Don't use them.
I use SS cap screws for most and studs with nuts for others.
If you work it right, you can drill each cap screw for safety wire and they do not unscrew. There are ones that are so tight that you need to work the nut on as the header is screwed in place.
I have a lathe, so I also found that I need to put a 45 degree angle on a couple to center the header flange to the head and to get better retention.
I highly recommend SS cap screws drilled for safety wire.
Old trick.
