Not being a grinding expert, I would appreciate some advice from the grinding experts regarding proper wheels and techniques for grinding pilots on 3//32” HSS standard drills. We are grinding “pilot” points, 0.055” dia. x 0.22” length on standard .094 HSS drills. This pilot is non-cutting, and the shoulder is square, so no flutes or angles required.
We have done hundreds using the toolpost die-grinder as shown in the picture. The wheels used are 1”dia x .25 wide “smooth blue” aluminum oxide bits from McMaster.
This works reasonably well, but is sort of slow and prone to overheating the bit. These bits glaze somewhat, and are dressed every dozen bits.
In quest of doing this sort of thing more efficiently (and some other related prototyping tasks), I purchased a KO Lee B360 grinder for $300. It looked in fairly good shape from the photos, and all the pieces present. The shipper did not secure it properly, so it banged around on trucks, and arrived off the pallet, broken handles, chipped castings, crushed oiler rollers, shipped rack gear, etc. But wear on the ways was minimal, leadscrews and nuts good, and the heavy-duty spindle and motor sound very good. The maintenance folks had also packed the gearbox full of grease (likely due to a leaking shaft seal), so there were worn bushings and bearings. So after fixing the aforementioned, and installing new bearings and seals, repairing gear-shafts, etc. VFD, it’s up and running. (if anyone needs any $.02 on refurb of a similar grinder, I'm more familiar with the innards and repairs than I cared to be...)
I also motorized a spin-indexer as shown in order to have a compact way to grip those 3/32 bits, and other small parts.
To the question, what would be the best approach and wheels for grinding pilots on the 3/32 bits with the ‘new’ grinder. In a quick test, the Norton 32AA 80 K 7” diameter wheel shown seems to not work well with rotating the part and feeding the wheel directly vertical onto the bit. There appears to be chatter and gouging of the wheel versus a lot of grinding. I had the same issue trying to use white aluminum-oxide wheels on a Dumore toolpost grinder. The spin fixture currently runs at 20 rpm max (I can replace a motor/belts if necessary to vary the speed). I assume the hardness of those bits used on the die-grinder are significantly harder than the K wheel, which is why they work adequately with the die-grinder.
Thanks very much for any advice, pardon the long-winded post!
We have done hundreds using the toolpost die-grinder as shown in the picture. The wheels used are 1”dia x .25 wide “smooth blue” aluminum oxide bits from McMaster.
This works reasonably well, but is sort of slow and prone to overheating the bit. These bits glaze somewhat, and are dressed every dozen bits.
In quest of doing this sort of thing more efficiently (and some other related prototyping tasks), I purchased a KO Lee B360 grinder for $300. It looked in fairly good shape from the photos, and all the pieces present. The shipper did not secure it properly, so it banged around on trucks, and arrived off the pallet, broken handles, chipped castings, crushed oiler rollers, shipped rack gear, etc. But wear on the ways was minimal, leadscrews and nuts good, and the heavy-duty spindle and motor sound very good. The maintenance folks had also packed the gearbox full of grease (likely due to a leaking shaft seal), so there were worn bushings and bearings. So after fixing the aforementioned, and installing new bearings and seals, repairing gear-shafts, etc. VFD, it’s up and running. (if anyone needs any $.02 on refurb of a similar grinder, I'm more familiar with the innards and repairs than I cared to be...)
I also motorized a spin-indexer as shown in order to have a compact way to grip those 3/32 bits, and other small parts.
To the question, what would be the best approach and wheels for grinding pilots on the 3/32 bits with the ‘new’ grinder. In a quick test, the Norton 32AA 80 K 7” diameter wheel shown seems to not work well with rotating the part and feeding the wheel directly vertical onto the bit. There appears to be chatter and gouging of the wheel versus a lot of grinding. I had the same issue trying to use white aluminum-oxide wheels on a Dumore toolpost grinder. The spin fixture currently runs at 20 rpm max (I can replace a motor/belts if necessary to vary the speed). I assume the hardness of those bits used on the die-grinder are significantly harder than the K wheel, which is why they work adequately with the die-grinder.
Thanks very much for any advice, pardon the long-winded post!
