[saabman]

There are a number of designs for "aux spindle" using routers, but has anyone outfitted the IH mill with a 30k-60k RPM air turbine grinder??

[Bubba]

I don't have an IH, but I did put one of the 5/8" dia. pencil grinders on my RF31.
I made a tapered collar to fit the lower end of the R8 area and of course it had a 5/8 bore. This was held on by a slit collar end and cross screw.
the upper end of the unit was made with another collar that fit the straight shank end of the R8 and screwed onto the end were the hose fitting originally went. Then a new drawbar was made from a piece of 1/4" brass pipe that screwed onto the upper end of the grinder and on the top, a threaded bushing was used to clamp the drawbar. Air was then fed down the new drawbar. Works quite well for engraving etc.
For a more heavy duty unit, I took a FRONT exhaust die grinder with about a 1 1/2" body diameter and removed the cartridge from its housing and made a new one from a piece of 1 1/2" pipe by threading it internally to fit the grinder, drilled and tapped a hole on the upper side of the pipe to fit an air coupling, and then made an insert to cap the top of the pipe with a 5/8" shaft out the top to insert into an R8 collet.

[saabman]

Interesting. How many CFM did those grinders consume. What did you do with them (Engraving, drilling, etc)

[Bubba]

The large diameter unit is rated at 4 CFM (90 psi) and the pencil one is rated at 2 CFM
The original intent was to use the pencil for doing pcb etching and drilling. I made the large diameter one as the pencil doesn't really have enough power to do engraving in metal. You have to do really light cuts to make it work.
Down side is these things are noisy (really need ear protection) and my 23.5 SCFM @ 175psi could not keep up with either on on a long run! So I have a feeling everybodys CFM ratings are bogus:{( Yes, I was running a regulated 90psi to the units.

I have subsequently built a small router to do the pcb and minor engraving work and use a 70 Watt electric spindle. Works much better.