New grinding wheels for HSS and tool steel grinding

I have an old Black and Decker 6" grinder that has served semi-OK for
my pretty modest tool grinding needs. It has the standard grey wheels
which I know aren't the best for tool grinding.
I want to get better at tool grinding (nowhere to go but up) and am
going to get a new pair of grinding wheels. I will be grinding HSS
toolbits and want to try making some modest tools with oil hardening
drill rod and tool steel. These tools will be mostly 1/4" square and
round and perhaps eventually just a little bigger up to perhaps 3/8".
(I probably need a larger grinder but the budget is tight right now).
I've done a lot of reading of the newsgroup archives and on the net
and it appears that aluminum oxide wheels (white) are probably best
for my application, in perhaps a 46 grit and a 60 grit
Any opinions would be gratefully accepted by this relative newbie.
jim
Reply to
Jim in VA
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You're on the right track, but you may find your options limited by the wheel you're stuck with. When you see the opportunity, you might consider building a grinder from a 3600 RPM motor with shafts out each end. You'd make a couple of adapters that permit mounting grinding wheels with a 1-1/4" bore, which is the most common of all wheels, due to their use on small surface grinders and cutter grinders. Wheels are available in the broadest selection in that configuration, in both 7" and 8" diameter wheels, with a wide range of widths, and they typically can be driven that fast. My personal choice is to use 1/2" wide wheels, which, again, are the most common.
For your grinder, I'd suggest either a 32A or 38A wheel (Norton) or equivalent. Stick with a vitrified bond, and shoot for a hardness about J for the 46 grit wheel, and maybe slightly harder for the 60 grit wheel, a K or an L. That way you can rough your tools quickly and then finish them without losing the form, or corner of the wheel, as rapidly. The wheel might be marked something like 38A60L8VBE.
Learn to dress your wheels properly, too. That's more important than anything. A dull wheel burns like crazy and cuts very slowly. I suggest the combination of a mounted diamond, or diamond cluster, and a dressing stick. Diamond dressed wheels tend to cut way too hot for offhand grinding, so bring the wheel true with a diamond, then rough the surface slightly with a dressing stick. Makes for faster and cooler grinding.
Harold
Reply to
Harold and Susan Vordos
Get a Norton SG wheel in the proper hardness and you will never want anything else. They are more expensive, but will out perform any conventional alox wheel. They easily last twice as long between dressings.
See
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comparative data.
Randy
Reply to
R. O'Brian
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Thanks, Harold. That is a _lot_ of help.
jim
Reply to
Jim in VA
I would look at the Norton SG or equivelient type grinding wheels. The Blue wheels last longer and keep their form better. The main thing is to keep the wheels sharp and clean. Use a diamond dresser and a good tool rest. Take a look at this one from Lee valley tools. It is very adjustable and with the slot in the rest you can clamp a dresser to the guide and get a very nice smooth wheel.
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your old grinder is still in good shape then just get the new wheels, but if the bearings are going you may want a new grinder or maybe replace the bearings to bring it up to snuff.
Jim > I have an old Black and Decker 6" grinder that has served semi-OK for
Reply to
machineman
If your grinding needs are modest, Jim, you shouldn't have to get too fussy about it. Ordinary M2 hss and similar grades are not terribly hard to grind, unless you have a lot of material to remove or you're concerned about productivity. And they can take a lot of heat. Remember, they're tempered at around 1,000 deg. F, so you don't have to worry about "burning" them if they turn a little brown or blue. The thing is to keep them from getting *bright* red right on the surface you're grinding. Very dull red is tolerable. (DON'T dip hss in water to cool it between passes. You'll be inviting microcracks if you do, and a tool could fail on you at an unpleasant time. High-speed steel can take the heat.)
The white wheels will grind cooler, but I'm with machineman on this one. I've used both Norton white wheels and ordinary gray wheels on M2 and equivalent, and I'd use either for home-shop use. If you want to go for the slightly better choice, go for white. IMO, it's more important that the wheel be *coarse* for rough grinding and shaping, than that it's premium-white or gray. Coarse wheels run much cooler and cut faster.
-- Ed Huntress
Reply to
Ed Huntress

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