[TowerTalk] Stainless Bolts and Nuts on Tower

Bob Perring perring@texas.net
Fri, 12 Nov 1999 07:53:09 -0600

As but a few examples:
For 316 SS bolts in the sizes of : 1/4", 5/16", 3/8".

Tightening to 65% of yield strength on the above sizes,
using a 316 SS bolt, SA-193 Grade B8M, Class1,
with bolts having a yield strength value of 30,000 lb/ sq. in.,
with a nickel based anti-seize compound being used on the fasteners:

With a torque wrench:
Use 2 ft-lb on 1/4-20UNC bolts and nuts
Use 4 ft-lb on 5/16-18UNC bolts and nuts
Use 8 ft-lb on 3/8-16UNC bolts and nuts

If tightening dry, go to 5,9,17 ft-lb, respectively.

Those are the values I use on offshore oil platforms.
The low number always surprises people.
We just about always tend to over tighten.

Without a torque wrench:
Do This...............

 From page 113, Chapter X of "How to Keep your Volkswagen Alive" by 
John Muir.
"A Manual of Step by Step Procedures for the Compleat Idiot"

"OK, If you have or can borrow a torque wrench, no sweat, just torque 
the bolt to 9 ft. lbs. If you don't have a torque wrench, try this: 
It's kinda like bunting in baseball when you choke the bat. Choke the 
wrench by holding it and applying the turning force 6" (half a foot) 
from the center of the bolt. Now you can guess how much force is 18 
pounds. Apply just that much at the 6" point and the torque will be 
right - at least as right as you guess about the 18 pounds. Set a 
bathroom scale up on its side and practice pushing 18 pounds."

Better yet, a 3/8" drive click style torque wrench (+ 4% accuracy) is 
about $20.00 from Northern Tools in their latest catalogue.
The flex handle style torque wrenches are even cheaper, and available 
at most automotive supply stores.

Bob, N5RP
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Home of:
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C. Robert Perring
Consultant to Technology, ATD3
12715 Westmere
Houston, Texas 77077
tele:(281) 493-5780
fax: (281) 493-5780

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