Questions: self drilling/ tapping screws for chassis work

profdant139 wrote:
Cummins, thanks for the tip -- I see that the underside of the head is serrated, which will serve the same function as a lockwasher, I think??

If your using it on anything soft like corplast, use a large fender washer. That's what the trailer mfg do, and what I've found works well. Otherwise there is not enough area to support the corplast.

If your attaching metal pieces then then you need to decide if you need a washer for surface area support or not.