Precision Twist Drill 5996391 Taper Length Cobalt Drill Bit

Product Description

The PRECISION TWIST DRILL 5996391 is a taper length cobalt drill bit designed for high-performance drilling in demanding industrial and metalworking applications. Built to Series M51CO standards, it features a 9/64 inch (0.1406 inch decimal) diameter with a 135-degree split point for self-centering entry and reduced walking on hard or smooth surfaces. The spiral flute geometry runs 3 inches in length, with an overall length of 5-3/8 inches. A gold oxide coating indicates the cobalt-grade tool steel construction, which provides increased heat resistance and edge retention compared to standard HSS bits. This bit is installed by machinists, tool-and-die workers, and maintenance trades across production and repair environments.

This drill bit is suited for through-hole and blind-hole drilling in a wide range of materials including alloy steel, carbon steel, stainless steel, cast iron, malleable iron, hardened steel, aluminum, aluminum alloy, brass, bronze, high-strength bronze, copper, nickel, nickel alloy, magnesium, magnesium alloy, cermet, graphite, and reinforced plastic. Its taper length body provides additional reach compared to a jobber-length bit, making it useful in deeper drilling scenarios or where extended reach past a fixture is required. The straight cylindrical shank fits standard drill chucks without adapters.

Key Features

• Cobalt tool material with gold oxide finish for heat resistance and extended tool life in hard metals
• 135-degree split point reduces thrust force and provides self-centering entry without a center punch on most materials
• 3-inch spiral flute length with 6xD flute-to-diameter ratio for efficient chip evacuation
• Taper length body at 5-3/8 inches overall provides extended reach versus standard jobber bits
• Web-thinned tapered web construction reduces cutting resistance and heat buildup
• Right-hand cut, straight cylindrical shank fits standard drill chucks directly
• Meets ANSI standards; rated for heavy-duty grade performance

Compatibility

Designed as an OEM-style replacement or direct-fit taper length drill bit for use in standard drill chucks, drill presses, CNC machines, and hand-held power drills accepting a 9/64 inch straight cylindrical shank.

Installation Notes

This bit is installed by machinists, maintenance technicians, and metalworking professionals using drill presses, hand drills, or CNC equipment. Secure the straight shank firmly in a properly sized chuck before operation and confirm the workpiece is clamped or fixtured to prevent movement. Use appropriate cutting fluid or coolant when drilling ferrous metals and stainless steel to extend tool life and manage heat. Inspect the cutting edges for wear before each use and replace the bit if chipping or dulling is observed.