Bolt strain gauge installation / calibration service

Bolt strain gauge installation / calibration service

Currently, bolts are used in various fields for connecting structural members. Confirmation and management of the fixing condition are possible by measuring axial force applied to the bolt in machine structures, cars, airplanes, expressways, bridges, fixing of segments, and so on. Also the axial force measurement is useful for knowing the strength of bolt and designing the bolt connection.
TML offers strain gauging service for measurement of axial force acting on bolts. The service includes drilling a hole, fixing the gauge, connecting the cable, and applying load calibration to the bolt supplied by the customer. Strain gauge installation service for high temperature is also available.

Bolt strain gauge installation / calibration service

Strain gauge installation service



Construction with any of embedded bolt gauges or surface-adhering gauges. We can also handle special-shaped bolts upon consultation. Usable in a wide range of temperatures from low to high temperatures.

Processing method

There are two methods in strain gauge installation service. One is embedding, and the other is bonding. Choose between them according to the conditions of use.

Embedding: BTM series

A hole of 1.6mm or 2mm in diameter is drilled in the center of the bolt. The strain gauge is inserted into the hole and embedded with an exclusive adhesive. This method has the advantage of avoiding the gauge being damage by a washer, etc. while fastening the bolt.


Bonding: F, QF, ZF, CF series

Two strain gauges are bonded on both sides of the bolt shaft in axially symmetric positions to cancel the influence of bending. It is required to slightly scrape off the surface of the bolt shaft where the strain gauges are bonded, for the purpose of avoiding strain gauges being damaged while fastening the bolt or by contact of a washer. Choose strain gauges according to the usage conditions including temperature.

Calibration service


In order to achieve accurate measurement, we offer calibration service in which the bolt is calibrated with specified load. Instruments and calibration machines used for the calibration service are periodically calibrated and inspected by public institutions complying with the national standards.

Application example


Monitoring of axial force of bolts in joint parts

Wind turbine generator facilities are aimed at enlargement in the scale. Management of axial force is indispensable for the bolts used in joint parts of the structures, both in assembling process and in actual working condition. It is possible to continuously monitor the axial force by installing bolt strain gauges in some of the bolts used in the joint part.