Need Help Finishing Aluminum

[bgator220]

Hello All,

I am new to the forum. I am working on a cnc mill and milling a bunch of pieces out of small 1/8" aluminum sheet. These pieces have no hold down holes in them but I have made a set of clamps to hold them down well.

My problem is getting a good finish on them. I would really like to have a almost mirror polished finished on them without doing any polishing after they are on the mill. For the finishing, I am using a 4 flute 1/4" endmill, running at about 2900 rpm. I am using a g42 tool diameter offset, cut it out with a 1/4" at .29 diameter, .26 diameter, then put in the finishing bit and use a .25 diameter. So for the finishing pass I am taking off 5 thousandths. Does anyone know how I could get a better finish on them with the mill? Different tooling or speeds?

Im also looking to get some brushed aluminum sheets. I usually order from mcmastercar. Can anyone point me to a place to get better and cheaper sheets. I am getting a lot that are scratched up.

Thanks,
Brian

[bgator220]

What is a YT15? And why such the low spindle? what should my feedrate be with that setup?

Thanks