I have read on this forum that other people were also having pull out issues so here's how I fixed it.

Before I installed Tormach's PDB, I was able to remove aluminum at a rate of about 3 cubic inches with a little bit of tolerance for chatter. This was using a 1/2" 3 flute aluminum rougher.
After installing the PDB, tool pull out got much worse. I was only able to remove aluminum at about 1.7 ci and had no tolerance for chatter. So any time saved with quicker tool changes was more than lost in lower MRR.

How I fixed tool pull out was installing a LYNDEX R8 collet. Unfortunately it took alot of fitting to get it right. When I first installed the new R8 collet, I wiped prusian blue on the taper of the collet. It showed that only a very small area of the taper was contacting the spindle. So using a 3M deburring wheel and a diamond lap, I was able to get 100% taper contact. This took most of the day and a least 30 check and recheck with the blueing. But after all that hand work the run out was .008" TIR 6" from the collet. So after another half day of hitting the high spot of the collet, I got it to about .0005" of TIR at 6".

Now I can use full spindle power and am back to a MRR of 3.1 ci and have good tolerance for chatter with out any tool pull out. I even did a worst case test were the cut was so deep at almost completely stalled the spindle...still no pull out. I'm not sure if it's the harder material of the LYDEX collet or the 100% taper contact that has fixed the problem but it was definately worth the effort.

I would be interested to hear how other peoples collets fit. Prusian blue can be purchased at auto parts stores but dark lip stick can used instead. It doesn't 'read' as easy but works OK. I think it is the reason some people have this problem and others don't.

Barry