Find how much a bolt or stud stretches at a target stress or load. Use it to set elongation targets when you verify bolt load by measurement rather than torque. Values are for reference; confirm against the current edition of the governing standard. Send us your bolting list for a quote or call (281) 581-0176.
Related: Bolt Stretch and Elongation Chart · Thread Data for Bolting Sizes · All technical docs
Method
PCC-1 J-3 uses an effective length equal to the distance between the mid-thicknesses of the nuts. With a heavy hex nut taken as one diameter thick, that is the grip plus 1D. For a stud in a tapped hole, half a diameter of the threaded-in portion is counted, which also gives grip plus 1D. Elongation is ΔL = Sb × Leff / E.
Measuring
- Use an instrument that reads to 0.001 in. and is calibrated (J-3.3).
- Take final readings after all tightening passes are complete.
- Use the change between two states (before and after loading), not a single reading.
- Ultrasonic and micrometer readings need temperature compensation.
- Results are only valid while the bolt stays below yield.
References: ASME PCC-1-2026, Guidelines for Pressure Boundary Bolted Flange Joint Assembly. Summaries are paraphrased; clause numbers refer to ASME PCC-1-2026 unless noted. Patriot Bolt manufactures bolting and does not perform bolting, training or joint assembly services.