Precision Twist Drill 5998203 Cobalt Jobber Drill 39/64 in

Product Description

The PRECISION TWIST DRILL 5998203 is a cobalt jobber-length drill bit designed for heavy-duty drilling in steel, stainless, cast iron, and other demanding workpiece materials. The bit measures 39/64 inch (0.6094 inch) in diameter with a 7-1/8 inch overall length and a 5-3/16 inch flute length, giving it the reach required for typical through-hole and deep-hole applications. The 135-degree split point reduces walking on entry and lowers thrust requirements compared to a standard 118-degree point. A straw oxide finish provides added lubricity and corrosion resistance. This bit is web-thinned for improved chip evacuation and reduced heat buildup during prolonged cuts.

The 5998203 is built for professional drilling operations in ferrous and nonferrous metals, including carbon steel, alloy steel, stainless steel, cast iron, and titanium alloys. It is well suited to production-floor environments, maintenance and repair operations, and fabrication shops where a reliable, general-purpose cobalt bit is required. The regular spiral flute geometry and straight cylindrical shank make it compatible with standard drill chucks and machine spindles found on drill presses, lathes, and CNC machining centers. It conforms to NAS 907 and ANSI standards, making it appropriate for aerospace and industrial procurement requirements.

Key Features

• Cobalt construction for extended tool life in hard and abrasive materials
• 135-degree web-thinned split point reduces thrust and prevents bit walking on entry
• Straw oxide finish improves lubricity and surface durability
• Regular spiral flute with tapered web geometry for efficient chip evacuation
• Straight cylindrical shank seats securely in standard drill chucks without adapters
• Meets NAS 907 and ANSI standards for dimensional and performance compliance

Compatibility

Part of the R10CO-R15CO-R18CO series. Designed for use in steel, stainless steel, cast iron, titanium alloys, and other materials coded P, M, K, N, and S per ISO workpiece material classification. Fits any standard drill chuck accepting a 39/64 inch straight shank.

Installation Notes

Installation and use of this bit should be performed by a qualified machinist or tooling professional. Secure the shank fully in the chuck before operating and verify spindle runout is within acceptable limits to avoid premature edge wear. Use appropriate cutting fluid or coolant for the workpiece material, particularly when drilling stainless or alloy steel. Follow shop safety protocols and applicable ANSI machining standards when operating drill presses or CNC equipment.