ROTATIONAL CAPACITY TEST – SHORT BOLT PROCEDURE

For bolts too short to fit in a tension measuring device

(Adapted from ASTM F3125-23, Appendix 2)

SCOPE

This IM provides the test procedure for determining the Rotational Capacity of bolt assemblies too short to test using a bolt tension measuring device. The Rotational Capacity (RC) Test for all high strength fasteners shall be performed in the shop and in the field as required by Standard Specification 2408.03, S.

EQUIPMENT REQUIRED

· Calibrated manual torque wrench. When tested torque values from Step 5 are expected to exceed 600 ft.-lbs., a torque multiplier may be used in conjunction with the calibrated torque wrench, subject to the approval of the District Materials Engineer. Calibration of the torque wrench shall be verified by an approved testing agency at intervals not exceeding 12 months. Furnish the current calibration certificate with the torque wrench.

· Assortment of bolt spacers, to be placed within the grip of the fastener as necessary to position the nut at the proper location for testing. The bolt spacers must be of appropriate material type (steel or equivalent), thickness, hole diameter and cross-sectional area to permit full tightening of the bolt in accordance with the test procedure, without bending or damaging the test washer, bolt spacers or steel test section. Unless otherwise approved by the District Materials Engineer, the hole diameter of the bolt spacers shall not exceed the hole diameter of the test washer, and the cross-sectional area of the bolt spacers shall not be less than the cross-sectional area of the test washer.

· Rigid steel test section with a round, standard size hole to be used as the test hole for the inspection torque determination procedure. The geometry of the test hole shall be consistent with the requirements of Standard Specification 2408.03, S, 5, a, 1). The steel test section shall be adequately secured and stabilized to prevent displacement during testing. At the contractor’s option, an accessible and appropriately sized hole in the work (girder splice or crossframe connection, etc.) may be used as the test section.

PROCEDURE

A minimum of two representative fastener assemblies, from each rotational capacity test lot, shall be tested for rotational capacity in accordance with Standard Specification 2408.03, S, 4, a. The following procedure shall be applied to each individual fastener tested for rotational capacity.

1. Obtain one representative fastener assembly, consisting of a bolt, nut, and washer, from the rotational capacity lot. Report the production lot numbers each for the bolt, nut, and washer components, as furnished by the manufacturer of the individual components. Report the rotational capacity lot number associated with the combined fastener assembly, as furnished by the supplier, in accordance with IM 453.06B. Report the date of testing, and assign a unique test number for each rotational capacity test (example: Lot##Test##).

2. Install the fastener assembly in the test hole. When installed properly to finger-tight condition, bolt stick-out shall be at least flush with the nut, but not greater than 3 complete threads of stick-out past of the nut. This will typically provide 3 to 5 complete threads within the grip of the fastener. The washer from the rotational capacity lot (test washer) must be in direct contact with the nut. Up to 4 additional washers and/or approved bolt spacers may be used between the test washer and the face of the steel test section, to establish proper positioning of the nut.

3. Using the calibrated torque wrench, tighten the nut to a torque value within the Snug Torque Range indicated in Table 392-A. Report actual measured snug torque achieved. Torque must be read with the nut in motion.

Table 392-A: Snug Torque Range
Bolt Diameter (in.)	¹/₂	⁵/₈	³/₄	⁷/₈	1	1 ¹/₈	1 ¹/₄	1 ³/₈	1 ¹/₂
Minimum Torque (ft.-lbs.)	15	29	50	82	123	173	245	321	425
Maximum Torque (ft.-lbs.)	30	58	100	164	246	346	490	642	850

4. Match mark the bolt tip, nut, and the steel test section in a straight line.

5. Using the calibrated manual torque wrench, tighten the nut by rotating an amount as close as possible to, but not less than, the Minimum Service Rotation indicated in Table 392-B. The rotation is measured from the match marking from Step 4. A second wrench must be used to prevent rotation of the bolt head during tightening. Record the torque value required to achieve the Minimum Service Rotation. Torque must be read with the nut in motion. If actual rotation exceeds the Minimum Service Rotation, record the actual service rotation to the nearest 1/6 rotation (1/6 rotation = 60° = 1 flat).

Best Practice for Dial-Type Torque Wrenches - Read and record the torque when the Minimum Service Rotation is achieved.

Best Practice for Click-Type Torque Wrenches - Set the torque wrench to click at a torque value that slightly exceeds the expected torque needed to tighten the assembly to the Minimum Service Rotation. If the torque wrench clicks before the Minimum Service Rotation is achieved, reset the torque wrench to a higher torque setting and resume tightening until the Minimum Service Rotation is achieved. Record the lowest torque setting that causes the wrench to click (nut in motion) after the Minimum Service Rotation has been achieved.

Table 392-B: Minimum Service Rotation

Bolt Length

4x bolt diameter

or less

More than 4x, but no more than 8x bolt diameter

Rotation (turns)

¹/₃

¹/₂

6. Compare the torque recorded in Step 5 with the Maximum Allowable Torque at Service Rotation from Table 392-C. Assemblies fail the test if the recorded torque from Step 5 exceeds the Maximum Allowable Torque at Service Rotation.

Table 392-C: Maximum Allowable Torque at Service Rotation
Bolt Diam. (in.)	¹/₂	⁵/₈	³/₄	⁷/₈	1	1 ¹/₈	1 ¹/₄	1 ³/₈	1 ¹/₂
Maximum Torque (ft.-lbs.)	150	290	500	820	1230	1730	2450	3210	4250

7. Further tighten the nut to achieve a total rotation as close as possible to, but not less than, the Full Test Rotation indicated in Table 392-D. The total rotation is measured from the initial match marking from Step 4. Assemblies that strip or fracture prior to this rotation fail the test.

Table 392-D: Full Test Rotation

Bolt Length

4x bolt diameter

or less

More than 4x, but no more than 8x bolt diameter

Rotation (turns)

²/₃

8. Loosen and remove the fastener assembly from the test hole. Inspect the nut and bolt for signs of visible damage. Rethread the nut on the bolt. Assemblies which do not accommodate turning of the nut by hand, from the tip of the bolt to the position the nut was in during the test, fail the test (nut does not need to thread past the position it was in during the test). Assemblies which show signs of thread failure, stripping, or torsional failure fail the test. Fractured or broken bolts fail the test.