A mechanic states, “12.36 hours after installing (this particular) through-bolt and torquing it to specifications— the bolt broke (P/N SA641931-10.75; Lot/N B05006996). (This) totals five broken bolts on three different engine models.” (Unfortunately, the applied torque for a given application was not provided.

Original bolt specifications and their comparison to bench-test results of a couple of new and used bolts would have been very telling. One can increase the “validity” of any concern by describing frequency and method of instrument calibration, and degree of sample control. A necessary condition of validity is “reliability”. Reliability improves for any concern by increasing the number of measures. At what torque values do brand “X” and “Y” fail? How many times out of five tests, does each succeed or fail? Finally, include contact information. Your measures have to be repeatable by others, further increasing “reliability.”

Perhaps other mechanics that have experience with these bolts will provide additional detail. See the attached picture.)    

Part Total Time: 12.36 hours.