Need a fastener and don't know what it's called.

[Mark.Wilme]

Background :
The compass on our boat is at the helm on a pedestal. It is fitten with 4x 2" #8 SS self tapping screws. I am told and believe that the extreme cold is not good for the compass from an expansion / contraction point of view so seeing as I am replacing it (air bubble and cheaper to replace than to fix) I want to make it 'removable'. To my mind self tapping screws into fiberglass is not a long term solution. What I need is a gizzmo-widget, but Idon't know what it is called.


The Gizzmo widget.
I think I want to be fastening the compass with a set screw. This needs to fit into a female thread. The femal thread needs to be part of my gizzmo-widget that looks like a bolt and nut, but with an internal thread.


any ideas ? What is it called ?

[CharlieJ]

Are you referring to a T-nut? Those could be mounted under a flange, then regular machine screws could be used. They are available in stainless

[Tommy Bahama]

Not sure of a nautical term. In the aviation world (which most likely has it's roots in shipping and boat building) we have "nut plates" or "tinnermans". The nut plate is an actual nut made to rivet behind the mating surface. A tinnerman is a clip that attaches to the edge of a mating surface and accepts a sheet matal-type screw.

Hope that leads you in the right direction.

Tommy

[Mark.Wilme]

Are you referring to a T-nut? Those could be mounted under a flange, then regular machine screws could be used. They are available in stainless

If you mean a T-nut like this :-



then no, it has to fasten into fiberglass not wood. I guess I could fashion a piece of wood underneath and drive it (clamp it ) into that but I thought there would be something I could use directly in a fiberglass lip.

[Mark.Wilme]

Not sure of a nautical term. In the aviation world (which most likely has it's roots in shipping and boat building) we have "nut plates" or "tinnermans". The nut plate is an actual nut made to rivet behind the mating surface. A tinnerman is a clip that attaches to the edge of a mating surface and accepts a sheet matal-type screw.

Well, well, well - something like this may do the trick



I could use the same self tapper in the original hole, the threads catching on the 'tinnerman', not the fiberglass lip.

Good tip, THANKS

[Quetzalsailor]

Don't use the self tappers repeatedly; they'll soon cut the hole out to a larger size. An easy suggestion follows and then other ideas.

For relatively low stress applications, I have used filled epoxy (West plus their cellulose fiber stuff, or similar) in such holes and then drilled and tapped them. Use a longer length of threads than would be in a nut and take care threading the machine screws and it will be fine. Applications included: adjustment screws in wood harpsichord jacks, replacement fiberglass grilles for a Studebaker, sole access plugs (teak panels covering the keelbolts laying in recesses in the teak sole that I put in the Morgan 27)

For a place where I did not have much depth available, I counterbored the holes from behind and epoxied the nut into the counterbore. These were adapters, that I made of fiberglass, going between the 'glass deck and the flexible vinyl ventilation scoops for the engine. The scoops inevitably got sat or stepped on and the holes in the deck were the wrong size and accessible from within the lazarette (by a child), so the captured nuts allowed me to assemble the scoops without undue effort. I did the backer blocks and bolted connections for the seacocks similarly.

For places that are unhandy, I have made up aluminum backer plates and drilled and tapped them. Beats holding a loose plate, washer and nut all in alignment.

I have made cover plates in stainless steel and welded nuts onto 'em.

I have welded a bit of welding rod to nuts and variously glued, taped, or simply held the nut in place using the wire.

[dmairspotter]

Go to good old McMaster Carr and search for threaded inserts. Select threaded inserts for wood and plastic. Many types/materials.

Should have something for you!

[Peter]

I use Riv Nuts when no access to the rear of the panel is available.
Not as fancy as the above demo, I have a hand tool that came with a kit of various sized nuts. My bike rack on my car is held on with four 1/4" riv nuts and has held up for over ten years!

[Mark.Wilme]

McMaster car has these which should work really well.



But so would the idea of a tapped hole in an aluminium piece (or one of those T-nuts in a piece of teak epoxied in there too.

Thanks guys