01M604 - 1-1/16 Inch HSS Cobalt Reduced Shank Drill Bit

Technical Overview of the Walter SST+ Prentice Drill Bit

The Walter 01M604 is a high-performance 1-1/16 inch Prentice drill bit belonging to the renowned SST+ series. Engineered for industrial maintenance and heavy-duty fabrication, this tool bridges the gap between large-diameter hole requirements and standard portable tooling limitations. The defining characteristic of the Prentice style is its reduced shank; while the cutting diameter is a substantial 1-1/16 inches, the shank is machined down to 1/2 inch. This allows operators to utilize standard hand drills, magnetic drills, and drill presses with 1/2-inch chuck capacities to bore large holes without requiring Morse taper fixtures or heavy stationary machinery.

Metallurgically, the 01M604 is constructed from a premium cobalt blend High Speed Steel (HSS). The addition of cobalt significantly increases the red hardness of the bit, allowing it to maintain a sharp cutting edge at the elevated temperatures generated when drilling tough alloys like stainless steel. The surface is finished with Walter's exclusive bronze SST treatment, which serves a dual purpose: it reduces the coefficient of friction between the tool and the workpiece to minimize heat buildup, and it facilitates smoother chip evacuation through the flutes.

Geometric precision is central to the performance of this bit. It features a 135-degree split point, a self-centering design that engages the material immediately upon contact. This eliminates the common issue of "walking" or wandering, particularly on round surfaces such as pipes or tubing, and negates the need for pre-drilling pilot holes. Furthermore, the shank is engineered with three precision-ground flats. These flats positively engage with the jaws of the drill chuck, ensuring maximum torque transmission and completely preventing the bit from spinning inside the chuck during heavy load operations.

This drill bit is optimized for use on a wide range of materials, including mild steel, high-tensile steel, stainless steel, and non-ferrous metals. Its robust web construction provides the rigidity necessary to withstand the radial forces encountered in portable drilling applications, making it an indispensable tool for MRO professionals.