Spi 21-281-1 Radius Contact Point 4-48 Dial Indicator

Product Description

The SPI 21-281-1 is a radius-style contact point designed for use with dial indicators in precision measurement applications. Machined from steel, it features a 4-48 thread size and a 3/16 inch diameter with a contact point length of 1/4 inch (0.2500 inch decimal). This replacement contact point meets AGD Group 1 industry standards, making it a reliable choice for metrology professionals, quality control technicians, and machinists who require consistent, repeatable contact geometry when taking measurements on curved or contoured surfaces.

This contact point is suited for use in machine shops, inspection rooms, and manufacturing environments where dial indicators are used for setup, runout checks, bore alignment, and surface measurement. The radius tip geometry is particularly effective when measuring on cylindrical or spherical workpiece surfaces, providing a defined, repeatable contact area rather than a flat or point contact. It is compatible with AGD Group 1 dial indicators that accept 4-48 threaded contact points.

Key Features

• Radius contact point style for consistent contact on curved and contoured surfaces
• 4-48 thread size for standard AGD Group 1 dial indicator compatibility
• 3/16 inch tip diameter with 1/4 inch contact point length
• Steel construction for durability in workshop and inspection environments
• Meets AGD Group 1 industry designation

Compatibility

Designed for use with AGD Group 1 dial indicators that accept 4-48 threaded contact points, per AGD industry standards.

Installation Notes

Installation is performed by hand or with appropriate tooling to thread the contact point into the indicator spindle using the 4-48 thread. Avoid over-tightening, which can damage the spindle threads or alter indicator calibration. Power down or zero out the indicator before swapping contact points to prevent measurement errors. Verify calibration after replacement using a known reference standard.