Freehand grinding of Lathe bits

We have a diamond wheel in the shop where I sit (industrial fab etc.), and if you get caught grinding anything anything but carbide on it, you'll get summarily fired.

Cheers! Rich

I think it is a steel wheel with a small amount of diamond embedded in the surface. As opposed to a diamond grinding wheel that you would use on say carbide bits. You could not have much wear, like a CBN wheel and keep any degree of accuracy on the drill sharpening.

For a 6 inch wheel at 3450 rpm grinding dry, I would define rapidly as less than 5 minutes to noticeably reduce the cutting speed.

I do not grind tool bits everyday or even every week, but I think it is kind of like riding a bicycle. Not something that needs to be relearned after not doing it.

Dan

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In my years of grinding brazed carbide tools, I have inadvertently hit the wheel with steel, not having relieved the tool enough. Trust me, if you hit diamond with steel, the change is almost instantaneous. By the time you have surfaced one tool, the wheel behaves as if it's greased, so greater cutting pressure is required. It's really a good idea to avoid contact with steel unless the wheel runs at a temperature well under a red heat. Carbon burns at what, 1,100 degrees F? You'd certainly want to keep the temperature below that (at the point of contact).

Harold

I don't have the facilties to run a grinding wheel wet ,all my grinders are normal workshop bench mounted affairs . I pay only $23.00 for an 8 inch silicon carbide wheel so the cost is not much to worry about. I rarely use anything but HSS any way ,occasionaly carbide tips for harder materials.

Well that ruined any thought I had of buying a DD.

Thanks,

Wes

Why? The spare cost me $20, or ten cents a sharpening. I practice regrinding the chipped and broken ones freehand first, trying to leave the DD very little to clean up.

jsw

AFAIK I get much better mileage than that, but then, if there is much material to be removed, ie. a broken 3/8" bit, I will grind it freehand, also, once the cutting edge is ground, I quit rather than grind un till the whole end view is freshly ground. Gerry :-)} London, Canada

I saw a rusted old 57 Caddie that the owner painted orange and black with a roller and house paint. he drove it whenever his 67 Corvette was in the shop for bodywork, which was about half the time. He had me install a stereo system in it in the early '70s. Does that count?

Chuckle!

Now that's a discriminating car lover! Nothing quite like a nice orange and black rolled paint job to set off a nice car! Bet he painted the bumpers with aluminum paint, too, eh?

Harold

A hot, sunny day and rattle cans is the way to go, great, pebbled finnish! Gerry :-)} London, Canada

No. He still had some black house paint left...

BTW, it fit right in on Halloween. ;-)

Why go all the way to Finland for rattle cans? :)

drastically, and it

difference. I'd sweat

shop.

Question for you Harold. What can the HSM do to recover such a diamond wheel other than the white stick that comes with it? Got any tricks to reclaim? The first one I bought has been abused, not the second one......;>) I'd be nice to fix the first. phil kangas

pushed the ignore button. Gerry :-)} London, Canada

My only experience extends to the dressing stick, Phil. A lot depends on what they've done to the wheel. If it was run dry, and is heavily loaded, and dulled by having ground steel, but runs true, you may enjoy perfect success using the stick. What it does is attack the matrix, releasing the dull diamond and exposing new. The problem is, it shortens wheel life considerably, so you can't use it routinely. That's what's wrong with "clever" guys that think they know more than the folks that have done the research. I've never disputed that a diamond wheel will cut steel--but I know beyond doubt that it does so only briefly, and at considerable loss to the wheel.

If your wheel runs out of true, and has been badly abused that way, you may have some success mounting it such that you can rotate it slowly, with the back running dead true, then run a grinding wheel against the diamond wheel, barely making contact. Assuming it's a resinoid bonded wheel (the choice for brazed carbide, by the way), you may succeed in removing enough of the matrix to true the diamond wheel. Be careful, for some are only 1/16" thick when new, while others are 1/8". When you break through the matrix, what you have left is a piece of aluminum that is worth nothing more than scrap. I would use the grinding concept ONLY if the wheel is badly out of true.

Hope this helps, Phil.

Harold

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is badly out of

Thank you very much for your input, Harold! phil

OK, last dumb question, I swear.

Carbide inserts do not need grinding.

Brazed carbide bits cannot be ground with diamond.

Anything else can be ground with green wheels.

Why,. then, the need for diamond wheels?

Who told you brazed carbide can't be sharpened with diamond? Better yet, who suggested to you that green wheels are an acceptable compromise for a diamond wheel? I'd recommend you stay far away from that individual, for he surely doesn't know what the hell he's talking about. Mean time, NEVER use a silicon carbide wheel for grinding steel. That is just as stupid as using diamond for steel.

You are very best served to take advice from those of us that have actually worked with these grinders. I have, and have extensive experience in hand grinding lathe cutting tools. My advice will serve you perfectly well and keep you out of trouble. I can, and do, grind toolbits that work, and work as they are supposed to work. I am not lost on the subject of grinding toolbits, and have many years to my credit, and have authored several documents that are available for those that care to learn the art of grinding toolbits.

Sharpening brazed carbide toolbits is very best accomplished with a diamond wheel. In order to achieve the desired results, you must relieve the supporting steel substrate. That's not a big issue, and is easily accomplished by simply grinding a slightly greater relief angle that that which is ground on the carbide. Using the existing carbide as a guide, grind the steel beneath the cutting edge until the wheel is grinding on the carbide. You'd use an aluminum oxide wheel for this task, which is too soft to move much carbide, so it is more or less self gauging. You now have prepared the tool to be ground on a diamond wheel, which should be run wet, and supported by a table that can be set for the desired amount of relief. If, in the process of sharpening the carbide, you must remove enough to make contact with the supporting steel once again, regrind the steel with the aluminum oxide wheel. None of this is difficult.

A good idea is to have a wet diamond on one end of a double shaft motor, with an aluminum oxide wheel on the opposite end. That way you are properly setup to sharpen both brazed carbide and HSS with one grinder. I have operated in that manner since 1967 with excellent results.

Harold

Welcome!

:-)

Harold