Tyrell Corp wrote: I'll keep doing my #6 bolts by feel.
Steve
Listen to the man, I read this shit daily on Lotus and Ferrari forums, old stretched high tensile bolts in cast ally+ innacurate tourque wreches = lots of forum postings and helicoil/timeset/tig repairs.
Learn by our mistakes
Not everyone has the "feel"....
When I was the toolmaker and designer for a large electronics company, I once sourced an electric / electronic torque limiting screwdriver for $40 000...
each, and that was the low quote. Highest was $62 500. Why was such an expensive high tech tool necessary in the first place - simple: the people that worked there could not reliably tighten the screws with any kind of consistency or reliability, and it was costing much more than just money. That was a special application, and in the end we cut back our "needs" list until the price came down to $12 000 each, and I had to further modify each tool myself before commissioning them on the line.
Previously, despite my warnings, the chief design engineer on that project had a bad habit of specifying the torque on various critical fasteners as "hand tight" or "finger tight". One day, after receiving the umpteenth e-mailed customer complaint on the over 90% failure rate of the product, I had that engineer come down to see his production line in person. I lined up two assembly workers from the same line to tighten his fasteners "hand tight", one an 85 lbs. 18 year old Asian girl, the other a 290 lbs. former college football line backer...there was some variance....one fell apart before reaching the next process, the other had bent and broken components.
Following that demonstration, and forwarding some of his B.S. engineering skills e-mails to his superiors, two improvements were made - all product engineers had to meet with the production line managers and supervisors at least once a month and spend an hour on the production line, and all references to "hand tight" or "finger tight" - actually anything other than a # torque specification - were stricken from the company's work instructions....and I gradually stopped receiving those e-mails...