Spi 12-408-1 Inside Dial Caliper Gage 3.25 to 4.25 in

Product Description

The SPI 12-408-1 is an inside dial caliper gage designed to measure internal diameters and bores in the range of 3.25 to 4.25 inches. It delivers readings at 0.001 inch graduation with an accuracy of 0.0015 inches, making it a reliable tool for close-tolerance inspection work. The gage features ball contact points that seat consistently against bore walls, reducing measurement error from improper contact. Built from a combination of aluminum alloy, copper alloy, and steel, the instrument balances durability with handling ease. It is used by machinists, quality control technicians, and maintenance tradespeople who require repeatable inside-diameter measurements without the setup time of a bore micrometer.

This inside dial caliper gage is suited for shop-floor inspection, incoming material verification, and in-process quality checks on machined bores, pipe fittings, and cylindrical housings. The 3.25 inch leg length positions the dial indicator centrally within the bore for stable, repeatable contact. It is appropriate for both production environments and light maintenance settings where a quick, direct-reading inside measurement tool is needed.

Key Features

• Measurement range from 3.25 to 4.25 inches covers common bore sizes in machined components
• 0.001 inch graduation for fine-resolution direct reading on the dial face
• 0.0015 inch accuracy supports close-tolerance inspection requirements
• Ball contact points provide consistent seating against cylindrical bore surfaces
• 3.25 inch leg length stabilizes the gage within the measurement range
• Multi-material construction: aluminum alloy, copper alloy, and steel components

Compatibility

Designed as a direct-reading inside measurement gage for use on machined bores, cylindrical housings, and fittings with internal diameters between 3.25 and 4.25 inches.

Installation Notes

This gage is a precision measuring instrument, not an installed component. Calibrate or zero the gage before use according to the manufacturer procedure. Keep contact points clean and free of chips or debris before taking measurements. Store the gage in its case when not in use to protect the dial mechanism and contact points from damage.