Correct torque for grade A rod ?

[xtal01]

Hello,

I posted this in the structural area but maybe it is more correctly a mechanical question so I am posting here also.

I have looked all over the web for a chart showing the correct torque for nuts on a threaded rod.

Found lots of charts but values all over the place.

The issue might be the material.

The threaded rod is 1/2"-13 hot dip galvanized grade A

So, this is the lowest strength rod available.

I definitely don't want to over torque it.

Galvanized rods seem to have a higher ft lb torque rating.

Can someone tell me the value or point me to a chart with the correct torques for nuts on this rod?

Here is a link to the rod (bought at Zoro) Link

Thanks .... Mike

 

[xtal01]

Just tried 5 ... they all held.

I realized that it might be pointless finding a value ... I am using a Harbor Freight torque wrench .. probably off by 100%

I set a 3/8 drive to 25 ft lbs .... I think I am double that. The washer pulled into the 2 x 6 before it "clicked".

I am using lock washers and large washers.

I am sure it will be fine for what I am doing.

I used AC100+ Gold

I followed the instructions including blowing out and mechanically brushing the hole.

Must have done something right ... the first 5 held.

Mike

 

[desertfox]

Hi xtal01

The torque for any joint is dependant on the materials being clamped. The values for various grades of nut and bolt, screwed rod etc are maximum values for the fastener’s themselves and not necessarily for the materials being clamped. If the material being clamped doesn’t have the same strength of the fasteners then it’s likely the joint will be over tightened and t.he material being clamped will be over stressed and probably yield and over a short period of time the joint may well fail or come loose. What exactly are you clamping and what.s the configuration of the joint?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[xtal01]

I was just clamping a pressure treated 2 x 6 to a concrete pad ... nothing fancy.

And you are right ... even at 25 ft lb (at least that is what my cheap Harbor Freight torque wrench was set at) the washer (I used a slightly larger 1 1/2" flat with a lock washer on top) is pulling into the wood.

I can even see as the boards dry out, the nut will have less tension on it.

I know this is how houses are built ... and you can't get into the walls to tighten them.

In my case, not critical but it just makes me wonder how well tied down most houses are.

Thanks ... Mike

 

[EdStainless]

Forget the lock washer, it is less than useless.
Since the wood is softer you really should be using a thick flat washer so that it minimizes the cupping of the washer.

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P.E. Metallurgy, consulting work welcomed