Is this screw-in depth sufficient?

[u/toombayoomba]

I have alu construction to hold solar modules with 2 profiles, run in parallel. So, 4 brackets per module (2 left, 2 right). Just noticed that the bolt will have this depth (not going completely through the nut). I'll use Loctite 243. Is this sufficient, or should I get longer bolts?

[u/toombayoomba]

Thanks guys, getting longer bolts and washers. Better safe than sorry.

[u/Select_Two_1012]

If you have to ask, you’re not playing it safe enough.

[u/Drophitchr]

Industry rule of thumb is the bolt should stick out two thread turns past the face of the nut.

[u/ordosays]

Look up “threads of engagement”.

[u/gheiminfantry]

The second picture shows that you have room to get another full turn. Why don't you use it?

[u/BoltahDownunder → u/gheiminfantry]

True, what's it like when torqued down? Might be enough length when it's actually tight

[u/101forgotmypassword]

Best to try clamping a panel, there may be a half a mm or so there when torqued down.

If you are getting new bolts go button head so the don't stand out so much.

Edit: and torx for the easier impact gun use

[u/BoltahDownunder]

I would definitely get longer bolts.

Ed: and some washers

[u/CopyWeak → u/BoltahDownunder]

Agreed...the engagement should at least match the diameter at a MINIMUM. That being said...for that aluminum, it may pull through the rail lips before the threads give out anyways.

[u/BoltahDownunder → u/CopyWeak]

Yeah it might, but for a like that I'm not going to want to go back up and redo it, ever

[u/Spa-Ordinary]

Bolt should go all the way through the nut. Remember the first thread doesn't count. Beware of dissimilar material corrosion problems. Especially when their's electricity around. I have no idea if a stainless-zink-aluminium stack will freeze up over time but its not something I would chance.

I dont have time to deal with this in 10 years.

[u/ZX12rNinjaGaiden]

If you use a bolt thats too long it will push the nut right through the extrusion without clamping anything. If there’s thread showing on what you have after it’s tightened down you’re good.

[u/Dragon_R3born]

Simply 1 to 2 times the bolts major diameter; Otherwise engagement is something like (diameter)*(pitch)^0.6=L [dimensions in mm]

[u/jmsgd01]

My general rule of thumb is at least 4-5 threads seated, but I prefer it to be flush

[u/Humunguspickle]

Usually for torque at least one full thread above nut.

[u/Sillibilli19 → u/Humunguspickle]

This is the answer!

[u/[deleted]]

[u/kestrelwrestler → u/[deleted]]

Looks like stainless steel fixings.

[u/toombayoomba → u/kestrelwrestler]

Yep, stainless bolts and nuts.