Smaller Wheels That Fit 6" Grinder Arbors?

[SteveHGraham]

I was thinking it might be nice to get a bench grinder with very small wheels, like 3-4". I could use it for putting hollow grinds on small edged tools. I looked up small bench grinders, and they are apparently so weak they're not worth buying.

It occurred to me that I could solve the problem by buying a 6" grinder and putting smaller wheels on it.

Before I spend the evening searching the web, can anyone tell me whether there are small wheels out there that will fit a 6" grinder's arbors?

[spro]

If you put smaller wheels on that grinder as it is, you may run out room. The motor head is so large that well, I, you can't quite swing the tool you are grinding. I believe that you had buffer polishing type units. Those had longer supported shafts. Okay. That's not it either.
Back in the day this was already done.It was done with the cheapest arbor head, small pulley drive to a larger motor below. The wheels were small if required and they didn't have to run 5000 rpm. There was Access to around the wheel. It already happened and there is plenty evidence.

[SteveM]

I have a bunch of wheels for my surface grinder, which has a 1/2" arbor, so they were made at one time.

Look for tool post grinder wheels.

The downside is that your surface feet per minute is going to drop with the smaller wheel. A 6" grinder is going to have around 3200 rpm, which is not fast enough for a 3" wheel.

I have a buffer that can take a wheel almost 20" in diameter, and it's only 1800 rpm for obvious reasons.

Steve

[John Hasler]

If you put smaller wheels on that grinder as it is, you may run out room. The motor head is so large that well, I, you can't quite swing the tool you are grinding. I believe that you had buffer polishing type units. Those had longer supported shafts. Okay. That's not it either.
Back in the day this was already done.It was done with the cheapest arbor head, small pulley drive to a larger motor below. The wheels were small if required and they didn't have to run 5000 rpm. There was Access to around the wheel. It already happened and there is plenty evidence.

I've got one of those. Don't have any small wheels for it, though.

[SteveHGraham]

Woodworking people are telling me to forget it. They recommend an 8" grinder with CBN wheels.

It looks like there are more benefits to CBN than I realized. The wheels cut much cooler than aluminum oxide because they're aluminum and absorb heat. Also, you can get them with abrasive on the sides so you can use the sides of the wheels safely. One of the most disappointing things about ceramic wheels is their tendency to explode when you grind on the sides of them. Another neat thing about CBN: you can get them with radiused edges to provide versatility.

For about $300, I can get two CBN wheels in different grits. One would have sharp corners on it, and the other would be radiused.

The only drawback I've seen is that you can't use them on mild steel. It loads them up.

[WJH]

Have you forgotten about Harold's treatise on grinders and what wheels to use, and his arbor design? Maybe he will ban you for your insolence.

[John Hasler]

Have you forgotten about Harold's treatise on grinders and what wheels to use, and his arbor design? Maybe he will ban you for your insolence.

Link please?

[SteveM]

Grinding wheels and HSS
viewtopic.php?f=44&t=75985

A grinder for HSS toolbits
viewtopic.php?f=44&t=76065

[SteveHGraham]

Have you forgotten about Harold's treatise on grinders and what wheels to use, and his arbor design? Maybe he will ban you for your insolence.

If Harold pulls anything, I'll declare a thumb war. He'll never expect that.

I got my white aluminum oxide wheels based on my careful study of the complete works of Harold. Thing is, he was advising us on high speed steel, which is impossible to ruin with heat. I have a lot of tool steel chisels and plane irons which don't get along well with aluminum oxide.

[Harold_V]

While it's true that my recommendations are for HSS, the wheels will work acceptably for carbon steel as well, assuming it's heat treated. The problem, and you identified it nicely, is that carbon steel, heat treated, is unforgiving of heat. Get the edge too hot and it's going to lose hardness, and it's easy to do.

One advantage to using a smaller wheel for this application is that it will behave softer than its rating. By choosing the right grit size, and bonding hardness, you may just enjoy success by switching to a smaller wheel. Pick a soft enough wheel and heating won't be much of a problem, either, at least no more than with most any other wheel. One negative of the small wheel would be the drastic reduction in radius in the grind. Easy to overdo, weakening the cutting edge. Might be best to do as you've been advised---use an 8" grinder, then select very soft wheels.

If you wish to keep heat down, don't diamond dress. Use a dressing stick, and use only a sharp corner, never a flat face, which will just dull the grains and create unnecessary heat when you grind. A hand dressed wheel cuts a lot cooler than one diamond dressed, a dodge we used to use when sharpening end mills on a cutter grinder. The finish isn't quite as nice, but by slowing down the speed of traverse, you can get an acceptable finish and keep things cool.

Thumb war. As if I'd be stupid enough to fall for that! Hmphhh!

By the by---what's a thumb war?

H

[SteveHGraham]

If you wish to keep heat down, don't diamond dress. Use a dressing stick, and use only a sharp corner, never a flat face, which will just dull the grains and create unnecessary heat when you grind.

I suppose I shouldn't point out that the diamond dressing tool I ordered about two days ago has a flat face.

[/quote]Thumb war. As if I'd be stupid enough to fall for that! Hmphhh!

By the by---what's a thumb war?

H
[/quote]

https://en.wikipedia.org/wiki/Thumb_war