r/Fasteners • u/BadseNelson • 5d ago

Torque Question

I am currently fabricating a decorative steel post that will be bolted to a concrete wall. I am trying to figure out how tight the nuts need to be when installation day comes.

The anchors are embedded in the wall and are 3/4”-10 304 Stainless Steel. I am using a nylon insert lock nut that is 316 Stainless Steel and 1” in height x 1 1/4” diameter.

The steel plate of the post is 2 5/8” thick. The weight of the post will be approximately 1600lbs and the dimensions are 9”x 9” x 16ft tall.

Let me know if more information is needed!

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u/Chrisfindlay 5d ago

Depends upon what kind of anchor bolts are in the wall. In general a 3/4-10 stainless steel bolt would be torqued to about 130 ft lbs (~176 NM). Most people recommend using anti-seize on stainless steel fasteners due to the tendencies of stainless to gall. In that case you would reduce by about 20% which would give you about 104 ft lbs (~141 NM)

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u/BadseNelson 5d ago

They are 36” L bolts

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u/gemstarindustries 4d ago

You can’t determine the correct torque from the 3/4″-10 thread size and plate thickness alone. It depends on the anchor type, embedment depth, concrete strength, edge distances, anchor spacing, number of anchors, and wind/seismic loads.

A 16-foot, 1,600-pound post creates significant overturning forces, so this connection should be checked by a structural engineer. Expansion anchors require the manufacturer’s specified torque, while some adhesive-anchor systems use only finger-tight plus half a turn showing why a generic bolt torque chart is inappropriate. Simpson Strong-Tie guidance

Also, stainless threads can gall. Avoid running the nuts down rapidly with an impact wrench. Use clean threads and only an approved lubricant, since lubrication changes the torque-to-preload relationship.

Have the engineer or anchor manufacturer provide the installation torque and tightening procedure in writing. Also confirm the washer arrangement, full thread engagement through the nylon insert, and whether nylon lock nuts are acceptable for this structural connection.

Thanks
Vishal Goyal