Here is the picture of the sheared cross bolt, used with EGW HD tactical rings. Nut was torqued to 65 inch-lbs., per EGW recommenations.
This bolt has, what appears to be, 10-32 threaded shank, at least this is what I was able to determine by using calipers and comparing it to the actual 10-32 screw.
It is certainly heat treated, as evident by both the appearance of the sheared area and some primitive test done with use of the file.
Anyway, doing some research on the net, I was somewhat puzzled by that 65 inch-lbs. recommendation. It seems to me, that 65 inch-lbs. is a good torque value for 1/4"-28 and similar diameter threads, which even grade 2 bolt can handle safely. But for 10-32, recoomended torque values are in the range from 20 inch-lbs. to 60 inch-lbs., depending upon the grade of the bolt, and no more than 50 inch-lbs. if threads are lubed. This crossbolt must be at least grade 8 if there is a chance for it at all to resist stress occuring at 65 inch-lbs. in static, but what about integrity of the same bolt repeatedly exposed to recoil impulse?
Any practical suggestions or opinions regarding correct torque values for 10-32 threads?
Is 65 inch-lbs. realistically a good torque value to be applied to 10-32? If not, what torque would you use?
Could you tell, by looking at the sheared area, what is the likely cause of the bolt failure?
Thank you for your input.
Boris
Borka Tools
This bolt has, what appears to be, 10-32 threaded shank, at least this is what I was able to determine by using calipers and comparing it to the actual 10-32 screw.
It is certainly heat treated, as evident by both the appearance of the sheared area and some primitive test done with use of the file.
Anyway, doing some research on the net, I was somewhat puzzled by that 65 inch-lbs. recommendation. It seems to me, that 65 inch-lbs. is a good torque value for 1/4"-28 and similar diameter threads, which even grade 2 bolt can handle safely. But for 10-32, recoomended torque values are in the range from 20 inch-lbs. to 60 inch-lbs., depending upon the grade of the bolt, and no more than 50 inch-lbs. if threads are lubed. This crossbolt must be at least grade 8 if there is a chance for it at all to resist stress occuring at 65 inch-lbs. in static, but what about integrity of the same bolt repeatedly exposed to recoil impulse?
Any practical suggestions or opinions regarding correct torque values for 10-32 threads?
Is 65 inch-lbs. realistically a good torque value to be applied to 10-32? If not, what torque would you use?
Could you tell, by looking at the sheared area, what is the likely cause of the bolt failure?
Thank you for your input.
Boris
Borka Tools
