Precision Twist Drill 5998660 Drill Bit Letter E 1/4 in

Product Description

The PRECISION TWIST DRILL 5998660 is a jobber length drill bit sized to Letter E (0.2500 inches) with a 118-degree standard point angle. It is made from high speed steel with a steam oxide coating that reduces friction and extends tool life in production drilling environments. The bit features a two-flute regular spiral design with a straight-cylindrical shank, a 2.75-inch flute length, and a 4-inch overall length. This is a general purpose drill intended for use by machinists, maintenance technicians, and metalworking tradespeople who need a reliable, ANSI-compliant jobber bit for everyday metal drilling tasks.

The 5998660 is suited for drilling steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium in both production and maintenance-repair-operations contexts. Its 11xD flute-to-diameter ratio provides adequate chip clearance for moderate-depth drilling. The straight-cylindrical shank fits standard drill chucks found on benchtop drill presses, handheld drills, and CNC machines with appropriate toolholding. The Series R10 designation places this bit within PRECISION TWIST DRILL's general purpose jobber line, designed for common hole-making applications where coolant-through tooling is not required.

Key Features

• Letter E size: 0.2500-inch diameter with a diameter tolerance of -0.0007 to 0.0000 inches
• 118-degree standard point angle with web-thinned, tapered web configuration for easier starting
• High speed steel construction with steam oxide coating to reduce friction and inhibit corrosion
• 2-flute regular spiral design with a 2.75-inch maximum drilling depth
• Straight-cylindrical shank at 0.2500-inch diameter, 1.25 inches in length, with no flats
• ANSI-compliant general purpose grade suitable for a wide range of workpiece materials

Compatibility

Designed for drilling steel, stainless steel, cast iron, non-ferrous metals, superalloys, and titanium. Compatible with any standard drill chuck accepting a 0.2500-inch straight-cylindrical shank. Series designation covers R10, R15, and R18 product families within the PRECISION TWIST DRILL general purpose jobber line.

Installation Notes

This bit is installed and operated by machinists, maintenance technicians, and general metalworking tradespeople. Secure the shank fully in the drill chuck and verify there is no runout before beginning a cut. Coolant-through is not supported on this bit; apply cutting fluid externally when drilling hard or heat-sensitive materials. Inspect the cutting edges for wear before each use and replace the bit if chipping or excessive wear is present.