With a knife-edge file, cut notches all around, making sure the
left side of the notch
(the face that will do the cutting) meets the end
at about a 90° angle. Also make sure there is some flat
area left on the end of the tube, to prevent the tool
from trying to cut too fast and getting stuck. You might be able
to achieve the proper effect just by cutting slits with a razor saw.
When you've cut enough notches, remove the burrs from the inside of the tube with a small round file.
Slide the tube over the truck mounting pin, and turn it by hand as you would a regular drill. It should scrape off a little plastic as it turns. If the truck mounting surface is wider than 5/32", be careful not to cut too deep, as you won't see the bottom of the groove until you remove the tool.