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Bolt failure in the UK 1-Jun-2013 At 1:16:50 PM Robbie

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Oils aint Oils

Fastener Application Scenarios
1. Bolts that attach a D-ring tow bracket to the bumper face (Think Hummer and Big Chrome Bumper Shackles) of a motor vehicle would be critical under tension. So you would want to know that the tensile strength of the particular set of bolts is suitable. For example, think a snatch strap being tensioned under super dynamic loading, and you are the tow vehicle. The possible chain of events: (1) Tension, (2) Bolt failure, (3) missile launch, (4) terminal velocity, (5) impact. “Got the picture.”
2. Bolts that attach winch-mounting plates are typically seeing mostly shear loads thus preventing the winch from departing from the motor vehicle during winching operations. In that case, shear strength is important.

Fastener Grades. There are different types of strengths listed for each grade.
• Proof strength (about 90% of yield), ultimate tensile strength (bolt fails in stretch)
• Yield strength (bolt begins to get a permanent set and changes crossectional area typically)
• Shear strength (bolt prevents parts from separating by using its shank or body as a stop).

So, depending on how you are using a fastener, you would look at the appropriate and corresponding strength type needed. Wouldn’t you?

Ponder this one as you approach you next clip on a climb at your favorite crag. As you know the strength rating of the crabs on the quickdraw you are about to use? If you don’t have a look at the spine of one of the carrabiners, now have a look at the head of the bolt\nut of the fastener you are about to clip, the one with the hexagonal thingy! If you can just reach for the check list in the chalk bag. (And breathe) “Now, which grade of bolt is that?” “Watch me…………..”

Check out the following links for a broader technical view.

http://www.dot.state.il.us/materials/fasteneridentificationguide.pdf

http://www.tmr.qld.gov.au/~/media/busind/techstdpubs/Technical%20notes/TN62assemblytensioninghighstrengthboltsnuts.pdf

Safe climbing :-)