Spi 20-645-8 Contact Point Extension 3 Inches 4-48

Product Description

The SPI 20-645-8 is a drop indicator contact point extension designed to increase the reach of a dial indicator contact point by 3 inches. Machined from steel, this extension threads directly onto the contact point stem using a 4-48 thread, a standard thread size found on most dial indicator and test indicator assemblies. It is used by machinists, metrology technicians, and quality control professionals who need to access recessed bores, deep features, or hard-to-reach measurement surfaces without changing the base indicator setup. The 0.15-pound weight keeps added mass low to avoid influencing indicator sensitivity.

This contact point extension is suited for use in machine shops, manufacturing facilities, and inspection departments where standard contact point length is insufficient for the application. It is compatible with any dial indicator or test indicator that accepts a 4-48 threaded contact point, making it a versatile addition to a metrology toolkit. Typical applications include bore gauging, slot measurement, and surface runout checks on deep or recessed workpieces.

Key Features

• 3-inch extension length provides added reach for deep or recessed measurement surfaces
• 4-48 thread is the industry-standard contact point thread for dial and test indicators
• Steel construction for rigidity and dimensional stability during measurement
• Low mass at 0.15 pounds minimizes influence on indicator sensitivity
• Single-piece unit ships individually, no assembly required

Compatibility

Compatible with any test indicator or dial indicator that accepts a standard 4-48 threaded contact point.

Installation Notes

Installation requires no special tools beyond fingers or a small wrench to snug the 4-48 thread connection — avoid overtightening, which can strip the fine thread. Zero the indicator after attaching the extension to account for any angular deflection introduced by the added length. Extended contact points can amplify cosine error; ensure the extension is aligned as closely as possible to the measurement axis before taking readings.