This is a bit off topic, but what kind of partoff tool can you find that will reach 4 inches? I've shopped around a little, and have only found the standard 6" blade (which will reach 3" radius if you baby it) and the next increment blade seems to be some gawdawful thing that will part off a 24" bar taking a cut 1/2" wide
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)