STA and doubles standard bolt size?

[JessH]

I just got an Agir Brokk STA and the bolts that are built into it are too big to fit in the holes on my Hammerhead backplate. So this made me wonder, what size bolts are "Standard"?

I am thinking this may be a metric/standard issue. Damn europeans.

I am thinking I will just drill out the square holes on my bp to be slightly larger. Anyone see any problem with doing this?

~Jess

 

[Gil57usa]

Do whatever works for you. The bolts on my Doubles sets are 5/16"

 

[JeffG]

I am thinking I will just drill out the square holes on my bp to be slightly larger. Anyone see any problem with doing this?

~Jess

Square holes? I would say its your BP thats unstandard. Drill them out, you would have to anyways if you went to doubles.

 

[rjack321]

Highland bands use 3/8" bolts for smaller tanks and 5/16" with larger tanks.

Square holes would be non-standard. I would drill them out to 3/8" - assuming that the STA doesn't use something even larger!

 

[The Horn]

Your BP is probably designed to take a stainless Carriage bolt. These have the round head with a square section followed by the threads. If you purchased the proper size carriage bolt you may find the nice round head at your back more appealing

 

[JeffG]

Your BP is probably designed to take a stainless Carriage bolt. These have the round head with a square section followed by the threads. If you purchased the proper size carriage bolt you may find the nice round head at your back more appealing

Doesn't help for doubles though.

 

[kidspot]

or an STA as the protruding end would unseat the tank, unless you could get it real close to flush.

I've seen a number of BP's with square holes, but as mentioned 3/8 and 5/16 are the 2 standard sizes used in bolts, sounds like Hammerhead assumed the smaller (5/16) would be used with their plates.

Drill it out

 

[CIBDiving]

The 'Standard' bolt size was 5/16", in recent years 3/8" has become more common.
I don't know Why some started putting square holes on the plate! It's of no use at all, on modern designs. But the STA in early forms had more space between it and the tank. That let you reverse the bolts and use a carrige bolt from the plate side.
Idealy, The STA should have the square holes not the plate.

JessH - you've got the right Idea, just drill the holes to fit. It'll make no real difference.
Time was when the QC of the plate makers was so bad that it was common to have to 'move' the holes a mm or 2.

 

[JessH]

Thanks for the input! The drill is coming out. I just checked and the Agir-Brokk STA is using 3/8", so I guess the hammerhead stuff is 5/16".

On another note I am thinking about taking some JB Weld to my Hammerhead 2 piece STA and bolts. It comes with perfectly countersunk screw head bolts but you can't really tighten them down too well without getting in there with a screwdriver. They have never come loose on me but I am really liking the fact that the agir-brokk STA bolts are threaded into it.

~Jess

 

[Quaff King]

"The Horn" is correct on the square hole answer. The benefit of using a carriage bolt is that the bolt has a square shoulder that drops down into the square hole. Thus no tool is required to tighten the wingnut. They also wedge in nicely with the tap of hammer so you don't have to hold them from the other side when installing.
It sounds strange but I've used round bolts in square holes for years with no problem whatsoever. I don't dive doubles however so that could cause some other issues.