[ericscottf]

Hi all,

I am working on a custom piece of equipment which involves getting an abrasive grinding wheel into a very tight spot.
The wheel is a cylinder, .55" dia, .15" height. The shank is .092" dia and 1" long.

I need to turn the wheel 1k-4kRPM, so no big deal there.

I'm trying to find a collet, taper, drawbar, etc, that has an OD that is smaller than the wheel so i can get it in place. I'll put some bearings and a small timing pulley on the shank of the tool holder so i can drive it from outside. The torque on the wheel will be negligible.

Ideally, the OD of the largest part of the tool holder would be .4" Not an easy order, I know.

I've found plenty of WW collets that would work well, but nothing to put them into that winds up as a shank.

A pin vise would be perfect, but that's a hand tool and rather inappropriate for this setup indeed.

What's the equivalent of a pin vise that would be good for mounting in a pillow block and driving at 1-4k rpm?

thanks!

[DICKEYBIRD]

Eric, you might take a peek at one of those cheap air powered pencil grinders from HF. They're on sale for $22.99 and there may be something you can salvage out of it to get you started?

I have one but it's at home. I think the chuck is bigger than you want though. The collet is made for a 1/8" shaft but that's no hill for a stepper. (Might qualify as a decent pun.)

[Dylwad]

Tall order, maybe post an rfq to have a set screw shank made, would be super simple for most good machinists to make.

Or if you have a small lathe, turning a pin vice down between centers could be an option, just not sure how concentric the collets are on them.

The pencil grinder is a good idea, but they are hard if not impossible to find with a .092" collet, and not sure of the runout on the cheapies.

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[packrat]

Pretty sure dental hand pieces use a .092 collet. Or at least they did. Dentist gave me a bunch of burrs one time and the shanks were .092.

Here's a link to the Foredom collet I used -
http://www.foredom.net/hp4117.aspx

[Dylwad]

Pretty sure dental hand pieces use a .092 collet. Or at least they did. Dentist gave me a bunch of burrs one time and the shanks were .092.

They do, but the clamping isn't always the general collet type, they can have a funky flat on the end for quick changes.

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[DICKEYBIRD]

Here’s some info on the HF Pencil Grinder. The clamping nut is .390” O.D. by .285” long,; the 2nd part with the 3 grooves (front cover) is .531” O.D. just behind the nut & flares out to the main body size of .627” by .655” long. It does have a 1/8” collet but couldn’t you easily source your grinding wheel in that size rather than .092”?

Sorry, I’m not gonna take it apart but there are 3 ball bearings in the thing according to the breakdown page (good news). You can cut off the portion of the front cover back to the rear of the wrench access slot which would give you a .390” collet chuck .725” long. Looks like there’s enough widgets in there to warrant cutting it up & grafting on a home-made pulley & spin it up with a small 12 or 24vdc brushed motor & belt.

If you really want to be cool you could make up an adapter to graft on a direct drive brushless outrunner R/C airplane motor!

Anyhoo, I hope this helps a bit and if you make a bazillion $$ with my idea, be sure to share the wealth!

[pippin88]

Can you not just use an extension shaft?

If not you'll need to tell us the maximum length (space) you've got

[kennl]

I've made a couple of these. They work pretty well for what they are.



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[wizard]

Hi all,

I am working on a custom piece of equipment which involves getting an abrasive grinding wheel into a very tight spot.
The wheel is a cylinder, .55" dia, .15" height. The shank is .092" dia and 1" long.

I need to turn the wheel 1k-4kRPM, so no big deal there.

Get a quarter inch piece of drill rod, drill a hole in the end of it and Loctite the wheel in place. Then chuck in the spindle of your choice. Honestly though 4K sounds a little slow.

I'm trying to find a collet, taper, drawbar, etc, that has an OD that is smaller than the wheel so i can get it in place. I'll put some bearings and a small timing pulley on the shank of the tool holder so i can drive it from outside. The torque on the wheel will be negligible.

How tight is tight. Silly question but there are numerous ways to get creative here. Further is it heavy production or just a few parts.

Ideally, the OD of the largest part of the tool holder would be .4" Not an easy order, I know.

That is easy just go the Loctite route described above. The issue then becomes length and what you are allowed there.

I've found plenty of WW collets that would work well, but nothing to put them into that winds up as a shank.

A pin vise would be perfect, but that's a hand tool and rather inappropriate for this setup indeed.

Most pin vises also have a lot of runout.

What's the equivalent of a pin vise that would be good for mounting in a pillow block and driving at 1-4k rpm?

thanks!

Your clearance on diameter seems to rule out most collets. Your other option is a set screw in a drill rod extension.