The Thread Elongation Gauge is a precision tool designed to detect plastic deformation in bolt threads caused by excessive tension, temperature fluctuations, or dynamic loading. It measures elongation in the central threaded section and provides both a percentage value and a clear pass/fail indication.

All gauges are manufactured in accordance with ASME and DIN standards, ensuring reliable assessment of bolt integrity. For standard-grade bolts and nuts up to M30 (1 inch) in diameter, replacement is recommended when hydraulic torque wrenches or tensioning tools are required.

For larger diameters, the decision should balance the cost of cleaning, deburring, and reconditioning against the cost of replacement, especially for critical flange assemblies.

The gauge is based on the 0.2% yield strength (proof stress) criterion—indicating the onset of plastic deformation. While some organizations use 0.1% or 0.5%, the 0.2% standard remains the most practical and technically sound.

Note: Some companies apply a non-standard rejection criterion of 2% elongation, which significantly exceeds the conventional 0.2% yield-based threshold and is considered technically unjustified.

Thread form according to Unified Inch Screw Threads ASME B1.1

  • 4 threads per inch

  • 4.5 threads per inch

  • 5 threads per inch

  • 6 threads per inch

  • 7 threads per inch

  • 8 threads per inch

  • 9 threads per inch

  • 10 threads per inch

Thread form according to Metric Screw Threads ISO 724

  • 2.5 mm pitch

  • 3 mm pitch

  • 3.5 mm pitch

  • 4 mm pitch

  • 4.5 mm pitch

  • 5.5 mm pitch

  • 6 mm pitch

  • 8 mm pitch

All models are made of SS304 and available in 1% and 0.1% scale divisions.