I'm thinking about playing around with making joint protectors.
I see 5/16 inserts available but haven't found 3/8 x 10.
Do I need to tap my own threads or can I just drill a hole and insert?
You'll have to drill a hole and tap it for 3/8-10 threads, no inserts for 3/8-10.
Yes, no need for an insert but if you really wanted to they sell blank inserts that you can drill and tap.
Yes Sir
They sell blank inserts but if there threaded 7/16's o.d, they're no go for 3/8X10.