OK I have my mill mostly running like a top but have a strange problem. I have been using 3/8" hss tooling for a lot of my cutting (.1 - .14 DOC/ slotting/ 35ipm). Runs like a dream. I chipped a bit and decided to throw on a carbide 3/8" bit I had. Both had same stickout (~1"), same cuts, same number of flutes(2) and the carbide SCREECHED. I had tried 3fl 3/8" carbide endmills and had the same problem but I thought it had to do with it being 3fl. I use a 1/2" 2fl and 1/4" 3fl with very little problems. My long 1/2" isn't the quietest but it is sticking out 2.5".
I know we can talk about harmonics and get into math that makes my head spin but is there things a non-professional guy can check? I have had issues with the spindle motor pulley slipping down the motor so I have fixed that but it was real finicky with belt tension. If it was were I thought it should be (barely any slop) the motor ran at 20% without being under load. I loosened it up and then the spindle would "hesitate". I got it where it doesn't hesitate and runs at 10% when not under load. When I start work for the day I have to run the spindle for at least 10-15 minutes to get it to come down. It usually starts at 18-20% and then warms up and drops down. Is this normal? Could it be that I the gibs aren't tight enough and this is causing it?
Any help would be appreciated.
-Keith