Precision Twist Drill 5999142 Letter W Jobber Drill Bit

Product Description

The PRECISION TWIST DRILL 5999142 is a jobber-length drill bit sized to Letter W, equivalent to 0.3860 inches in decimal, ground from high speed steel and finished with a steam oxide coating. The 135-degree split-point tip reduces walking and decreases thrust when starting a hole. Web thinning further eases penetration into harder stock. At 5.125 inches overall length with a 3.75-inch spiral flute and a straight-cylindrical shank, this bit fits standard drill chucks without an adapter. It is a general-purpose, heavy-duty tool suited for production drilling or maintenance work across a wide range of metallic materials.

This drill bit is rated for use in steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium. It is appropriate for any shop, job-site, or maintenance application where accurate letter-size holes are required in metal workpieces. The two-flute regular spiral design promotes chip clearance during through-hole drilling. Maximum drilling depth matches the flute length at 3.75 inches. The bit conforms to ANSI standards and carries a NAS 907 specification designation, making it a fit for aerospace and industrial work governed by those specs.

Key Features

• Letter W size — 0.3860 inch decimal equivalent for precise hole sizing
• 135-degree split-point tip reduces bit walking and lowers required thrust
• Steam oxide coating provides mild lubricity and corrosion resistance during storage
• Web-thinned, tapered-web construction for easier penetration in hard materials
• Straight-cylindrical shank fits standard 3-jaw drill chucks without modification
• Meets ANSI standards and NAS 907 specification for industrial and aerospace applications

Compatibility

Designed as an OEM-style replacement or standard jobber-length drill bit for use in any drill press, hand drill, or machining center equipped with a chuck that accepts a 0.3860-inch straight-cylindrical shank. Series R10B, R15B, and R18B.

Installation Notes

A licensed machinist or qualified trade professional should secure the bit firmly in a properly sized chuck before operation. Ensure the workpiece is clamped or fixtured to prevent rotation during drilling. Apply cutting fluid appropriate to the workpiece material to extend tool life, particularly when drilling stainless steel, superalloys, or titanium. Inspect the cutting edges for wear or chipping before each use and replace the bit if the point geometry is degraded.