08-28-2015, 08:01 AM
My only issue with any of the fly-cutters which use carbide inserts is that of the inserts themselves. Since TNMG inserts were developed for turning, the bulk of the grades available are harder and intended for continuous turning operations.
Of course today's carbide is far better and stronger than when TNMG's were first available, so perhaps a moot point. You can get some very upsharp geometry in that shape insert now. Look for TNMP or TNGP and they'll have a very positive chipbreaker. In grades, most makers now include data which will state the relative toughness versus hardness (and wear resistance) of the grade. For the interrupted cut of fly cutting, look for values such as P30/M30 or higher numbers, rather than P10/M20 type of numbers. Both will work in finish cuts, though the tougher grades will sustain even slamming into flame cut crappy steel.
Of course today's carbide is far better and stronger than when TNMG's were first available, so perhaps a moot point. You can get some very upsharp geometry in that shape insert now. Look for TNMP or TNGP and they'll have a very positive chipbreaker. In grades, most makers now include data which will state the relative toughness versus hardness (and wear resistance) of the grade. For the interrupted cut of fly cutting, look for values such as P30/M30 or higher numbers, rather than P10/M20 type of numbers. Both will work in finish cuts, though the tougher grades will sustain even slamming into flame cut crappy steel.