Break Away Torque, HOw to calculate |
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Break Away Torque, HOw to calculate |
Brett W |
Mar 26 2006, 11:44 PM
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#1
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Advanced Member Group: Members Posts: 2,856 Joined: 17-September 03 From: huntsville, al Member No.: 1,169 Region Association: None |
We all know that the torque needed to loosen a fastener is usually higher than the torque at which the fastner is tightened. Is there a way to calculate this number.
I just got a new 3/8 Impact wrench and was doing some test with it. We torqued a 1in course thread bolt to 250 ft-lbs. Then used this impact to break it loose. It did it with no problems at 175 psi. Couldn't touch it at 90psi. ANy body know how to calculate that torque? |
Brett W |
Mar 26 2006, 11:56 PM
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#2
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Advanced Member Group: Members Posts: 2,856 Joined: 17-September 03 From: huntsville, al Member No.: 1,169 Region Association: None |
That's what we figured. We oiled the bolt and welded the head to a piece of steel tubing to keep it from moving. Then we put a 2in 1.25x.125 tube between the head of the bolt and the nut. When we finished testing a 3/8 gun, a 1/2in gun and a 3/4 gun, we had mushroomed the piece of tubing.
The manufacture says the little gun will pull 300ft-lbs in reverse (at 90psi, BS). But is does pull a bolt loose that has been torqued to 250lbs. It is the biggest torque wrench I had tonight. I am going to get ahold of a 3/4 torque wrench that should do at least 400ftlbs. Anyway I am trying to figure out if how much higher the break away torque is than the measured torque. |
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