Starrett 53086 Small Hole Gage 0.4 to 0.5 Inch Half Ball

Product Description

The STARRETT 53086 is a small hole gage designed for precise internal measurement of bores, holes, and slots in the 0.4 to 0.5 inch range. It features a half ball style head that expands to contact the bore wall, allowing the technician to transfer the measurement to an outside micrometer for an accurate reading. Overall length is 3.5 inches, making it easy to handle in tight spaces. Machinists, tool-and-die workers, and maintenance technicians use this gage when a standard telescoping gage or bore micrometer cannot access a small-diameter opening. At 0.016 pounds, it is a lightweight, single-piece instrument suited for bench or field use.

This gage is used wherever small internal diameters must be measured with precision. Common applications include checking cylinder bores, valve guides, bushings, bearing bores, and drilled holes in machine components. It is equally at home in a production shop, a maintenance facility, or a field service environment. The 0.4 to 0.5 inch range targets the smaller end of the small hole gage spectrum, complementing larger-range gages in a complete set. Plumbers and HVAC technicians may also use small hole gages when verifying port or orifice dimensions during equipment service.

Key Features

• Measurement range of 0.4 to 0.5 inches covers small bores and ports
• Half ball style head provides positive, repeatable contact with bore walls
• 3.5 inch overall length allows access to confined measurement points
• Lightweight at 0.016 pounds for fatigue-free single-hand use
• Used in combination with an outside micrometer for a direct, accurate reading

Compatibility

Designed as a standard small hole gage for general-purpose internal measurement in the 0.4 to 0.5 inch range. Compatible with any outside micrometer that covers the same range for final diameter reading.

Installation Notes

Small hole gages require no installation. Insert the half ball head into the bore, adjust the knurled knob until light drag is felt against the bore wall, then withdraw and measure across the ball with a calibrated outside micrometer. Always zero and verify your micrometer before taking a final reading. Handle the gage carefully to avoid damage to the ball head, which can affect measurement accuracy.