When we ran a full service chassis fab/turn-key hot rod shop a number of years ago, it was always useful to have threaded things around to weld into the frame for some kind of mount, etc.
Here’s a list of all our threaded things for your reference:
Weld Nuts - various threads
Product Details
Brand: Welder Series
MPN: NTWS214
Thread: Various
Buy 10 of one part number, get 10% off.
Buy 40+ to get 40% off! Sorry, no additional discounts applicable.
Available in 1/4-20, 5/16-18, 3/8-16, and 1/2-13 threads. Priced individually - buy what you need.
These threaded plates can be welded at each end, minimizing the risk of distorting the thread. The flat part on either side of the threads is 0.140″ thick, and the threaded portion is 1/4″ thick.
1/4-20: 1" x 7/16"
5/16-18: 1-1/2" x 5/8"
3/8-16: 1-1/2" x 5/8"
1/2-13: 1-1/2" x 13/16"