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Carbide Turning Inserts, What flavour do you prefer?
Hi all,
In the diamond tool holder thread an interesting discussion started about CCMT and CCGT inserts. I have been meaning to start this thread for a while and said discussion reminded me about it.
So i'd like to know, what do you use for external turning and why?
I still use the first holder i got, an iscar MWLNR, which holds WNMG 06T3 inserts. This was sold to me by my local shop when i first got my lathe. These holders have 5deg negative rake both axially and radially. The inserts have 6 points but generally you only get 4 or 5, by the time you knock a corner off and it chips right down to the opposite side.:doh:
I have just finished a box of WNMG 06T304 PP (positive rake) IC9250. The 04 is the nose radius, .04mm. The have cut well and given decent surface finish at 150m/min and at least .6mm DOC. The biggest problem is cutting to size trying to take such a cut on a small lathe. Generally the best i can do is get within .05 this way. Trying to take a little .05mm cut leaves an appalling finish of course.
I just bought a box of 06T308 TF (changing rake angle along the edge) IC8025 inserts. They are not as tough as the 9250, but the nose radius makes up for this somewhat. These seem to excel at facing but need really good rigidity for general turning. They do however give a great finish at a lower DOC. The pic below is of progress on an ER40 collet chuck, diameters and 70 and 50mm. The finishing cuts were done at 1250rpm DOC .2mm.
I have some GN (general) inserts in the mail, and am trying to find some SF (super finishing) ones to try.
The only other inserts i use are CCMT in a small boring bar, but i'm sticking with OD turning for now.
Cheers,
Ew