All About Fasteners, Episode 7: How ITW tests its fasteners, Part 1 (VIDEO)
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VideosTechnical specialist Andrea Galindo of ITW shows Rob Koci how the firm tests the tensile strength of its fasteners.
In this video, research engineer Andrea Galindo demonstrates how ITW tests the tensile strength of its fasteners.
The tensile (“pulling”) strength of a piece of a fastener can be expressed as two values. First, there is the allowable load – which is what the fastener is rated at. Then there is the ultimate tensile strength – which is the mean (average) load under which the material will fail.
Here, Andrea demonstrates a test of a 3/8″ x 4″ RSS GRK screw. This fastener has an allowable load of 1,914 lbs. It has an ultimate tensile strength of 5,824 lbs. You can see that the safety margin that is built into fasteners – GRK ones in this instance – is actually quite large. This fastener will only fail at about three times its load rating. But then, that’s typical of engineering safety margins since the beginnings of the modern world. We don’t build for common loads, or even uncommon ones. We build – where possible – for extraordinary ones. And so should you.
This video was shot at ITW’s test facility in Toronto.
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Glad to see the 300% safety factor is observed. I’d like to see a fastener head torque failure test with a comparison to a number of different types of fasteners. e.g. drywall screws vs. regular screws, vs GRK, vs class 8 bolts or similar.
Also, as I use it a lot, I think it would be interesting to do failure tests on rope and chain. Too many times I’ve seen people rigging with dog chain and then applying thousands of pounds of force with the obvious results.