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Using a $30 made in china die grinder mounted in an ER 40 holder and running air instead of coolant on a HAAS VF-4.
Took a lot of mods on the machine to get the setup to work, but it's running really well for fine work such as fret slots and inlay.

That's pretty trick. It doesn't chatter and it's got enough torque?

Surprisingly smooth and doesn't notice that its cutting.
Just whirls away like a dentist drill.

I'm going to have to see if I can mod a tool holder to accept and direct air. My machine doesn't have through coolant capability. I like this idea because when something breaks or wears, it's a $50 fix instead of the $5K quote I just got.

Did some test cuts with the single flute cutters on Friday. It seems I can push them harder than the 3 flutes. Was doing full depth cuts at speeds that would break a 3 flute doing half the depth.

Pete, I noticed you removed the end piece (finger grip maybe) that surrounds the collet. Was that to provide a path for the exhaust? If not, how did you deal with the exhaust?

Hey Sheldon,
Gotta say first that I love your work!

It took two of us a couple week to sort through the problems of this set up and mod our machine (which didn't come equipped with the TSC option.)

We run a sealed line from the pull stud to the die grinder to get air in.
We allowed the exhaust to vent into the tool holder body and then route exhaust back out of a bushing that sits between the collet and the tool.
The bushing has holes drilled into it to allow the exhaust air to escape. An alternate solution would be to mill passages into the collet.
Our spindle is locked when using the tool so run out and balancing of the bushing is not an issue.
The exhaust air gives us some chip clearing as a bonus.

One idea, early on, was to drill exhaust ports in the side of the die grinder below the collet, however, we couldn't fully disassemble the die grinder to find out exactly where the holes should be.
I suppose we could have easily sacrificed one and split it down the length.
Another consideration was that we didn't know how may hours the die grinder would last so wanted a cartridge type solution that didn't require us to mod the die grinder every time it needed to be replaced.

If I recall, the end piece was cosmetic and posed a threat should it work its way off so we discarded it. Nothing to do with exhaust as the exhaust passage surrounds the inlet barb.

Thanks Pete. Man that must have been quite a chore plumbing for TSC.

I used a plain string to find the drill locations and am waiting on the JB weld to cure before hitting it with pressure. I think it's going to work though.

It was a bit of work. Luckily, we had the spindle covers off already to repair a leaky transmission gasket... ok, not lucky at all
In our case, there was a plug at the top of the draw bar that we were able to tap into. We ran air hose through the service loop to the back of the machine where we had installed another regulator.
We had to program the machine to precharge the draw bar to close the air circuit when running the air spindle. Without the bumping the draw bar air just rushed into the casting. The noise was quite startling until we figured out what was going on.

Let us know how your spindle turns out.

Thanks Pete. Did you need to add a rotating union to the top of the spindle to attach your airline to?

No, we milled a seal out of HDPE that sits under the pull stud. We have a stub line that runs between the air tool and the base of the pull stud. It's a snug, not tight, fit inside the seal.
That way we can fit our stub line to the air tool barb and push it into the seal before tightening the collet.
We don't spin the CNC spindle when using the air tool, so a rotating union isn't needed.

Thanks Pete. There's just one thing I don't quite understand. How did you plumb the compressed air into the spindle? Doesn't that need a rotating union?

I think you are running a Fadal, which is probably similar in operation (Haas originally copied the Fadal design)
Air line runs from a regulator and air valve at the back of the machine to a 1/8" npt right angle fitting we put at the top draw bar piston housing. Luckily for us Haas uses the same parts, minus a coupling seal (rotating union?), in both TSC and non-TSC machines.
The draw bar piston sits above the draw bar, which is a hollow tube, until a precharge bumps the piston down onto the draw bar. At this point there is a continuous air circuit.
The spindle cannot be allowed to turn during the precharge or the pistion will be damaged. (Normally, the precharge is a precursor to a tool change.)
At this point, we apply 24V to our air valve using a user programmed M code, it opens and starts the die grinder spinning.

Sheldon: You can get bearings from SDP/SI that'll replace the ones in your air spindle. They'll die sooner, but they're really cheap compared to sending it back for a rebuild ($20 VS $300). If it's an Air Turbine Tools spindle then they screw apart in the middle under the sticker and the nose screws out. You need the world's tiniest bearing puller to get the bearings out.

Pete: Run an extra finish pass at the bottom, it ejects enough of the packed in chips that they blow out with shop air. Changed my world when I figured that one out

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks for the tip Bob. What did you use to loosen the 3/8" slotted brass sleave that screws onto the spindle shaft? It can't be a socket because you need access to the flats on the shaft just ahead of it.

Thanks Bob,
Will give it a try.

Pete, what's the runout like on your grinder? I bought two and they were both .004"+.

Hey Sheldon,
We always do test cuts to get wear offsets for our bigger tools but never did on our fret slotting tools.
Our frets pressed in tightly without creating backbow with an .023 bit so it was never an issue. But it's something we should have done.

I don't have a slotted fret board around to measure so cant say now. .002 is kind of what I expect, but .004 could be in the realm of possibilities.

We're still set up for running metal parts right now (I hate metal chips) and probably won't get back to our wood setup for a week (have a lot on the go with shop machinery right now too.)
We're finishing the install on a rotary screw compressor that had a couple hiccups, learning how to use our ABB robot and waiting on a couple of 10 hp vacuum pumps coming from New Brunswick that we will rebuild. (Keep one and sell one.)

That's a good question...it's been so long that I don't remember anymore. My guesses from looking at it are that I either used some vise grips that were the right curvature or grabbed it in a collet and turned it off that way. Or used a small hook spanner...that seems like the most likely one. I'm going with small hook spanner.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks Bob. I've got a hook spanner on order for adjusting Micrometers. If it's not the exact right size I'm sure it can be tweaked.