Standard DTI FAQs
Turning Bolt Head Against DTI Bumps
If you must turn the bolt head AND put the DTI under the bolt head, it is advisable to place a hardened flat ASTM F436 washer between the bolt head and the DTI bumps so the action of turning the bolt head does not grind down the DTI bumps instead of evenly compressing them.
However, it is possible to turn the bolt head DIRECTLY against the DTI bumps in some situations, especially if the tightening is to be done by hand, and if the procedure is calibrated first. The proof is to just try it in a Skidmore and see if the DTI reacts correctly. If it does, go to it. If not, put a flat washer in between.