The worst thing posible is people overtightening things and 250
foot pound of torque is definitely in this
category. The lug nuts on a typial car wheel only use 95
foot pound, many of the suspension bolts on a car suspension are less than 100
foot pound. In fact the
hub nut on the drive axle is usually 145
foot pound or less. All of these fastners have to cope with both
dynamic, static and vibration loads which are significantly greater than anything a
stage light is likely to experience.
By the way has anyone thought of the
safety issue when overtightening fastners and someone slips while attempting to unfasten one of these fastners or worse has to nresort to a cheater pipe on the end of the wrench. Has anyone actually undone a fastner torqued to 250
foot pound - I have and you usually need an air impact gun, an
electric impact gun or a 24 inch
breaker bar. You will not undo a fastner at this torque
level using a six inch, eight inch or ten inch
crescent wrench.
As has been mentioned numerous times above - finger tight plus a quarter or half turn is all that is required.
This thread started out debating the merits of
C clamp rating and has explored the important issue of how tight the fastner should be that locks the clamp to the pipe but has got lost somewhere along the way. Remembering that a lot of inexperienced people read this forum we should avoid some of the more esoteric stuff.
Before we get too hung up on
rating of c clamps we should also remember that much of what is hung above is not rated - I know no manufacturer provides a
rating for
yolk on the
fixture and none of the fixtures are made from structural steel or 6061 aluminium and none of the bolts on the locking mechanisim are Grade 9. If we are not careful we will identify perceived risks in everything at a
level that is unwaranted.