Reply To: Re-bolting of “Morning Glory” at Stathams

On your figures at beginning of life a stud has five times the pull-out strength of a 40mm thread, which is only 200kg? One may wonder if after a few years the pull-out strengths might not be comparable. The attraction with glue-in machine bolts is the benign nature of the service. For almost their entire lives they sit in an unstressed state, waiting for the once in a blue moon when someone falls. Hangers are tightened up, putting an outward force on the bolt. So day and night, rain and shine, the bolt puts stress on the glue and the rock. Eventually you’d think the glue will creep, or the glue or the rock will crack a little to relieve the stress, and the hanger will be a little lose and someone will tighten it up again. This may not be true in granite. Best would be a long hex bolt with a long thread.

Modifying bolts I don’t think is a good idea. Hand roughening, the uncontrolled introduction of massive surface flaws, is one of the main objections to bashins. It’s not a fatigue situation, but the stress raisers introduced can not be good.

Standard thread is 40. Nothing much else is easily available. Although you can have anything if you order in quantity. It might be worth looking into ordering a custom lot of 100 or so. SS is expensive anyway it shouldn’t be much more. I hope. It’d be a matter of finding enough people to share out the bolts. I take it 304 would be sufficient for inland locations?

Is anyone interested in a part share of a custom lot of SS hex bolts?