a15Mk1 alpha potentiometers

Hi there,
first of all sorry for this silly question...
I have an A15MK1 deluxe kit with alpha pot..they does not fit in the chassis...I mean there is a metal thorn (preventing the pot from rotate) on the front on every pot that prevents it to fit to the chassis so when I put one in the hole of the chassis it does not stick to the chassis because of this thorn that hits the chassis itself...what I have to do? (can I remove that thorn (how?))
Thanks a lot.
Kind regards.
Krusty