MACHINIST

[MERT]

HI
NEW TO THIS
MY ? IS I AM TRYING TO MILL A .140 WIDE SLOT THRU .700 ROUND
6061 ALUM THE SLOT IS .200 LONG
USING VMC W/O COOLANT THRU I AM PRE DRILLING EACH END THEN GOING IN WITH .125 ENDMILL ROUGHING OUT .06 DEEP WITH EACH PASS THEN
PROFILING TO .140 WIDE ANY IDEAS I KEEP BREAKING ENDMILLS
THANKS
MERT

[recordist]

After drilling the ends, I would "drill" the center of the slot with a .125 end mill.
Then use plenty of coolant, and cut the profile with the end mill (.060 is a fine depth of cut). If not coolant, plenty of air.

I would relieve the end mill (grind diameter a few thousandths smaller)! If your depth of cut is .06, all you really need as far as flute length is .06 (okay, a bit more than that, but...).

Any extra flute length will likely bind, and cause chatter in the ends of your slot - not to mention if your tool is a bit worn at the cutting end, when the full-size shank reaches the slightly-undersize slot, it will rub a bit and then break.

Hope this helps!

[mc-motorsports]

Make sure your using a 2 flute endmill.

[MFassler]

if your not using coolant you probably should if you have the ability(heh saw you said you dont have coolant thru)coolant thru is unimportant for what you are doing you just need to flush the chips out,otherwise take more cuts,yeah it will take a bit longer but you could up the rpm and feed quite a bit if you did it in say .020 deep passes. Also double check too make sure you are on centerline of the part. How are you holding the part? what brand VMC are you using and what feeds and speeds are you currently trying? more info the better. hope I was able too help.