Standard DTI FAQs
Breaking bolts during installation
-
You break some bolts before their DTI's have been compressed sufficiently
- You try your best but it appears too difficult to properly compress
the DTI bumps, even though the ironworkers sit on the bolts for 20,
30, or more seconds: See Bolt threads damaged.
- How much torque does it take to tension a bolt with a DTI? See Torque
Control
- You notice that the DTI seems to compress all the way to flat on one side, but still leaves a gap greater than the thickness of the feeler gage on the other side. Is this OK? See Flattening DTI's
1.You break some bolts before their DTI's have been compressed sufficiently
Breaking some bolts during the installtion process is normal; say, less than 1 percent. Breaking more than this number may mean there is a problem. When this occurs, it means the bolt has broken at a tension lower than what is needed, and probably that the bolt lubricant has deteriorated.This happens occasionally and is usually easily correctable. It occurs because the torsional stresses within the bolt have acted to combine with the tension stresses to cause a combined stress failure at a tension less than that required to compress the DTI. Remember, DTI's ONLY measure tension, not torque.
The solution is to reduce the torsional stress by lubricating the bolt threads and/or the face of the nut that is turning against the washer surface. This can be done by using any lubricant available, or by using a stick wax product that Applied Bolting sells.
Breaking of the bolt by torque build up is rarely accompanied by some "necking" or stretching of the first few threads. The fracture surface is characterized by a spiral surface.
