Face Milling Lock bar Reliefs

JRB Blades

JRB Blades

Knifemaker / Craftsman / Service Provider
Joined
Jul 22, 2013
Messages
266
I have been using my LMS 3990 to face mill the lock bar reliefs on my frame locks/liner locks. Normally taking them down to .045 thickness or so. I am using a 5/16" carbide ball nose end mill. The titanium scale is secured in my vice and feels pretty solid in there. Problem is whenever I go to mill the lock bar relief, I get tons of chatter from the end mill. Doesn't matter if I'm conventional or climb milling. Doesn't seem to matter how fast or slow I am moving the table (X axis) or how deep or shallow I'm moving the vice into the end mill (Y axis). What RPM do you guys run your carbide end mills to mill the lock bar relief? Seems I've tried around 300 RPM up to 2400 RPM and it still chatters and shakes the whole mill. Is my mill just too small to do this maneuver? Thanks for the help.
 
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Natlek said:
You mill relief before you cut liner or after?
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After. Maybe that is making it too unstable? I make the long lock bar cut, but I don't release the lock bar until later on.
 
A Picture of your setup could tell a lot. …

“secured in my vice and feels pretty solid in there.”
 
Maybe reduce your depth of cut. Meaning retract the end mill up and make your cut and then step it down and do it again and again etc. your last finish cut could have full engagement from top to bottom if it's very shallow and you're turning very slow, but remove the bulk with the tip of the end mill in steps
 
Nathan the Machinist said:
Maybe reduce your depth of cut. Meaning retract the end mill up and make your cut and then step it down and do it again and again etc. your last finish cut could have full engagement from top to bottom if it's very shallow and you're turning very slow, but remove the bulk with the tip of the end mill in steps
Click to expand...

Gotcha. I will try that. What RPM do you suggest? 700ish? Also, when I retract the end mill up, do I make a light pass (.005 or so) and then go down or do I do my full cut (.115) and then step down and do another full cut?
 
Yeah you need to mill the relief before cutting the lockbar out (or at least before you cut it out fully). Try it and see if that makes any difference
barlowchiro said:
After. Maybe that is making it too unstable? I make the long lock bar cut, but I don't release the lock bar until later on.
Click to expand...
 
I'll try milling it before the lockbar cut and also put a backer piece to try and secure it better.
 
I agree with N Natlek . A plate between the titanium and back jaw of your vise to support the backside could be the simple trick that makes all the difference. Then a shallower axial depth of cut to rough it if that doesn’t work. Finish at full depth with a light (.005-.01) radial cut.
 
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Mancipia Mariae said:
did it work out?
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Yea, it did cut down quite a bit with an aluminum plate backing the handle scale. Didn't notice much difference with cutting the lock bar before or after milling the relief though! Thanks for all the tips guys!
 
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