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Re: threaded rod couplers

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We used to use coupling nuts all the time in structural test setups 

And I had all these same questions...luckily I had the facility to proof test the nuts depending on the loading demands to be applied. sells them (that's where I buy them) & has a good info on them as well

but a word of warning...... often coupling nuts are made from slightly smaller hex stock than "standard" nuts, thus they have a much smaller "tensile" cross section.   I actually had a couple 5/8"-11 couplers fail in tension (pretty exciting)

Mcmaster (or any good bolt supply house) has ASTM rated 2H style heavy hex couplers but they're not cheap 

Grade 8 will probably do the trick for you,  but at least from mcmaster, they're not rated & cost about the same as the 2H.

Sorry to not answer all your questions directly but I found the whole coupling nut situation kind of  a can of worms......

People use them all the time without concern as to whether  they ' will generate the full tensile design strength of the threaded rod".
They tend to think of as nuts rather than tensile members  

I know the grade 8's & the 2H's will fully develop any rod we used (A193 B7 was maximum strength rod that we use) but most of the time we could "cheap out" & use grade 5's.

In my experience only the 2H's were rated.


On Nov 29, 2007 8:47 AM, Christopher Banbury <cbanbury(--nospam--at)> wrote:

Does anyone know if threaded rod couplers, say ½" to ½", are manufactured to an ASTM standard as are bolts and nuts? What assurances are there that the couplers will generate the full tensile design strength of the threaded rod (A36, A307)? Are couplers proprietary items that require the manufacturer's certification or warranty? What grade of steel are they fabricated from?



Christopher Banbury, PE



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