When tightening the 5/16" carriage bolts on the end bearing of my bedroom slide motor they broke off. I had my torque wrench set to 19ft. lbs. as per the TSB but this was obviously too much. So I looked up the bolt torque tables and 19ft. lbs. only works for Grade 8 bolts. The bolts I have are 307A and should be tightened to 66 in. lbs. So if anyone else is tackling this job make sure you check the end markings on the bolt and use the correct torque for that bolt.
Here is the link to the
chart if you want more details.