Originally Posted by rabbit
Jack nuts require large body hole diameter (7/16" dia. for 1/4" bolt). Require puller. Tendency to spin with corroded or cross threaded bolt and then you got fun. Outer flange sets proud of surface. I consider them light
duty junk. The rivnuts for aircraft installation are must more reliable but we always pulled them in epoxy sealer anyway.
This ^ rivnuts are a much better option but they too are subject to larger hole, correct installation tool (You can get one that will do 3 sizes of rivnut) highly suggest you epoxy them same as Jack said. If they break loose and spin it is a major PITA to drill them out in fiberglass, if you can't get to the back side. We would use a dental burr on a pencil grinder to grind the head off CAREFULLY. Most of us myself included would put a thin plate of stainless with the appropriate sized hole to fit over the head down first. Then grind so if you slip you do not grind into the fiberglass 15k rpm dental burr makes short work of going through fiberglass. There is another option if you are handy you can use nut plates ( Plate w/ floating nut crimped in place) they use two tiny rivets to hold them in place
. The have them in sealed and open style see http://www.cherryaerospace.com/files...og/CA-1031.pdf
for another style mind you using aircraft grade items gets PRICEY.
PS Jack in another life were you Air Craft Structural Repair also ?