Need some advise from those who have come before me. I've been having fine luck on my 770 with aluminum and titanium and even some 1018 mild steel but I'm working with making some 2" 4140 parts out of typical annealed 4140.
Tried 3/16 4 flute, 3/16 5 flute and 5/16 5 flute, all tialn coated.
I havn't found a DOC much above .010 that doesn't just high pitch scream with chatter and leave patterns when the cutter engages. HSM routinely tells me I can take a .32"+ DOC, but obviously more DOC doesn't help chatter. What's odd is that even a finishing pass at .3 is no good. DOC as little as .09 still chatters. I'm working with HSMAdvisor and GWizard and I can 'make' cuts with proper chip load and they may even make a decent looking chip I just can't do it without unbearable screaming chatter.
I've clamped the stock in my 5 inch vise securely with parallels and currently have it clamped hard with Mitee Bite Talon Grips.
What kind of recipes or end mills should I be using for this stuff?
Other things I've tried: I've checked my lost motion in all axis and it's still the same as my inspection report (roughly .0004 in x and y and about .001 in Z). Any chance that isn't enough of the story and I need to dig into the gibs and preload? I've also got the tool holders marked to line up with the spindle to minimize runout. These tools that I'm trying to make work are all checking to .0004 runout or better at the flutes.