Reply To: TNMG insert

[Paul FallertParticipant @paulfallert28101]

Quality TNMG inserts are able to take moderate interrupted cuts without chipping. Higher RPM seems to fix  problems with carbide inserts (and this was a difficult transition away from slow and careful). The quality holder I purchased from PlasTools 10 years ago is a "turn and face" style. You set it to face without a pip and then you begin turning.

I made this drawing to illustrate the differences of TNMG vs TNMP (the TNMS is 20° compared to the TNMP's 10°. Note that these inserts must be mounted in a tool seat at a negative rake. In the illustration, the seat is approximately 7° compared to the phantom green base line. TNMP do not like interrupted cuts.

The width of the land determines the minimum cut. If you take cuts less than .005", the insert will not be cutting in the positive ramp area behind the LAND, so it will exhibit tendencies of other negative rake tools (higher pressures, not-as-nice finishes). The TNMG inserts I have used have a very narrow land and I can remove .001". Eventually this land wears from heavy use and you then won't be able to take fine cuts. But, the price per insert tip (6 tips) is attractive and if you follow the guidelines, the name brand TNMG inserts last a long time.

At higher rpm, the chips turn blue, the insert stays cool, the workpiece stays cool and the finish is very nice. Try .025" (radius) cuts in mild steel at 300 sfm and see what TNMG will do on your machine.

Edited By Paul Fallert on 21/07/2017 17:57:36

Edited By Paul Fallert on 21/07/2017 17:59:24