I did some research into how tight an expansion bolt should be set (which is 25 Nm for an M10 Hilti expansion bolt HSA-R), and what happens if you go off the specifications
. As a mechanical engineer, I find this is quite fascinating (and yes, I know glue-ins don't have this problem). Best literature I could find on this topic:Delhomme, F., Pallud, B. and Rouane, N., 2018. Tightening Torque Influence on Pullout Behavior of Post-installed Expansion Anchors. KSCE Journal of Civil Engineering, 22(10), pp.3931-3939. https://link.springer.com/article/10.10 ... 018-0930-9
Due to copyright, I can't share the PDF version, but at least go read the abstract.
I was quite paranoid about the spec and got a torque wrench that I use for bolting to ensure perfectly set bolts. Now that I am used to the feeling of how much torque is needed, I might as well use a normal spanner (and after reading the paper). One key finding is that for the range of 50% to 180% of recommended setting torque, the bolt rupture mode might change at failure (the way it breaks), but not really the max applied force before failure (when it breaks). This means there is likely a decent amount of tolerance on the spec as a safety factor.
Keep safe and keep climbing!
