Quote Originally Posted by Hirudin View Post
A few suggestions (I'll number them to make them easier to ridicule )

1. Do you know the helix angle of the bit you're using? A higher helix angle may reduce chatter. I accidentally recorded a video where I ended up comparing some tools with different helix angles. The tools also had different coatings and were from different manufacturers, which I realize makes for a poor test, but when I started I was just intending to record the performance of a single bit. Only after it started squealing like stuck pig did I end up changing to other bits. And it wasn't until I was done with the part and started editing the video that I realized the helix angle was probably the most important change.
I guess I should actually link to the video...
https://www.youtube.com/watch?v=CyNkCqthtog

2. I'm going to guess you're doing climb milling. You might consider conventional milling as apparently the angle of deflection varies between climb and conventional milling. That's what this CNC Cookbook article says anyway: Climb Milling vs Conventional Milling
(Look for the Tool Deflection and Cut Accuracy in Climb vs Conventional Milling section if you want to skip straight to the part I'm referring to.

3. You may actually get better results if you increase the WOC. With only 1.5 thousandths to bite on, your cutter might be making some super tiny/thin chips, which aren't ideal. I'd definitely recommend bumping this up if you switch to conventional milling (~10 thousandths (0.010") or so is prolly good).

4. Check out the feeds and speeds recommended by the nifty calculator CNCZone member Bryan Turner made. I plugged in your numbers (I think I got them all) and hit the button to turn the inputs into this link right here
Hopefully that works. I bumped the deflection down to 0.0001". Click the "Compute" button a few times to get more results.
The biggest problem I see is your ER 20 holder. It's just way too long for what you're trying to do. I would have used a 1/2 inch set screw holder to get the cutter as close to the spindle as possible.