Precision Twist Drill 5998639 Screw Machine Drill Bit

Product Description

The PRECISION TWIST DRILL 5998639 is a screw machine length drill bit designed for high-performance drilling in demanding trade and industrial applications. Built from high speed steel with a coated finish, this bit measures 0.159 inches (No. 21 wire gauge) in diameter with an overall length of 2-1/8 inches and a flute length of 1-1/16 inches. The 135-degree split point reduces walking and cutting force at entry, while the web-thinned, tapered web construction improves chip evacuation. It is suited for machinists, tool-and-die technicians, and maintenance professionals requiring precise, repeatable hole quality in tight-tolerance work.

This bit is engineered for right-hand spiral flute cutting with a straight-cylindrical shank, making it compatible with standard drill chucks and CNC tool holders. The screw machine length (stub) profile provides added rigidity over jobber-length bits, which is advantageous when drilling in confined spaces or when chuck clearance is limited. Its primary rated workpiece material is titanium, though the heavy-duty HSS construction also performs in ferrous and non-ferrous metals encountered in HVAC, plumbing, and general mechanical trades. The 2.5xD flute-to-diameter ratio supports efficient chip clearing at typical feed rates for this diameter range. Series R41C meets ANSI and NAS 907 specifications.

Key Features

• 0.159 inch (No. 21 wire gauge) diameter with 135-degree split point for reduced entry force and walk prevention
• High speed steel construction with coated finish for extended tool life in high-performance drilling
• Web-thinned, tapered web design promotes efficient chip evacuation
• Screw machine (stub) length adds rigidity over jobber-length bits in confined or short-reach applications
• Right-hand cut, regular spiral, straight-cylindrical shank fits standard drill chucks and CNC holders
• Meets ANSI and NAS 907 specifications for dimensional and performance consistency

Compatibility

Rated for use in titanium as the primary workpiece material; the straight-cylindrical shank fits standard 3-jaw drill chucks and compatible CNC tool holders. Designed for use within the 0.1500 to 0.2000 inch drill bit size range category of the Series R41C line.

Installation Notes

Installation and use should be performed by qualified machinists or maintenance technicians familiar with proper speeds and feeds for the workpiece material. Secure the shank fully in the drill chuck before operation and verify chuck key is removed prior to starting the spindle. Use appropriate cutting fluid or coolant for the workpiece material where applicable, noting this bit does not feature a coolant-through design. Inspect the cutting edges for wear or chipping before each use and replace if the split point geometry is compromised.