Spi 12-402-4 Inside Dial Caliper Gage 3/4 to 1-3/4 in

Product Description

The SPI 12-402-4 is an inside dial caliper gage designed to measure internal diameters and bores in the range of 0.75 inches to 1.75 inches. It reads directly on a dial face with a graduation of 0.001 inches and holds an accuracy of 0.0015 inches, making it suitable for close-tolerance inspection work in machining, maintenance, and fabrication environments. The gage features ball contact points for consistent seating against bore walls and has a leg length of 3.25 inches to reach into recessed or deep features. The body is constructed from a combination of aluminum alloy, copper alloy, and steel. Machinists, toolmakers, millwrights, and quality technicians are the primary users.

This inside dial caliper gage is used in production and maintenance settings where internal bore dimensions must be verified quickly and accurately without a dedicated bore gage setup. Typical applications include checking pipe fittings, machined housings, bearing bores, and hydraulic cylinder interiors that fall within the 0.75 to 1.75 inch measurement range. The ball contact point geometry accommodates slightly irregular or worn bore surfaces and helps reduce measurement error caused by rocking the gage. It is well suited for both shop-floor spot checks and more formal inspection routines.

Key Features

• Measurement range of 0.75 inches to 1.75 inches covers common small-bore applications
• 0.001 inch graduation allows direct reading without interpolation
• 0.0015 inch accuracy meets close-tolerance inspection requirements
• Ball contact points provide consistent contact in round and slightly irregular bores
• 3.25 inch leg length enables access to deeper bore features
• Multi-material construction: aluminum alloy, copper alloy, and steel components

Compatibility

Designed as a direct-use inside dial caliper gage for any application requiring internal measurement in the 0.75 to 1.75 inch range. Ball contact points are included and are the standard contact type for this gage.

Installation Notes

Zero the gage against a known reference ring gage or setting master before use. Insert the contact points squarely into the bore and rock the gage gently to find the true minimum reading, which represents the actual bore diameter. Keep the contact points clean and free of chips or debris to maintain measurement accuracy. Store the gage in its case when not in use to protect the dial mechanism and contact point tips.