I wanted a reasonable way to repair (two) broken horn buttons. It took a couple of tries to fine-tune it.
(http://foxtbirdcougarforums.com/attachment.php?attachmentid=15204&stc=1&d=1203928594)
One adjustment - I ditched the nylon screws for metal.
Parts:
6-32 x 3/4" machine screw
6-32 x 1/4" T-nut
#6 nut
#6 washer
#6 flat speed washer
Use a dremel or hobby knife to make a notch big enough for the T-nut to fit. Clear any remainder of the broken tab.
(http://foxtbirdcougarforums.com/attachment.php?attachmentid=15205&stc=1&d=1203928785)
Use a cutting wheel, tin snips, or wire cutter to trim the T-nut as shown ("after" to the left, "before" to the right)
(http://foxtbirdcougarforums.com/attachment.php?attachmentid=15206&stc=1&d=1203928785)
Final assembly. Use a washer, nut and a spacer to clamp the T-nut to the plastic.
(http://foxtbirdcougarforums.com/attachment.php?attachmentid=15207&stc=1&d=1203928785)
You might need to trim the flat speed nut to clear properly.