I think even better, but more expensive, would be to buy some, I believe they're called "barrel" nuts or assembly nuts. They're a small rod section with a hole and threads cut cross drilled. You would simply make a tight hole for these to fit in to. Much stronger than grommets IMO.
A crappy pic, but hopefully illustrates the concept (a motor mount for a straight-line routing jig I made for guitar work...) |