I'm assuming I just got in a hurry and didn't tighten the drawbar enough, but I was doing a long full width cut with a HSS 1/4 4 flute endmill (3.45 IPM at 1200rpm) and it started cutting deeper and deeper. After investigating, I found that the TTS holder had pulled out of the TTS/R8 adapter.

Luckily I didn't mess anything up. What did I do incorrectly? How tight do you tighten the drawbar?