Threading with inserts

[PixMan]

I thought it would be good to share more about the threading I did yesterday. I needed to thread 5 different parts with 4 different threads of 2 different leads.

I used full form (cresting) lay-down style (ER) carbide threading inserts. There were two different leads, so I bought two Vardex 16ER1.5ISO grade VSX. I already own 5 of the Carmex 16ER1.25ISO grade MXC. I believe the Vardex grade is PVD TiAlN coating, and the Carmex is PVD TiN coating. The grades are high cobalt content for lower speed rates but high toughness against chipping.

Here's what the Vardex insert looks like after making (1) M25x1.5, (1) M20x1.5, and (2) M14x1.5 threads in 316 stainless steel.


Here's what the Carmex insert looks like after making just ONE M12x1.25 thread, also in 316 stainless steel.


Now here's a better photo of the M12x1.25 thread, which I posted elsewhere yesterday. You would be hard pressed to get a higher quality thread with anything other than thread grinding.


It is especially preferred to use full form threading inserts when making metric threads because they are specified to have a given radius @ both the root and the crest of the thread. With "UN" (Unified National) inch sized threads, the crests of an external thread are flat, the root only is a radius. Lay-down threading inserts for those DO also cut the flat on the crest of those threads. Using hand ground HSS tools you are always compromising, though that's often overlooked in the home shop.