04-18-2015, 07:05 AM
I fail to understand why, if you already have good holders for WNMG and for CNMG inserts you feel the need to get yet another external holder for screw down CCMT/CCGT 09T30x size inserts. Sure, I get it that using a smaller insert allows you to have both turning tools and boring tools which use the same insert. Just keep in mind how much cheaper the WNMG and CNMG inserts are per edge. Because they are far more common, they are the same price or usually less per insert than a screw down, and you get at least twice as many edges because you can flip them over. You can't do that with a screw down insert.
Another consideration for external turning is you say you have to rough out square or perhaps flame cut crap into round. No screw down insert is going to be as strong as a negative rake CNMG or WNMG insert for that. True that your machine at 3HP is right on the edge of being able to use negative rake CNMG & WNMG, but they still make better economic sense. You may be losing sight of the initial goal, which when I read back to the beginning was to get more consistent finishes. That's definitely more a case of adjusting cutting speed and feed rate than choosing a screw down insert over the negative rake ones for which you already have holders.
I'm confused.
Another consideration for external turning is you say you have to rough out square or perhaps flame cut crap into round. No screw down insert is going to be as strong as a negative rake CNMG or WNMG insert for that. True that your machine at 3HP is right on the edge of being able to use negative rake CNMG & WNMG, but they still make better economic sense. You may be losing sight of the initial goal, which when I read back to the beginning was to get more consistent finishes. That's definitely more a case of adjusting cutting speed and feed rate than choosing a screw down insert over the negative rake ones for which you already have holders.
I'm confused.