Help bolting together 1/8" steel

[woodlandfarms]

Looking for thoughts here...

I am putting a lid on a tank, the lid must seal shut and will have some sort of gasket material to keep it leak free.

So the question, as it is only 1/8" thick, do I use self tapping screws or do I use 1/4" bolts and tap the threads out. Is there enough meat for a 1/4" which I would rather use.

At this point there is no way for me to weld a nut onto the bottom of this, although I am going to look and see again.

 

[Mendonsy]

The rule of thumb is that you need at least enough metal thickness for 3 full threads. With a regular 1/4-20 you would only get about 2-1/2 threads. 1/4-28 or 12-24 would work.

 

[PILOON]

You can always use 'riv-nuts', they are inserted with a compression tool and sell in 6,8,10 X 32 and also 1/4" threads.
They are sort of like a pop rivet but with a threaded center.

 

[4get gto]

∆ What PILOON said. They work very good.

 

[flyerdan]

Riv-nuts would be the way to go unless the tank will be completely full, then there might be a little seepage past the threads. In that case, you might need splined studs, like small scale lug bolts that can be put in from the bottom up and sealed.

 

[kencunningham]

Is the hole round or square or rectangular? if it is anything but round you could weld the nuts on the lid and then bolt it to the inside of the tank. Of course that would be welding the nuts to the lid.

 

[CADplans]

#10-32 self tapping screws!!

Put them a little closer,,, :thumbsup:

 

[flyerdan]

I've made nut plates before by welding nuts to thin flat strip, 16ga. or so, and plug welding it so it's inside a square or rectangular tube, the same principle could be used for the inside of a tank where you can't get to the inside to weld, as long as making the plug weld from the top is doable.

 

[woodlandfarms]

Thanks everyone. I went with 1/4 28 and that will do the trick. I was very close to using self tapping but I found the 28 thread at the store and changed out at the last moment. It is holding well.

 

[mcfarmall]

Riv nuts or stud welder.