> From: andy pugh [mailto:bodge...@gmail.com] > On Thu, 10 Nov 2022 at 01:03, John Dammeyer <jo...@autoartisans.com> wrote: > > I think it was on this forum that the discussion came up on the holding > > power of R8 collets and how they were essentially only useful for light > > machining. > Why not experiement? > > Put a bolt (ideally of the same material and surface finish as your fly > cutter) in the collet. > Torque the drawbar to a low value. (with a torque wrench) > Measure the torque to spin the bolt in the spindle with the same wrench. > Increase the drawbar torque > Repeat. Several times. > > Now plot the graph of drawbar torque to tool torque. Now you know, > > Then you need to compare the to the torque the flycutter needs to operate > at various depths of cut (unknown :-) > I guess to do that sort of experiment, and I have considered that, one has to first buy a few disposable R8 collets. The moment the tool spins it's likely to damage the surface isn't it?
I read that collets tend to be hardened. I guess in the same way that the jaws of a jabobs chuck are harder than the drill bit. After all who doesn't have a drill bit that spun and has marks. But I've seen some pretty rough chucks too. The Tormach TTS system manual states that tooling shouldn't be any larger than 1/2" and that certain types of cutters are more likely to twist and/or be pulled out. What brought this all to the forefront was watching a series of youtube videos where a hobbyist was trying to create a power draw bar with enough holding power so he could do heavy cuts. He went through a number of iterations and talked about using 100's of Newtons to hold his tooling. (Looked like home made TTS types). I think for the size of his machine and R8 tooling he was expecting too much. I guess though your idea of measuring the torque to twist the tool or tool holder based on draw bar torque is still the best idea and not that hard. Not sure how to work the math back to a spindle turning a 3/4" end mill at 600 RPM with too deep a cut so that the end mill jams. In my case the V belts will slip I think, or the servo drive will fault. It's if it jams and slips that is the issue. Thanks for your feedback. John _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
