Nuts and threads

thezappa · 9 Jul 2021 at 19:29

So I’m going to make a table, a decorative one I can keep a plant on and am going to make it with a concrete top.
To fix the legs I plan on using closed rivet nuts (took a bit of Googling to find out the name) set in to the concrete.
The nuts will be threaded and M8 size. My question is if I buy ready made wooden legs with a threaded bar set in the top how can I check the threads will be compatible? (Like these, they have an M8 dowel: https://www.etsy.com/uk/listing/600...=tapered+wooden+legs&ref=sr_gallery-1-1&frs=1
Is it the case that provided the bar on the legs is M8 they will have the same thread size as the nuts?
Example nuts: https://www.part-on.co.uk/product/m8-steel-countersunk-head-rivet-nut-100pk/

thezappa · 9 Jul 2021 at 20:47

Thanks for the input chaps. At least I don’t need to worry about a mismatched thread.
In terms of dome nut vs rivnut, I wasn’t set on using the latter I think ideally I’d want a slightly longer thread which in my head will offer a better fix and more stability. I’m not likely to put anything massively heavy on it.
I’m not concerned what the normal application of the nut is, one could argue concrete isn’t a normal material for tables although admittedly not that unusual.

For the nut not gripping in the concrete, it may be that I remove it before the concrete sets properly and fix it with epoxy adhesive but unsure how successful that would be.
The hex nut idea is a good one to ensure better grip when tightening the legs.

thezappa · 9 Jul 2021 at 21:01

That’s what started me down the road of a rivnut. A closed rivnut stops the concrete getting in. I realise I didn’t say that initially (the nut being closed).

thezappa · 9 Jul 2021 at 21:27

Ideally want to keep it under 30mm really. If the bolts are 30mm the thickness of the table top will need to be more than that. I was aiming for 20-25mm top thickness.

thezappa · 17 Jul 2021 at 17:29

My intention was to the create the form work and pour postcrete and position some rib nuts in place and let it set.
I hear what you’re saying about a wood table but I’ve made one of those already: