StressTel BoltMike III

The BoltMike III ultrasonically measures tension and clamp load of threaded fasteners. A large, bright, easy-to-read display; rapid calibration and setup; and automatic temperature compensation ensure fast, repeatable, and accurate fastener tension measurements in many diverse applications:

Aerospace - Control tightening of bolted engine joints and aircraft wheel assemblies.

Automotive - Confirm tension of installed engine headbolts, connecting rod bolts, and main bearing bolts PLUS monitor torque and tensioning tools.

Injection Molding Machines - Measure elongation on tiebars and tierods.

Power Generation - Verify tension on manway studs and confirm uniform loading of gasketed flange bolts.

Oil/Petrochemical - Measure tension in leg fasteners of offshore platforms, confirm uniform loading of gasketed flange bolts in pipelines, and verify tension of vessel, reactor, and heat exchanger bolts.

Key BoltMike III Features

  • Simultaneous display of fastener load, stress, and elongation.
  • Long 40 hour life with five standard “AA” alkaline batteries.
  • High resolution 1/4 VGA LCD display to verify signal and optimize probe placement.
  • LARGE DIGIT and bargraph display with limits for fast testing.
  • Automatic temperature compensation.
  • Built–in probe zero block allows easy exchange of transducers.
  • Regression analysis for custom material calibration.
  • WINDOWS™ software to download measurements, create reports, and upload test parameters.
  • Direct to printer reports.

Ultrasonic Measurement of Fastener Load

An ultrasonic pulse, generated in the transducer, is transmitted into the fastener. The pulse travels down the length of the fastener and is reflected back from the end. The BoltMike III measures the total pulse transit time.

Fastener Length=(total pulse transit time / 2) X (material constants)

Fastener Elongation=(fastener length AFTER tensioning)–(fastener length BEFORE tensioning)

Fastener Load=(fastener elongation) X (geometric and material constants)

Physical Description

Width: 7.5 in (191 mm)

Height: 5.5 in (140 mm)

Depth: 2.2 in (56 mm)

Weight: 2.5 lbs (1.14 kg) with batteries

Shock resistant plastic case

Weather resistant key pad


Graphic Waveform LCD: 1/4 VGA

Viewing Area (w x h): 3.8 x 2.8 in/ 96 x 71 mm

Pixel Density (w x h): 320 x 240

Update Rate: 4 Hz

Adjustable contrast and backlight

Four level ZOOM for signal enlargement

Test Specifications

Measurable Fastener Length: 0.75 to 250 in/19 to 6350 mm

Fastener and Test Memory: 10,000 fasteners in 512 groups

Measurement Modes: Initial to first pulse; multiple echo for short fasteners

Units: Load, stress, and elongation in English and Metric units

Stored material constants: 12 common fastener materials


5 “AA” Alkaline or NiCad batteries

Interchangeable and easy–to–access

Operating time: 40 hours w/o backlight

A.C. Power (85 to 260 volt)


STRESSWARE (WINDOWS™ 95/98/ME/NT/2000) to download measurements, create reports, and upload test parameters.


+10 to +120 F/-10 to + 50 C