Munkul
Jack of some trades, Master of none
- Messages
- 7,370
- Location
- Cumbria
Playing about with some crappy 40mm black bar on the lathe to see what sort of surface finish I can get. Usually I just accept what I get, but best learn this stuff now before I get a job it matters on, eh?
Same tool, same setup. 1000rpm, 2mm DOC, 5 TPR, and the tool rotated so swarf can't catch and mar the finish. Centre height set for each.
The best one is the top one. Chips break properly, and gives a mirror finish. No chatter marks. Works great on just about everything as long as you feed it in hard enough.
The middle one works OK. Chatters a bit towards the free end of the bar, but still gives a mirror finish. Fine, it is a roughing insert after all. But I can't get chips to break, it just gives long hot strings that are strong enough to choke a man. Maybe it's the soft material.
The bottom one is crap. It should be the sharpest of the bunch and work with shallow cuts, but no matter what I do, it chatters and gives a crap finish all over. Faster, slower, deeper, shallower, hot, cold, whatever.
Now I understand the designations and nose radius etc, but going on the limited knowledge i have, the bottom insert should be better for shallow cuts and give a better finish... But it doesn't.
So... What am I missing? Good people of the forum, please tell me what my random ebay inserts are doing
Same tool, same setup. 1000rpm, 2mm DOC, 5 TPR, and the tool rotated so swarf can't catch and mar the finish. Centre height set for each.
The best one is the top one. Chips break properly, and gives a mirror finish. No chatter marks. Works great on just about everything as long as you feed it in hard enough.
The middle one works OK. Chatters a bit towards the free end of the bar, but still gives a mirror finish. Fine, it is a roughing insert after all. But I can't get chips to break, it just gives long hot strings that are strong enough to choke a man. Maybe it's the soft material.
The bottom one is crap. It should be the sharpest of the bunch and work with shallow cuts, but no matter what I do, it chatters and gives a crap finish all over. Faster, slower, deeper, shallower, hot, cold, whatever.
Now I understand the designations and nose radius etc, but going on the limited knowledge i have, the bottom insert should be better for shallow cuts and give a better finish... But it doesn't.
So... What am I missing? Good people of the forum, please tell me what my random ebay inserts are doing