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:
From page 113, Chapter X of "How to Keep your Volkswagen Alive" by
"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.
| _ | _ |]
Casper, der freundliche Bus
C. Robert Perring
Consultant to Technology, ATD3
Houston, Texas 77077
fax: (281) 493-5780
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