Insert, 1/16" Groover HSS

T-15 steel holds an edge noticeably better than the carbide inserts I've burned through before, and the 1/16" width cut my external grooves dead-on. Took a few passes to reach the 0.25" depth, but it never chattered or chipped.

Cut the groove on a stainless shaft cleanly in one pass with no chatter. The 1/16" width is exactly as specified and the insert held up through a dozen cuts without any visible wear.

The T-15 steel feels properly rigid, and it held its edge through a full run of 0.062" grooves without any chatter. Depth to 0.25" is exactly as stated, so I didn't have to baby the feed rate.