J bolts

[Dave221]

Hello all,
Could I ask if anyone knows where I can source galvanised ‘J-bolts’. I need 4 bolts for my pending observatory project. I intend to set them in wet concrete to secure my pier.
Thanks,
David.

[Wilso]

You can just use threaded rod and bend it where req.
Make sure you put a nut on before cutting to clear the thread of debris.
Stainless would be better.
Hope this helps!

[Dave221]

Thanks Darren, I’m considering that option but I’m wondering about the difficulty of bending half inch threaded rod.

[OzEclipse]

Heat with an oxy torch to bend

or

don't bend instead -
drill a 1/2" hole in a piece of steel or ally plate - effectively a big washer. Bolt it to the end of the threaded rod that gets set in the concrete slab.

[doppler]

You could just push the threaded rod straight into the wet concrete without bending, once the concrete sets around the thread they will never move. You would have to smash the concrete to get them out. Or get some long bolts and embed the hex head end in the concrete.

[glend]

I got mine ar Bunnings, yes they seem to have everything. They were in the area with concretng stuff like reo standoffs, in fact i found them when i was looking for individual reo bars to go inside the tube form for the pier.

[speach]

I used ramset truebolts lot easier

[Dave221]

Thanks for the suggestions everyone, much appreciated. What a great resource we have with IIS.

I did try Bunnings but they weren’t available in the ‘nuts and bolts’ section, I’ll try the ‘concreting’ section. If not, I’ll consider using straight hex bolts. I thought that would be adequate but I noticed that J bolts were suggested in most posts. I’m wondering whether the ‘washer’ option might make it a bit too difficult to push them down into the wet concrete.

If all else fails, I can always ‘Ramset’ or epoxy glue the bolts in later

Thanks again.

[doppler]

I have noticed with a lot of things to do with astro piers, everything is way over engineered for its purpose. J bolts are usually recommended for installing heavy machinery that vibrate a lot, where a normal fixing ie dynabolt would eventually move and crack the concrete.

My pier is fixed with screw in concrete anchors https://www.bunnings.com.au/ramset-12-x-100mm-galvanised-ankascrew-masonry-anchor_p2260296 . These anchor screws apparently have double the hold down capacity of dynabolts. Wet set threaded rod would be inherently stronger than a dynabolt or chemset bolt installation.

An M12 ramset bolt will hold about 400kgs in low strength 20mpa concrete and I think a solid fixed m12 bolt has a shear capacity of over 1 tonne, so multiply that by 4 and your base will support over 1000kg's.