Cutting a 2"-4.5 UNC thread in a Mazak

[ridge_runner]

Hello everyone! Found this site while searching for help cutting the above mentioned thread. I am cutting 2"-4.5 UNC little longer than 3" in a material known as B-16 (heat treated 4140?) on a Mazak using the ISO side of the controler. I am using Valenite inserts. I have two problems 1. is the the a a little chatter on the first three threads that I can not seem to get rid of. 2. on the back edge of the thread I have alot of rubbing with a poor finish being a result. I am not a 100% sure of what is in my G76 lines but I will post tomorrow when I see them again. I have changed my speed from 100 to 600 RPM and best results have been seen at 450 to 500 RPM but still have the rubbing on the back edge. Can somebody help me out here? Thanks

[CoolhandLuke]

I've done a job similiar to that. The trick is to lean on your tools, I was doing them in 6 passes, no spring pass. Make sure your tool is on center that should take care of your rubbing. I was using Iscar tooling, that's all I use. Just seems to form a nice chip. You're going to eat inserts with that material. Just it should give you a nice shiny finish. Coolant is king, get it in the hole and on the tool tip. I was cutting on the side of my insert and taking less...the deeper I went. I did best at 700 RPMs or so. You have to put a load on the insert, let me know how you make out.

[Geof]

Sometimes you can get rubbing because the thread angle is greater than the side clearance angle on the insert. You can get wedge shaped anvils (?) that replace the flat one in the holder, to tilt the insert a little for extra clearance.

[ctate2000]

Use the Mazatrol side and program that tool to enter on 29 degress and cut only on the leading edge. Problem will go away.