I know this is a very general question and I will post more details about my specific situation as soon as I have access to my personal computer.

I am using a PC1100 with a Maritool 1/4" carbide 3 flute finishing endmill with flutes 1.25" in length on 6061. I am trying to take a .962" DOC cut and I am optimizing it using Gwizard to ensure I am running the correct feeds and speeds. So far if I use the finish setting on Gwizard I am getting a lot of chatter squeeling from the endmill and a poor surface finish. Set up is a TTS ER20 tool holder with a collet supplied by tormach. The stock is clamped tight in the vise and seems rigid enough. Using a fog buster with coolant.

Things I plan on trying:
- measure runout and try using a rego-fix high precision collet
- try different feeds and speeds from Gwizard

My basic question is has anyone successfully run a .25" endmill this long in a PC1100? I want to try and resolve my issue but I am wondering if the PC1100 is just not rigid enough to run an endmill this long and this thin?

Any insights and suggestions are greatly appreciated. I will post up more details on my setup tonight with pics of the finish I am getting.