Spi 20-638-3 Drop Indicator Contact Point Extension

Product Description

The SPI 20-638-3 is a 3/4 inch drop indicator contact point extension designed to increase the reach of a dial indicator contact point during precision measurement work. Machined from steel, this extension uses a 4-48 thread to mount securely onto compatible dial and test indicators. It is a standard accessory in metrology and quality control environments where additional stylus depth or offset clearance is required to reach a recessed surface, bore, or hard-to-access feature. Machinists, tool and die makers, and quality technicians install this type of extension when the standard contact point cannot reach the target measurement surface directly.

This extension is suited for use in machine shops, production floors, and inspection labs. It applies to any setup where a dial or test indicator requires extended contact reach, such as measuring inside bores, recessed slots, or stepped surfaces. The 4-48 threaded connection is a common standard thread pitch used across a wide range of dial and test indicator contact points, making this a frequently stocked consumable for inspection tooling kits.

Key Features

• 3/4 inch extension length adds reach to standard contact points
• 4-48 thread size matches common dial and test indicator contact point threads
• Steel construction provides durability and dimensional stability
• Compact, lightweight design at 0.1 pounds
• Compatible with a broad range of dial and test indicators per manufacturer application note

Compatibility

Designed for use with any test indicator or dial indicator that accepts a standard 4-48 threaded contact point extension.

Installation Notes

Installation requires no special tools — thread the extension onto the indicator contact point stem by hand and snug it carefully to avoid cross-threading the 4-48 thread. Ensure the indicator is removed from active measurement or the spindle is retracted before swapping contact point accessories. Verify the extension is fully seated and free of lateral play before taking measurements, as any looseness will introduce error into readings. This accessory is typically handled by machinists or quality technicians familiar with dial indicator setup and calibration procedures.