4.7 mm front brake nut thread engagement enough?
I've got dual-pivot caliper brakes on a vintage fork with non-recessed mounting. My brake nut is a nylock. The total depth of the nut from crown to base is 7.7 mm. A depth gauge tells me that when fully tightened up, I've got 4.7 mm of nut thread engaged with the mounting bolt. Of the total nut depth, a good 1.5 mm at the crown is taken up by the nylon bushing, so I estimate a total threaded depth to be 6.2 mm. Is engaging 4.7 mm of the threads enough for front-brake safety? I saw various articles online written about modern-style forks with recessed mounting nuts indicating a minimum of 10 mm of thread engagement. That is 3.8 more than I would have available to me if the nut threaded farther onto the brake stud than it does, and 5.3 mm more than what I can achieve (fork-crown-brake-stud-mounted front light at the front of the fork, fender tab and fender washer at back side). I would rather not drill out the fork to take a recessed nut. Does anybody know the common standard for a vintage non-recessed fork and vintage fastening nut? Average thread depth engagement? I sure would hate to lose my front brake at speed.