[analogman]

See the attached picture - I am having a problem with finish. This finish was done with conventional milling.

I am cutting ovals 0.8" deep on 6061. I first do rough passes, then a finish pass at 0.010". Each pass is 0.200". Feed is 7.5IPM, Speed is 1200RPM. TiN coated HSS no-name endmills. WD40 lubrication. Conventional milling.

This is an RF45 CNC. I have gone through the machine and re-did all the gibs and AC bearings for the axis. I havent gone as far as tearing down the spindle.

I am not 100% sure of if my feeds and speeds are correct. I also think I can do better with a brand name end mill, BUT, is this really a problem with chatter? Any suggestions as how to proceed?

Here is a video of an earlier finish cut - I changed to climb milling, but it still has the same sound when cutting.

NOTE: this is of an earlier cut I changed to climb milling

[LongRat]

First of all it sounds like your spindle is making a ton of noise.. could be the gears in the head I guess, or is it Massey Ferguson powered? Check to make sure nothing is rattling loose there.
Seriously though, I have a three suggestions.

1. Climb mill, this will immediately improve your finish unless things are drastically loose, and hopefully they are not.
2. I know that machine in standard form has a slow spindle, but if you can, try to do something to increase RPMs. That's really, really slow for aluminium.
3. If it was me, I would take the whole depth of the finish pass in a single hit. This will reduce the chance of re-cutting chips which is being compounded by the conventional (rather than climb) milling direction you are doing.

[analogman]

I already mentioned that the video was an older one and I already switched to climb milling. The picture of chatter is from climb milling.

A lot of the noise is from the RF45 quill spline rattling in spindle - I am investigating options to secure it.

What do you suggest for feeds and speeds with 1/2" HSS endmill in 6061?

[CS900]

Check Out Our Omnibus List of Over 40 Ways to Improve Surface Finish When Milling or Turning - CNCCookbook CNCCookbook

[LongRat]

Well, on a finish pass like that I would probably be going slower than most may recommend and I would do 4000 RPM and maybe 350mm/min. A lot of that is down to the limitations of my kit though - may be different if I could run 12,000 RPM. An easy fix to try might be changing out the no-name cutter for something known and decent. A lot of the TiN coated no-name endmills have an extremely poor quality grind.
CNCCookBook is always a good read - recommended.

[WILDMAN2]

You need a sharp cutter for alum. that step tells me your cutter is not sharp