External Supermicrometer B - Model B250, B375, B500, B625

The Standard of Accuracy

If you're looking for a direct-reading vernier-style bench micrometer and an electronic size comparator for use in the calibration laboratory or on the production floor, look no further, the second-generation External Supermicrometer Model B provides durability, speed of measurement, and range of applications.  The Supermicrometer is the most popular bench micrometer in the world that can measure just about any manufactured precision OD part, turned part, or gages such as pins, plugs, and threads including API, NPT, NPTF, BSPP, BSPT, UN (Unified), M Profile (Metric), ACME, Buttress, UTS, UNC, UNF, UNEF, UNS, BSW (Whitworth), BA, BSC, BSF, BSP, to name a few.

The External Supermicrometer® Model B measures:

  • Your Precision Parts
  • Pin & Plug Gages
  • External Thread Gages
  • Dial / Test Indicators
  • Taper Threads - Pipe Threads (API Gages)
  • Dial Bore Gages
  • Cylindrical Setting Gages
  • Spheres
  • Setting Masters / Setting Gauges
  • Taps, Dies, and Cutting Tools
  • Gears / Splines
  • Feeler Gages 

Features & Benefits of the External Supermicrometer® Model B:

  • Heavy-duty cylindrical bed - Chromium-plated cylinder ensures long life and performance integrity and the rack and pinion drive eliminates movement during the measuring cycle
  • Adjustable pressure tailstock - Exclusive Electrolimit® tailstock offers adjustable pressure from 2 to 48 ounces (50 to 1350 g) for reliability and optimum performance of your Supermike.  Adjustable pressure is required for thread gage calibration and using 3-wires for Pitch Diameter (PD) measurement.
  • Carbide-tipped measuring spindles - Non-rotating measuring spindles have long life, corrosion-free lapped anvils and are calibrated to ultra finish and precision.  A must for measuring thousands of pins or precision components.
  • Elevating table - Adjustability allows for presentation of the part to the instrument in a non-influencing manner.
  • Calibrated analog meter - Along with reading the vernier scale, establishes the reference zero for taking measurements in 0.000020 inch (0.50 micron) or 0.000010 inch (0.25 micron) increments for high resolution.


Model / Part #
U302526 (U50055)**
Units English Metric English Metric English Metric English Metric
Accuracy 50 µinch 1.25 µm 50 µinch 1.25 µm 50 µinch 1.25 µm 50 µinch 1.25 µm
Repeatability 20 µinch 0.5 µm 20 µinch 0.5 µm 20 µinch 0.5 µm 20 µinch 0.5 µm
Measurement Range 0-10 inches 0-250 mm 0-15 inches 0-375 mm 0-20 inches 0-500 mm 0-25 inches 0-625 mm
Direct Reading Range 1 inch 25 mm 1 inch 25 mm 1 inch 25 mm 1 inch 25 mm
Measuring Force 2-48 oz. 50-1350 g 2-48 oz. 50-1350 g 2-48 oz. 50-1350 g 2-48 oz. 50-1350 g

*Model B-1000 also available: 0-40 inch (1000mm) measurement range 

**Previous part number U50055. [NSN 5210-00-078-1377]  

NEW Accessory / Upgrade - Digital Tailstock Meter:

  • Compatible with Supermicrometer Model B, C, or PC
  • 1 millionth of an inch resolution [0.000001 inch (0.025 micron)]

Retrofit - Model B, Model C, Model PC: