Spi 21-129-2 Ruby Ball Contact Point Tesa Test Indicators

Product Description

The SPI 21-129-2 is a ruby ball contact point designed for use with dial-type test indicators. The contact point features a 2.00 mm (0.078 inch) ruby ball tip and a contact point length of 0.497 inches. Ruby is the preferred tip material in precision measurement applications because its hardness resists wear and its smooth surface minimizes friction against the workpiece. This contact point is installed by metrology technicians and machinists who require consistent, repeatable surface contact during inspection and measurement routines.

This contact point is intended for use with Tesa test indicators in inspection and quality control applications. Typical use cases include surface runout checks, bore alignment, part concentricity verification, and setup work on mills, lathes, and surface plates. The compact tip geometry is suited for accessing tight features and small bores where a larger contact point would not seat properly.

Key Features

• Ruby ball tip for wear resistance and low-friction surface contact
• Ball diameter of 0.078 inches (2.00 mm) for access to tight features
• Contact point length of 0.497 inches
• Designed for compatibility with Tesa test indicators
• Lightweight construction at 0.1 pounds for minimal indicator load

Compatibility

Designed for use with Tesa test indicators as specified by the manufacturer.

Installation Notes

Installation is performed by threading or pressing the contact point into the indicator stylus stem according to the indicator manufacturer's torque and fitment guidance. Handle ruby tips carefully during installation and removal, as the ball is brittle and will chip under impact or side-loading. Always zero the indicator after swapping contact points to account for any length variation. No special tools or trade licensing are required for contact point replacement.