't know for sure). Anyhow, what is important, is the wheel exploded, he was wearing safety glasses, but not a full shield. He had bits of the wheel embedded in his face and had to have several surgeries to get all the pieces out of his face. Even several years after the incident he was still having problems with extremely small bits the doctors couldn't get out, getting infected. I just relate this story to share what can happen, the guy who was hurt had been installing ornamental iron for the company for over 10 years and never had an incident. But when it happened, it was bad.
Be careful.
JohnnyOrygun

hso
December 5, 2012, 06:26 PM
There is a horizontal rotating platen that I've used in friends' shops that takes a disc on a steel platen. The RPMs are slow enough to keep from becoming a pen cushion if the work piece gets yanked away.

What a lot of makers use is a belt grinder with platen to flatten steel. A variable speed motor makes control that much easier.

Smokey Joe
December 6, 2012, 11:26 PM
("OK, it'll be safer, even if it takes 4x as long." he thinks) So: tonight, tried My little Harbor Fright 1x30 belt grinder, with an 80 grit belt. Voila! It cuts that soft steel FASTER than I was getting on the side of the grinding wheel! I never would have guessed. I get a veritable cloud of sparks.

Actually have to be MORE careful making the passes with the steel, on that belt, than I had to on the side of the wheel--Not that I wasn't careful there, believe me. That belt is agressive.

Downside: I can't get the grind quite as flat with the belt as I was getting on the side of the wheel. I guess I'm willing to live with that.

Probably would work even better, with a great big expensive variable speed 2x72 Bader, but I haven't got a GBEVS 2x72 Bader, and no liklihood of getting one in the forseeable future. And I do have the el cheapo 1x30 Harbor Fright.

I'll only used the outside edge of a grinding wheel as it was designed, from now on, when that application might get the job done.

So, thanks to all. I'll keep y'all posted.

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