Nylon engine-mounts: self-tappers or through-bolts?

[Nigel R]

Can't see vibration causing issues myself, as Paul says it's like screwing into a giant nyloc.

 

If you want to use through bolts, go ahead, both methods work.

 

Something else. I use a dremel cutwheel to cut into a screw, then use this to kind of cut a thread into the mount after drilling pilot holes. 

[Andy Stephenson]

1 hour ago, Nigel R said:

Something else. I use a dremel cutwheel to cut into a screw, then use this to kind of cut a thread into the mount after drilling pilot holes. 

I've used this method to clean out bulkhead threads in locations where a tap and tap wrench would not access but by using a caphead screw cut this way to effect a crude tap and a ball head Allen key it's an an easy fix.

[Mike T]

7 hours ago, Paul De Tourtoulon said:

Screwed into plastic is like a nystop nut but with 10 times more surface...

Absolutely spot on.  I wouldn't self-tap into metal or wood mounts, but into GRP designed for the purpose - why not?

 

The only problem is getting the pilot hole just right.  The temptation is to drill undersize for a really tight fit, but that risks shearing the screw head.  If you get the hole right and use proper Parker Kalon (or equivalent) screws, then there'll be no problem.