today we were attempting to do some thread milling. First time for us and the results are not what we expected. Lookin to you guys to give some insight on whats going on or maybe thread milling should not be used in this material? Machine is a VF3/50, tool is kennametal tm25 parallel thread mill, using 14 tpi inserts, thru spindle coolant on, material is 8620 and clamped in vise rigidly, 15/16" thru hole, thread is 1"-14 to 1" depth, and using mastercam x4 for programming. Our issue is tool life, when we first started off, we were doing 2 passes to complete each hole ~800rpm, part turns out great but it sounded like the tool was not cuttin smoothly and assumin we are takin too much material each pass. Next we start increasing the number of passed and end up at 8 total per hole. sounds better but then inserts break. Next step slow down rpm ~400=broken inserts, increase rpm 1500 = broken inserts. try lowerin the number of passes, still breaking inserts, etc., etc. Basically we tried all kinds of shootin from the hip and broke the tool in the end. The completed threaded holes were all satisfactory, except a few during tool failure. We are using the feedrates vs. rpm that mastercam calculated.
Back to the ol ridgid tap, and cycle times are better as well. Where do we have it wrong? Any insight would be greatly appreciated. this is new to us.
thanks.