11-14-2012, 09:03 PM
Wow, excellent post Darren.
PVD (physical vapr depostion) coating is generally done at lower temps than CVD (chemical vapor deposition), and is usually a more expensive process. Because it's done at lower temperatures it can be a thinner coating (even though it's multiple coating layers) and can leave a sharper edge than CVD. Some coating can't be done via one process or the other. Yes, it's harder to find sharp inserts that are CVD coated.
I've found that the hard grade 5010, 907/908 and 9605 can fail at slower speeds in soft steel because the material may build up on the edge and then fracture the insert. At higher speeds or in tougher materials, more heat is generated in the chips and cutting zone and that helps prevent BUE (built up edge) failure. That higher speed applaction is when those grades work OK in soft steels.
As for the Valenite M7 chipbreaker vs Sumitomo's 24, they may look similar but in terms of scale they're quite different. The land on an M7 (I have some) is huge, and you need lots of power a feed rate to use it. The 24, not so much. ;) I did see that writeup on the Sumitomo AH725 grade, and now think it's completely different than the T725X you have.
PVD (physical vapr depostion) coating is generally done at lower temps than CVD (chemical vapor deposition), and is usually a more expensive process. Because it's done at lower temperatures it can be a thinner coating (even though it's multiple coating layers) and can leave a sharper edge than CVD. Some coating can't be done via one process or the other. Yes, it's harder to find sharp inserts that are CVD coated.
I've found that the hard grade 5010, 907/908 and 9605 can fail at slower speeds in soft steel because the material may build up on the edge and then fracture the insert. At higher speeds or in tougher materials, more heat is generated in the chips and cutting zone and that helps prevent BUE (built up edge) failure. That higher speed applaction is when those grades work OK in soft steels.
As for the Valenite M7 chipbreaker vs Sumitomo's 24, they may look similar but in terms of scale they're quite different. The land on an M7 (I have some) is huge, and you need lots of power a feed rate to use it. The 24, not so much. ;) I did see that writeup on the Sumitomo AH725 grade, and now think it's completely different than the T725X you have.