what "nut" am I looking for, please?

No not really. It is a blind nut that acts exactly like a rivet would. i.e. it expands behind the GRP to hold and is not like a rawl bolt that expand in the hole to hold. What you are after if you want to countersink a nut into GRP without a hole going right through the GRP is a threaded insert as EU cruiser pointed out. That you thread in but lock with glue

51w9D4gjSmL._AA160_.jpg
 
Re: Big head!

Any advance on the big head female something.......is that really what it is called!
Right..bind nut..no, a threaded insert...well done sir.
So I might need two....probably cheaper to buy 500!
Thanks all....
 
BruceK said:
No not really. It is a blind nut that acts exactly like a rivet would. i.e. it expands behind the GRP to hold and is not like a rawl bolt that expand in the hole to hold. What you are after if you want to countersink a nut into GRP without a hole going right through the GRP is a threaded insert as EU cruiser pointed out. That you thread in but lock with glue

51w9D4gjSmL._AA160_.jpg
Click to expand...

Has anyone found some stainless ones ? All the ones I have found are some diecast zinc alloy ones; very prone to corrosion even if fresh water gets to them.
 
Mike k said:
that's really useful and been added to my 'favourites' - thanks. I have just had a Jabsco remote spotlight fitted on the radar arch - do you reckon these would have done the trick?
Click to expand...
Minimum order for 316 stainless is £30+ vat + delivery; that is quite alot for two nuts as I need!!
 
BruceK said:
No not really. It is a blind nut that acts exactly like a rivet would. i.e. it expands behind the GRP to hold and is not like a rawl bolt that expand in the hole to hold. What you are after if you want to countersink a nut into GRP without a hole going right through the GRP is a threaded insert as EU cruiser pointed out. That you thread in but lock with glue

51w9D4gjSmL._AA160_.jpg
Click to expand...

I can't see that having any strengh in a few mm of GRP. Surely you need something with a greater and flatter surface area that can be glued or glassed in?
 
petem said:
I can't see that having any strengh in a few mm of GRP. Surely you need something with a greater and flatter surface area that can be glued or glassed in?
Click to expand...
Oh no.. are we back to the Bighead fitting again ?!
If you can get behind the grp I guess you can epoxy something in before drilling through the grp.
 
petem said:
I can't see that having any strengh in a few mm of GRP. Surely you need something with a greater and flatter surface area that can be glued or glassed in?
Click to expand...

If it's a few ( a few being 5-7mm) mm of GRP use the rivet nut. If one nut did everything you wouldnt need several types. As for threaded inserts remember they can also go in from behind, and yes, they do hold. Most certainly using the bolt described by the OP. I have them on a number of units from car bumpers, grills etc to motorcycle fairings and they are good for up to a specified 15NM torque, and a lot more trying to undo them a few years down the line. Of course if the bolt threaded in is holding down considerable torsion forces then no, these would not do. But again, this was not in the OP's specs.
 
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