verslagen1 wrote on 06/05/08 at 09:19:50:The only SAE bolt that fits your guidelines is a plain 3/8 Grade 8 bolt.
Available in UNC (16 tpi) and UNF (24 tpi). Please note that both are SAE spec bolts.
Cross sections for each are .0775 and .0878 sq.in. respectively.
The torque to achieve the same yield strength factor is 47 and 54 ft-lbs respectively.
So if both bolts are tightened equally to 50 ft-lbs, the 3/8-16 will be over torqued and the 3/8-24 will be under torqued. Adjusting for the difference in cross section gives a 13% drop in applied force. Varience in torque is 6%. I believe that gives the 3/8-24 a 1% advantage.
"Just the facts, maam" Sgt. Jack Webb.
Okay,, let me try again,, since I couldnt even begin to grok all that without someone sitting down, teaching for hours & all that, The question I was getting at was, IF one bolt has more threads per inch than another, then if each is torqued to the same torque, doesnt the finer threaded bolt create higher clamping forces?
Now, if I have a bolt thats, as you say, Undertorqued, then is that a problem? Will it tend to get loose? Or, is it just an ineffient use of the bolt & a manufacturer would be better off using a different bolt in an application that shouldnt be clamped so hard?
I thought I could look at the threads & recognize SAE, as opposed to what I dunno, just thot SAE bolts had a finer pitch..duhh,
Clas is open,, teach away..