feedback with different ballnose bits

[aroff]

I'm playing with cutting aluminum
roughing, engraving and finish
anyone out there experienced in this
roughing no problem
finish different story
I thought using a 1\16 bit would give me a pretty finish with a small stepover but just a bunch of lines
am trying a larger bit like 1\8 for starters and work up from there
is my thought process wrong with small bit nice finish on metal

ty
andy

[Oldmanofgf]

Post your file if possible and give speeds and feed and depth of cut. It could many different things but I expect some kind of flex in the bit or your machine.
Glenn

[Oldmanofgf]

sorry I hit sent before I finished you need to use the biggest ballnose that will give you the detail that you need
Glenn

[martin54]

Size of the bit is a little irrelevant, really it comes down to a bit of experimentation. As there are so many variables what works well for one person on their machine may be completely wrong for you with your machine
Best thing is to do some test cutting varying the speed, feed, DOC & stepover with different tools & make notes on what works best cutting that material, obviously the settings for aluminium will be different for wood so you really need to do this for each different type of material you cut.
Your machine is not the most rigid of machines so you will probably need to use quite conservative settings, make sure you are cutting chips rather than creating dust, good chip evacuation is important as you want the heat carried away with the chips, the right grade of aluminium will also make a big difference.
What grade are you trying to cut ? You really need 6061 or higher to cut well

[nicksilva]

the best results is going to take lots of time.
I regularly do 3d figures in brass and aluminum. roughing is no issue - use what you got to hog it out.
For finishing, I use either a 1/16" or 1/8" ball nose with a 4 (yes a 4) percent step over. comes out as smooth as I can hope for.
so whatever you were using go down from there. but remember - every time you halve the step over expect it to quadruple the time it will take to cut.
cheers!