48M639 - Walter 48M639 Replacement Motor Cap for Big-Buff III and Line-Mate III

Genuine Walter 48M639 Motor Cap Replacement

The Walter 48M639 Motor Cap (2 Parts) is a critical OEM replacement component designed specifically for Walter Surface Technologies' premium finishing tools, including the Big-Buff III and the Line-Mate III. When operating industrial power tools in heavy-duty environments, the exterior housing is the first line of defense against impact, drops, and the harsh ingress of conductive metal dust. This replacement cap assembly restores the integrity of your tool's rear housing, ensuring that the motor remains protected and the operator remains safe from electrical hazards.

This assembly consists of two parts, typically the main rear housing shell and the access cover, which fit together seamlessly to enclose the motor's commutator and carbon brushes. Using genuine Walter parts is essential for maintaining the tool's IP rating and cooling efficiency. The motor cap is engineered with specific ventilation slots that direct airflow over the motor windings; a cracked or non-OEM cap can disrupt this airflow, leading to overheating and premature motor failure. Additionally, the high-impact composite material used in the 48M639 is designed to withstand the heat generated during prolonged use without warping.

Technical Importance of Housing Integrity

In metalworking environments, airborne particulates are often conductive. If the motor cap is cracked or missing, these particles can be sucked directly into the brush assembly, causing arcing, short circuits, and permanent damage to the armature. Replacing a damaged cap immediately with the 48M639 prevents these costly internal failures. Furthermore, the cap provides the necessary ergonomic grip surface at the rear of the tool, allowing for precise control during delicate finishing operations.

Installation and Maintenance

Installing the 48M639 is a straightforward repair that can be performed on the bench. It utilizes the existing screws from your tool (hardware not included). When replacing the cap, it is also an excellent opportunity to inspect the condition of your carbon brushes and blow out any accumulated dust from the motor housing with compressed air. Keeping your Big-Buff III or Line-Mate III in top condition ensures consistent finishes and reduces downtime in your production line.

• OEM Fit: Guaranteed compatibility with specified Walter III-series tools.


• Safety: Shields operator from moving parts and electrical connections.


• Durability: Resistant to shop chemicals and physical impact.