Spi 21-280-3 Radius Contact Point Dial Indicator

Product Description

The SPI 21-280-3 is a radius-style contact point designed for use with dial indicators in precision measurement applications. Machined from steel, this contact point threads directly onto AGD Group 1 dial indicators using a 4-48 thread. The spherical radius tip provides consistent, repeatable point contact on curved, flat, or irregular surfaces. At 0.5 inches in contact point length and 3/16 inches in diameter, it is sized for general-purpose indicator work on machine tools, surface plates, and inspection fixtures. Metrology technicians, machinists, and quality control professionals install this type of contact point as part of routine setup and calibration workflows.

This contact point is suited for dimensional inspection tasks in both shop-floor and laboratory environments. It is compatible with AGD Group 1 dial indicators, making it a standard replacement or supplemental tip for indicators used in surface runout checks, bore measurement setups, and part alignment procedures. Its steel construction holds up to repeated contact cycles in production measurement environments where durability and tip geometry consistency are required.

Key Features

• Radius contact point style for consistent point contact on varied surface geometries
• Steel construction for durability in production and inspection environments
• 4-48 thread for direct installation on AGD Group 1 dial indicators
• 0.5 inch contact point length for standard indicator reach
• 3/16 inch diameter provides a compact tip profile

Compatibility

Designed for use with AGD Group 1 dial indicators that accept a 4-48 threaded contact point.

Installation Notes

Contact point replacement requires no special tooling beyond a contact point wrench or appropriate flat-jaw tool to avoid damaging the indicator stem. Ensure the indicator spindle is in the retracted position before removing or installing a contact point. Thread the 21-280-3 in by hand first to avoid cross-threading the 4-48 connection, then snug firmly without over-torquing the delicate indicator threads.