Assuming you are talking about crank bolts holding a crank onto a square taper spindle, I (unhelpfully) find that a normal 14mm socket (from a normal socket set) fits a bolt which has a hexagonal head. The diameter of the space to get the socket in is >18mm.
If the spindle is of the type (likely 30+ years old) that has a protruding threaded boss then the nut will normally be a 14mm nut (and unscrewed the same way).
Sheldon worth a quick scan:
https://sheldonbrown.com/tooltips/cotterless.html https://sheldonbrown.com/bbtaper.html
Most crank bolts 'nowadays' are undone with a ?6mm allen key.
Why do you feel the need to use a torque wrench? The spindle is steel; the cranks are robust Al alloy. The bolt just needs to be 'tight' (so tighten it, hit the crank with a rubber mallet and tighten it again: job done.
In use, because the interface has that taper, the crank will squirm up the taper till it can't. You should not regularly tighten the bolt: zero need. If you do there's a risk of damaging the crank.