Spi 21-988-1 Test Indicator Ball Contact Point

Product Description

The SPI 21-988-1 is a ball-style contact point designed for use with dial test indicators requiring precise, repeatable surface contact. The hardened stainless steel ball tip measures 0.039 inches in diameter and the overall contact point length is 0.54 inches, making it suited for measuring in tight bores, grooves, and recessed features where a standard stylus cannot reach. This replacement contact point threads into compatible test indicator stems and is installed by metrology technicians, machinists, and quality control personnel working with precision measurement equipment in shop or laboratory environments.

This contact point is intended for applications where a small-radius ball tip is needed to probe fine features, undercuts, or contoured surfaces on machined parts. The stainless steel construction resists corrosion and wear during repeated contact cycles. It is a direct accessory for the SPI Integral Series test indicator line, providing an OEM-style replacement or supplemental tip for technicians expanding their measurement capability.

Key Features

• 0.039 inch ball diameter for probing fine features and small-radius geometry
• 0.54 inch contact point length suitable for recessed and hard-to-reach measurement surfaces
• Stainless steel construction for corrosion resistance and long service life
• Tip diameter of 0.039 inches matches ball diameter for consistent contact geometry
• Lightweight at 0.01 pounds — minimal added mass on indicator stem

Compatibility

Designed for use with the SPI Integral Series test indicators. Verify thread size and stem compatibility before installation.

Installation Notes

Contact point replacement on dial test indicators is performed by metrology or machine shop personnel. Before replacing the contact point, remove the indicator from any active measurement setup and secure the indicator body to prevent rotation damage to the spindle. Use the appropriate small wrench or contact point tool to thread the tip in by hand first, then snug gently — do not overtighten, as the threaded stem on test indicators is fine-pitch and easily damaged. Inspect the replacement tip for burrs or surface defects before returning the instrument to service.