Starrett 72739 Outside Micrometer 12 in Ratchet Stop

Product Description

The STARRETT 72739 is a mechanical outside micrometer with a 12-inch maximum measurement range and a graduation of 0.0001 inches, delivering an accuracy of 0.0002 inches. It features a ratchet stop thimble for consistent measuring pressure and a satin chrome finish that reduces glare during use. The measuring faces use solid carbide inserts on both the anvil and spindle, extending service life in high-cycle shop environments. A ring-style lock nut secures the spindle position once a measurement is taken. This instrument is used by machinists, tool and die makers, quality control technicians, and precision fabricators who require reliable large-range outside diameter or thickness measurement.

The 72739 suits applications requiring accurate outside measurement of large workpieces up to 12 inches. Typical use cases include checking large-diameter shafts, structural stock thickness, and precision-machined components in manufacturing, tooling, and inspection departments. The flat anvil geometry accommodates a wide range of part profiles. Both the anvil and spindle diameters measure 0.3 inches (7.60 mm), providing a defined contact area. This micrometer is supplied with a lock nut and a wrench. Starrett number T436XRL-12 is the OEM reference for this instrument.

Key Features

• 12-inch maximum measurement range for large-workpiece inspection
• 0.0001-inch graduation with 0.0002-inch accuracy
• Ratchet stop thimble ensures repeatable measuring force
• Solid carbide measuring faces on both anvil and spindle for extended wear life
• Ring-style lock nut holds spindle position during reading or transfer
• Satin chrome finish reduces glare under shop lighting

Compatibility

Designed as a direct-use mechanical outside micrometer for large-range dimensional inspection tasks. Refer to Starrett number T436XRL-12 for OEM cross-reference.

Installation Notes

Outside micrometers require no installation, but should be calibrated against a certified standard or gauge block stack before use, particularly after transport or storage. Store in the supplied case or a clean, padded location away from temperature extremes to preserve accuracy. Clean the measuring faces with a lint-free cloth before and after each use. Never force the thimble against a workpiece — allow the ratchet stop to control contact pressure.