QC30 - Tool Holder Falling Out of Spindle

Hello, I own a Bridgeport Boss 5, with what I believe is a Series 2J head. It has the Erickson QC30 spindle. It works fine when taking very light cuts, but today I was taking a (fairly conservative cut) with a 1/2" Carbide End Mill. It was all going great until the tool holder fell out of the spindle suddenly, destroying my work piece and tool.

This has happened 3 or 4 times with this machine now. It has a solid spindle with no drawbar or hole for one.

Has anyone run into this issue before? What can I do to prevent this? The spindle nut was incredibly tight.

Yup mine did the same thing until I figured it out. Loosen the nut another half turn or so, insert the tool holder, hand tighten about a half turn, the tool holder should still be loose. Make sure the tool holder is engaged in the spindle dogs. Try to pull the tool holder out, if it won't come out then tighten the nut and you should be good to go.

If you still have some trouble I'll post some pictures.