Hi All,
Sorry if this is slightly Off Topic (this is all related back to my Tormach 770 setup adventure, I can assure you), but I was really hoping someone here has seen this in their own TTS tooling, and might be able to provide some insight. I'd find it hard to believe if nobody else has ever run into this.
I've found that 4 out of 4 brand new TTS ER-20 collet holders and nuts are galling up collets and nuts during torquing, causing some of the "fingers" of the collet to twist around further than others. Thus, the final assembled tool holder didn’t have a nice, even collet “finger” spacing as expected, and had to be trashed! The tested TIR was idiotic... 0.005"... probably a result of the galling (and its location).
Here are pics of two of the tools in question:
All parts were de-greased, clean of debris, with both nut and holder tapers given a very light coating of light oil (Starrett tool & instrument). It's likely the threads got some of that oil too, but I'm not sure how much.
The collets were inserted over the eccentric ring in the nut correctly, and well-seated. Tools were inserted into the collet, the nut/tool screwed onto the holder body and then torqued down to 57 lb. ft. Used a new torque wrench, which probably had an error to within 5%. That was just an average of a few values I found in looking around, and even the guys at Tormach said that was a fair choice.
After disassembling, I noticed quite a bit of galling and scraping on the upper (30 deg) taper surfaces, on both nuts and collets. Tool holder bores and collets both looked great.
Here are a few snaps under the inspection microscope (this was a nice Maritool collet too):
Tormach tech was basically silent on the issue once I mentioned how much tooling I went through, which is really uncharacteristic of them. Sad. In the end, it should run about $200 to replace the toasted stuff using "reputable" tools, considering S&H. Anyone have experience with these standard and bearing nuts from Maritool?
Some of the guys over at Practical Machinist suggested a very light smear of anti-seize instead (on the taper of the nut I suppose).
Even with the risk, it sure would be nice to be able to use some of the brand new nuts (have 3 left). Should they still work at lower torque values? I might sacrifice one new tool holder and nut combo, and go for a stepped-torque test. Maybe Tormach will sponsor me? Who knows.
For those who have used Tormach-brand TTS holders and collets without seeing this kind of wear, how have you torqued and treated them during assembly?
Thanks!
-Mike