What kind of glue should I use to hold the PKCrushgrind insert in the cap? I used epoxy only to find out it will not adhere to the plastic.

I just finished the best looking pepper mill I've ever built and intended to donate it to a Relay for Life auction tomorrow night. It worked fine until I had the bright idea of putting peppercorns in it. Forget it! The first slightly hard peppercorn caused the cap to spin on the mechanism. This is the first time I've used the crush grind mechanism and unless I find out I did something stupid, it will be the last.

Any suggestions will be appreciated.