Starrett 78MXTZ-20 Inside Bore Gage Micrometer, 16-20mm, 0.005mm, 0.004mm

Original price was: $967.00.Current price is: $854.00.

The Starrett 78MXTZ-20 3-point contact gage has a measurement range of 16mm to 20mm with a measuring depth of 62mm. It can measure the inside diameter of cylindrical holes in steel and other materials.

Add 5-7 days for calibration

Product Description

The 78MXTZ-20 Bore Gage features extended travel, reducing the need to exchange anvils. The ground contact points seat the internal micrometer faster and more accurately than the spherical contacts found in other gages. The rugged and accurate 78MXTZ series internal micrometers are available individually or in economical sets from .080-12″ (2-300mm).

Designed to measure internal cylindrical holes and grooves, this gage can measure in metal, plastics, and other materials. The 78MXTZ-20 features a 3-point contact with a hardened point to ensure accurate measurements. The 16-20mm range allows for the measurement of holes between 16 and 20 millimeters in diameter. The 62mm measuring depth allows this model to measure holes up to 2 inches deep.


  • Wide measurement range without changing anvils
  • Resolution from .0001″ (0.0025mm) on the 2-point contact tools up to 3/4″ (20mm) and .00025″ (0.005mm) on the 3-point contact tools ranging from 3/4″-12″ (20mm – 300mm) 
  • Tungsten carbide measuring faces on all 3-point heads above 1/2″ (12.5mm)
  • Ratchet stop ensures consistent measurements
  • Self-centering contacts for true readings
  • Blind bore measuring capability above 1/2″ (12.5mm) diameter
  • Extensions available up to 6″ (150mm) for deep hole measuring
  • Setting rings included
  • Depth stop/collar also available for .080″-.250″ (1-6mm) range
  • Each micrometer bore gage comes in a case, complete with a setting ring, contacts, wrenches, and instructions


  • Manufacturing
  • Machining
  • Automotive
  • Aerospace
  • Energy
  • Defense


  • Check bore holes prior to assembly or maintenance
  • Check the accuracy of machining operations after completion
  • Measure the inside diameter of a hole
  • Test the quality of pistons, rods, and sleeves
  • Ensure products meet certain size requirements

About Starrett

The L.S. Starrett Company is a world leader in precision measuring tools and instruments. Since 1880, they have been an industry standard. Starrett’s high quality and durability have made the brand an industry standard for decades. They produce products for various industries, including aerospace, automotive, manufacturing, and commercial construction. Today, they’ve expanded into metalworking, making saw blade products for manufacturing operations worldwide.

Additional Information

Weight 1.8 lbs
Dimensions 7.6 × 5.6 × 2.5 in




Movement of Screw


Operation Type


Thimble Type





Contacts; Setting Ring; Wrenches

Lock Nut Type



±0.004 mm

Max. Measuring Depth


Contact Point Material


Inside Micrometer Type

3-Point Inside Micrometer

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