The noise could also come from a dulled cutting edge on the end of the mill or possibly chip welding. I have got a few import endmills that were not all that sharp out of the pack. On 6061 they possibly could have made a squealing sound but they would have been hot also and the surface finish would have been terrible. They were used on large equipment so they were taking heavy cuts and were only used for roughing so it didnt really matter. As far as the Collet vs. Endmill holder debate there is alot of debating back and forth with everyones opinion, to my knowledge there has not been any actual proof in the pudding tests that show one way or the other. This I do know. I have had endmills slightly slide out in a collet during heavy cuts which ruined a few parts in the batch until it was caught. The collet was name brand used very little with the correct size mill and it was tight. The movement was only .0025" but that was enough on that job. For roughing I will always use a setscrew type holder other than that either has proven adequate to me. Alum., Stainless, Toolsteel, Titanium I have used both in each and it is about the same story. With your depth of cut and feed in 6061 I would use either, but if I had a problem I would definately try another holder to rule it out if nothing else comes to light. Just my 2 pennys though.  |