Precision Twist Drill 5999066 Cobalt Jobber Drill Bit Letter S

Product Description

The PRECISION TWIST DRILL 5999066 is a Letter S cobalt jobber-length drill bit designed for heavy-duty drilling in steel and other demanding workpiece materials. The bit measures 0.3480 inches in diameter with a 135-degree split-point geometry and web-thinned tip that reduces walking and lowers thrust force at entry. Overall length is 4.875 inches with a 3.5-inch flute length, giving it a 10xD flute-to-diameter ratio suited to through-hole and deep-hole applications. The straw oxide finish adds surface hardness and mild lubricity. This bit is aimed at machinists, tool-and-die workers, and maintenance mechanics working in production or job-shop environments.

This drill bit is built for general-purpose drilling in steel, stainless, cast iron, aluminum, and nonferrous alloys, covering primary workpiece material codes P, M, K, N, and S. The straight cylindrical shank fits standard drill chucks on bench drills, magnetic base drills, drill presses, and CNC machining centers. The regular spiral flute promotes chip evacuation in both through-hole and blind-hole configurations. It is well suited to fabrication shops, maintenance departments, and field service applications where a reliable general-purpose cobalt bit is required.

Key Features

• Letter S diameter (0.3480 inches) cobalt construction for strength in hard and abrasive materials
• 135-degree split point with web thinning reduces entry thrust and minimizes drill walk
• Straw oxide finish provides surface hardness and mild corrosion resistance
• 3.5-inch flute length supports a maximum drilling depth of 3.5 inches
• Right-hand cut, regular spiral flute for efficient chip clearing
• Straight cylindrical shank (0.3480 inches diameter, 1.375 inches long) fits standard chucks
• Meets ANSI and NAS 907 standards; graded heavy duty for demanding applications

Compatibility

Part of the R10CO-R15CO-R18CO series. Fits any drill chuck accepting a 0.3480-inch straight shank. Compatible with standard drill presses, hand drills, and CNC spindles configured for straight-shank tooling.

Installation Notes

Installation and use should be performed by machinists or qualified technicians familiar with rotating cutting tools. Secure the shank fully in the chuck and verify runout before drilling. Use appropriate cutting fluid or coolant when drilling steel to manage heat and extend tool life; note that this bit does not have coolant-through capability. Always wear eye protection and ensure the workpiece is firmly clamped before operation.