Our Tech Dave, just shared this after a call he received:
The machinist was using a diamond tipped insert to face off aluminum flanges on pumps that he rebuilds. The pump manufacturer recently changed the type of aluminum that the flange was made out of but the machinist had no way of knowing exactly what it was and now he was not able to achieve the finish that he got on the old pumps.
He had been using a TPG-222 PCD tipped insert from Interstate. He was running at about 1300 RPM and .0017 IPR at an extremely light depth of cut. He was not able to increase the depth of cut because any stock removed has to be accounted for when the pump is rebuilt.
Dave suggested the machinist switch to a TPG-221 insert and increasing the feed rate. He surmised that the reason the finish was poor was because the insert was burnishing more than it was cutting (i.e. – it was deforming the material rather than cutting it) so the smaller nose radius should get better penetration into the aluminum and allow the insert to cut. The increased feed rate should help also. There will definitely be some adjustments necessary to get back to the finish he wanted but this is a good first step.
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