Spi 20-640-9 Drop Indicator Contact Point Extension

Product Description

The SPI 20-640-9 is a contact point extension designed for use with drop-style dial test indicators. It threads directly into the indicator spindle using a 4-48 thread and adds 1.25 inches of reach to the existing contact point. This extension is machined from steel for durability and dimensional stability under repeated use. Metrology technicians, machinists, and quality control inspectors install this type of accessory when standard contact point reach is insufficient for the measurement setup. It is a straightforward, single-piece component with no moving parts.

This extension is suited for shop floor and inspection room environments where a dial test indicator must reach into a bore, recess, or tight geometry that the standard contact point cannot access. Its 4-48 threaded connection is a common standard in indicator accessories, making it compatible with a wide range of drop-style dial test indicators. It is typically used on manual surface plates, CMM setups, or machine tool inspection routines where extended reach is required without sacrificing indicator sensitivity.

Key Features

• Adds 1.25 inches of contact point reach to drop-style dial test indicators
• 4-48 threaded connection matches common dial indicator spindle standards
• Steel construction provides rigidity and wear resistance
• Single-piece design with no moving parts or adjustment required
• Lightweight at 0.15 pounds — minimal added mass to the indicator stylus

Compatibility

Designed as a contact point extension for any dial test indicator equipped with a 4-48 threaded spindle tip. Verify thread size on the indicator before installation.

Installation Notes

Installation requires no special tools beyond a steady hand and care not to cross-thread the 4-48 connection. Snug the extension by hand or with light finger pressure — overtightening a fine thread can damage the indicator spindle. Zero the indicator after attaching the extension to account for any runout introduced by the added length. This work is typically performed by machinists or metrology technicians in accordance with shop calibration procedures.