Ed Haman of Providence Bolting Technologies (Baytown, TX.) has done a lot of work and research in this area. I have seen some seminars he has conducted with fitters. He is a big proponent of utilizing some technology (any technology) when bolting. I have seen him demonstrate with a class divided into sections that those employing torque wrenches achieve more accurate and uniformly tight bolts than those who use "feel". But I have also seen him demonstrate that those employing torque wrenches at least some of the time achieve more accurate and uniformly tight bolts when they are not using torque wrenches than those who never employ them.
I think we're talking about the same thing but from two different angles.
Employing technology to tighten bolts is better than not employing it. And employing it some of the time is better than never employing it.
>>> Christopher Wright <chrisw@skypoint.com> 03/27/02 09:09AM >>>
>torquing is more of an art than science.
Too true
The NASA Fastener Manual shows preload accuracies as follows
'Feel' ±35%
Torque wrench ±25%
Turn of the nut ±15%
Load indicating washers ±10%
Fastener elongation ±3-5%
Turn of the nut and load indicating washers are accurate but only for 'standard' installations, like buildings or machinery. With soft gaskets you don't know for sure how many turns provide the right preload, so you're back to 'feel.' Probably good fitters with specific experience in a given installation can do better than 35%. If it were me I'd be inclined to figure out what torque I needed then discuss it with the best fitter I could find and adjust accordingly.
Christopher Wright P.E. |"They couldn't hit an elephant from chrisw@skypoint.com | this distance" (last words of Gen. ___________________________| John Sedgwick, Spotsylvania 1864)http://www.skypoint.com/~chrisw
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Wed Mar 27 10:06:00 2002
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