Originally Posted by
Jim Dawson
In aluminum and other easy to machine materials deep cutting works great, but sometimes you are limited by the insert. On my machine I can peel about 0.875 inch off of the diameter of aluminum, but in SS I have to be a lot more conservative, not because the machine lacks HP or rigidity, but rather the inserts just don't last long, and I have tried a number of different inserts, including the expensive ones.
4140HT is pretty tough stuff, if the inserts live at 120 SFM, then try 240 and see what happens. I just experiment until I find the best combination for the job.