Precision Twist Drill 5998979 Letter X Hss Jobber Drill Bit

Product Description

The PRECISION TWIST DRILL 5998979 is a jobber-length drill bit sized at Letter X (0.3970 inches) designed for general-purpose drilling in a wide range of materials. Built from high speed steel with a steam oxide coating, this bit runs a 135-degree split-point angle that reduces walking on entry and lowers thrust requirements compared to standard 118-degree points. The straight-cylindrical shank measures 0.3970 inches in diameter and fits standard drill chucks without adapters. With an overall length of 5.125 inches and a flute length of 3.75 inches, this bit handles drilling depths up to 3.75 inches. It is sold individually and suited for use in machine shop, maintenance, and fabrication environments.

This drill bit is intended for use on steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium. It fits production drilling applications where a heavy-duty, general-purpose bit is required. The regular spiral flute geometry and 9xD flute-to-diameter ratio support efficient chip evacuation across these workpiece categories. The web-thinned, tapered web configuration reduces cutting resistance, making it practical for both handheld drill presses and CNC setups where Letter X sizing is specified.

Key Features

• Letter X size at 0.3970 inches decimal equivalent for precise hole sizing
• 135-degree point angle with web thinning reduces walking and entry thrust
• High speed steel construction with steam oxide coating for heat and wear resistance
• Right-hand spiral flute with regular helix for efficient chip removal
• Straight-cylindrical shank fits standard drill chucks without adapters
• Meets ANSI and NAS 907 standards; Series R10B-R15B-R18B

Compatibility

Designed as a general-purpose jobber-length drill bit compatible with any standard drill chuck accepting a 0.3970-inch straight-cylindrical shank, including bench drill presses, radial arm drills, and CNC machining centers.

Installation Notes

This bit is installed by a machinist or qualified tradesperson using a standard keyed or keyless drill chuck. Secure the shank fully in the chuck and verify concentricity before drilling. Use appropriate cutting fluid or coolant for the workpiece material, particularly when drilling stainless steel or superalloys, to extend tool life. Power down and de-energize any machine tool before changing bits or adjusting chuck position.