[lew52]

I am having difficulty turning 4150 steel on my Romi M-17 hybrid lathe. I have adjusted speeds and feeds accordingly but the finish is horrible. I've also tried different inserts but no luck. The material seems like it has some heat treatment to it. I have never used this material before so I hope someone has a suggestion or two for me.

[Geof]

If you are getting a horrible finish my guess is that your material is annealed or normalized. A lot of medium or high alloy steels like all the 41xx series are crappy to machine when they are soft.

What speeds/feeds have you been trying. I would try at 400FPM with a feed of 0.01" per rev and a DOC of no less than 0.05. No coolant, just an air blast. You need to find a sweet spot where the chips are peeling off blue.

[txcncman]

I pretty much agree with Geof. Get your surface speed up. Find a sweet spot for the depth of cut. You did not give particulars on the turned diameter, length of cut, or tool you are using. With a CNMG, 0.040 to 0.100 DOC 0.012 IPR feed. A WNMG might give you a better finish in this situation. Coolant or no really depends. You can try it with and without and see what works better. Machining is as much of an art as it is science. There rarely is one answer that works in all applications. You can use the published information as a jumping off point and use your experience and trial and error from there. Most engineer and manager types will never understand this.

[RICHARD ZASTROW]

There are many engineers and managers who understand "this". Actually, it's the bean counters fault. LOL

Dick Z

[txcncman]

Ok. You got me. I will have to qualify my statement with the phrase "in Texas". Most engineer and manager types in Texas will never understand this.