Bridgeport 12550004 Varidisc Drive Key Assembly

Product Description

The BRIDGEPORT 12550004 is a Varidisc Drive Key Assembly designed for use in Bridgeport milling machines equipped with the 2J-Head Top Housing. This component is part of the variable-speed drive system that controls spindle speed by transmitting rotational force between the varidisc drive assembly components. When this key wears or shears, the spindle speed becomes erratic or unresponsive. Replacing it restores proper drive engagement and accurate speed control. Installation is typically performed by a machinist or millwright during a scheduled maintenance interval or following a drive failure diagnosis. The part ships as a single-piece assembly.

This key assembly fits the 2J-Head Top Housing configuration found on I Series Bridgeport milling machines. It is used in both job shop and production environments where Bridgeport knee mills are in active service. Technicians servicing variable-speed head assemblies will encounter this part during top housing disassembly when inspecting or replacing varidisc drive components. No compatibility beyond the stated machine type is confirmed by the input data.

Key Features

• OEM-style replacement for the Varidisc Drive Key Assembly in Bridgeport 2J-Head configurations
• Restores proper rotational drive engagement in variable-speed spindle systems
• Fits I Series Bridgeport milling machines with 2J-Head Top Housing
• Compact single-piece component weighing 0.25 pounds for straightforward field replacement
• Sold individually — minimum order quantity of one unit

Compatibility

Designed for use with I Series Bridgeport milling machines equipped with the 2J-Head Top Housing varidisc drive system.

Installation Notes

Installation is performed by a qualified machinist or millwright. Before servicing the top housing, power down the machine and lock out the main disconnect per OSHA lockout/tagout procedures. Disassemble the 2J-Head Top Housing per the manufacturer service documentation before removing or installing the drive key. Inspect surrounding varidisc components for wear before reassembly to avoid repeat failure.