01-06-2015, 08:21 AM
Great question Jack.
The TNMG insert and associated holders would be the economical choice for just straight across O.D. turning, though I did notice your holder doesn't seem to have the steel "enveloping" the insert on two sides as most would. You do get six cutting edges on the TNMG inserts, all the same. It can be argued that the sacrifice is that the 60º included angle of the tip is weaker than the 80º of CNMG and WNMG, but in practice few home shops or commercial shops push an insert hard enough to see it.
With a CNMG43x insert you get the single most common insert ever made. There was a time that these were the only shape that you could get the newest grades, and where all the development was. These days, the makers release new product in CNMG, WNMG, and DNMG all around the same time, VNMG and TNMG get it last. I have seen a few cases where they never release certain grades and/or chipbreakers in TNMG, but that's not a dealbreaker for you.
The main advantage to using CNMG or WNMG as the primary turning tool is because it can also serve as the primary facing tool. You have the -5º lead angle on both tool approaches to the work because of the 80º included angle of the insert. You can take just as much of a cut in either direction. Yes, you can face with a TNMG insert, but only up to about the nose radius for depth of cut. Moreover, some of the commercial shops pick up holders that present the "opposite" 100º corners of the CNMG insert and use it for heavy rough turning or facing. The negative lead angle is VERY strong.
I don't have a holder for TNMG or I'd probably use them now & then. The DCLNR164 and DDJNR164 holders I have for CNMG43x and DNMG43x inserts (respectively) are my No.1 and No.2 "go to" holders and insert combos. I think my MVJNR163 holder for VNMG33x inserts may actually fall behind the MSDNN164 holder I have. That one holds square SNMG43x inserts at the 45º lead angle so I constantly use it for making chamfers/breaking sharp edges.
To answer you question in simple terms: I'd use the MCLNR holder and its CNMG inserts as the main one for both turning and facing.
The TNMG insert and associated holders would be the economical choice for just straight across O.D. turning, though I did notice your holder doesn't seem to have the steel "enveloping" the insert on two sides as most would. You do get six cutting edges on the TNMG inserts, all the same. It can be argued that the sacrifice is that the 60º included angle of the tip is weaker than the 80º of CNMG and WNMG, but in practice few home shops or commercial shops push an insert hard enough to see it.
With a CNMG43x insert you get the single most common insert ever made. There was a time that these were the only shape that you could get the newest grades, and where all the development was. These days, the makers release new product in CNMG, WNMG, and DNMG all around the same time, VNMG and TNMG get it last. I have seen a few cases where they never release certain grades and/or chipbreakers in TNMG, but that's not a dealbreaker for you.
The main advantage to using CNMG or WNMG as the primary turning tool is because it can also serve as the primary facing tool. You have the -5º lead angle on both tool approaches to the work because of the 80º included angle of the insert. You can take just as much of a cut in either direction. Yes, you can face with a TNMG insert, but only up to about the nose radius for depth of cut. Moreover, some of the commercial shops pick up holders that present the "opposite" 100º corners of the CNMG insert and use it for heavy rough turning or facing. The negative lead angle is VERY strong.
I don't have a holder for TNMG or I'd probably use them now & then. The DCLNR164 and DDJNR164 holders I have for CNMG43x and DNMG43x inserts (respectively) are my No.1 and No.2 "go to" holders and insert combos. I think my MVJNR163 holder for VNMG33x inserts may actually fall behind the MSDNN164 holder I have. That one holds square SNMG43x inserts at the 45º lead angle so I constantly use it for making chamfers/breaking sharp edges.
To answer you question in simple terms: I'd use the MCLNR holder and its CNMG inserts as the main one for both turning and facing.