During the last week of class we were given a short demonstration by our instructor on determining the highest clamping force compared with the amount of ft. lbs. used to get it there. Using the set up below, we were to test our choice of grade of bolt and put it in this 50ton jack pre-load the fastener using the jack and take the fastener to failure while recording the ft. lbs. of torque and the corresponding clamping force.
I chose to take 2 grade 5 half inch fasteners one lubed, one not and start out at 50 ft. lbs.and take each bolt and add 25 ft. lbs of torque at time until each failed.
I was able to take both the lubed and non lubed fasteners to over 125 ft. lbs. of torque and over 15,000 pounds of clamping force. The difference being that it took less ft. lbs of torque for the lubed fastener to reach a higher clamping force than the non lubed fastener. For instance at 131 ft. lbs just before failure the lubed fastener had a clamping force of nearly 17,000 lbs, where as the non lubed bolt only reached 15,350 lbs. of clamping force with over 150 ft. lbs. of torque. It was easy for me to see the point of this assignment and I enjoyed doing it. That being said, with a lubed fastener you will reach a higher clamping force with less ft. lbs. of torque applied.
Week 4
Shop Hours 17
Total Running Hours 87ish
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