Precision Twist Drill 5999430 Jobber Drill Bit Letter U

Product Description

The PRECISION TWIST DRILL 5999430 is a jobber-length twist drill bit sized to Letter U (0.3680 inches decimal equivalent), designed for general-purpose drilling in metal and hard materials. Built from high speed steel with a steam oxide coating, it runs a standard 118-degree point angle and a two-flute spiral configuration with a web-thinned, tapered web for improved chip evacuation and reduced feed force. The straight-cylindrical shank seats directly in standard drill chucks without adapters. Overall length is 5 inches, with a flute length of 3.625 inches, making it a practical choice for through-hole and deep-feature work in production and field environments. Installed by machinists, maintenance techs, and tool-and-die professionals.

This drill bit is suited for right-hand drilling operations in a wide range of workpiece materials including steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium. It fits the 0.3500 to 0.4000 inch decimal inch size range and is appropriate for general-purpose metal removal tasks in both shop and field settings. The Series R10-R15-R18 designation covers jobber-length bits conforming to ANSI standards, making this a straightforward stock replacement for worn or broken Letter U bits in existing drill sets.

Key Features

• Letter U size — 0.3680 inches decimal equivalent — ANSI standard jobber length
• High speed steel construction with steam oxide coating for corrosion resistance and reduced friction
• 118-degree standard point angle for reliable entry on flat and curved metal surfaces
• Web-thinned tapered web reduces thrust requirements and improves chip flow
• Two-flute regular spiral configuration supports efficient chip evacuation
• Straight-cylindrical shank fits standard 3-jaw drill chucks without adapters

Compatibility

Designed as an ANSI-compliant jobber-length replacement drill bit for use in standard drill chucks accepting a 0.3680-inch straight-cylindrical shank. Rated for drilling steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium per workpiece material codes P, M, K, N, and S.

Installation Notes

Install and change drill bits only after the spindle has come to a complete stop and the machine is powered down or locked out per applicable OSHA lockout/tagout procedures. Seat the shank fully in the chuck and verify concentricity before operation. Coolant-through is not supported on this bit; apply cutting fluid externally when drilling stainless steel, superalloys, or titanium to manage heat buildup. Discard bits showing chipped edges, excessive wear, or runout rather than attempting regrind without proper grinding equipment.