Spi 21-255-5 Flat Button Contact Point Dial Indicator

Product Description

The SPI 21-255-5 is a flat button contact point designed for use with dial indicators in precision measurement applications. Machined from black oxide steel, this contact point threads into standard dial indicator stems using a 4-48 thread and provides a 0.094-inch contact length with a 0.5-inch diameter flat button face. The black oxide finish resists corrosion and reduces light reflection during inspection work. Machinists, toolroom technicians, and quality control professionals install this contact point when a broad, flat sensing surface is required for accurate surface readings on flat or slightly curved workpieces.

This contact point is suited for dimensional inspection setups on surface plates, fixture gages, and machine tool work-holding verification. The AGD Group 1 industry designation confirms compatibility with standard dial indicator spindle threads common in precision measurement tooling. It is appropriate for use in both shop-floor and inspection-room environments where repeatability and consistent contact geometry matter.

Key Features

• Flat button contact face provides broad surface contact for stable, repeatable readings
• Black oxide steel construction resists corrosion and minimizes glare
• 4-48 thread size fits standard dial indicator spindle stems
• 0.094-inch contact point length suits close-clearance measurement setups
• 0.5-inch diameter button face distributes contact load across a wider area
• AGD Group 1 industry designation ensures fit with compatible indicators

Compatibility

Designed for use with dial indicators accepting a 4-48 threaded contact point, conforming to AGD Group 1 standards. Specific indicator model compatibility should be verified against the indicator manufacturer thread specification before installation.

Installation Notes

Installation is performed by hand-threading the contact point into the dial indicator spindle stem. No power shutoff is required, but the indicator should be removed from any active gage fixture before changing contact points to avoid accidental spindle damage. Do not overtighten — contact points are typically seated finger-tight or with light tool assistance only. Verify zero and re-calibrate the indicator after any contact point change.