Turn of Nut Installation is one of four torque-control installation methods recognized by the Research Council on Structural Connections for use on ASTM F3125 Grade A325 and Grade A490 structural hex head bolts. It generally results in more uniform bolt pretension than other torque-control methods when combined with the Pre-Installation Verification Procedure.

Pre-Installation Verification Procedure:

1. Take 3 bolts, washers, and nuts of each diameter, length, grade and production lot as they will be assembled.
2. Assemble the first bolt-washer-nut combination into the Skidmore-Wilhelm.
3. Snug the assembly using the same technique to be used in the structure.
4. Match mark the nut, bolt, and Skidmore faceplate.
5. Apply the required rotation as listed in the table below for the assembly being tested.
6. Verify that the tension on the Skidmore dial gage us at least 5% more than the min. bolt pretension listed in table to right.
7. Record the tension achieved in a log book.
8. Remove the assembly and repeat steps 2 through 7 until three assemblies have been tested.

Turn-of-Nut Method (Flat Surfaces under Bolt Head and Nut)

Snug tighten the bolts in the joint, match-mark the nut and protruding end of bolt and rotate the nut by the proper amount listed in the table below.