Precision Twist Drill 5998158 Cobalt Jobber Drill 11/16 in

Product Description

The PRECISION TWIST DRILL 5998158 is a heavy-duty cobalt jobber-length drill bit designed for drilling into steel and other demanding workpiece materials. Built to NAS 907 and ANSI standards, it features a 135-degree split point that reduces walking and lowers the thrust required to start a hole. The straw oxide finish provides surface hardness and mild lubricity. With an overall length of 7.625 inches and a 2-flute regular spiral flute design, this bit delivers efficient chip evacuation in general-purpose production and maintenance drilling applications.

This drill bit is suited for drilling ferrous metals, cast iron, nonferrous alloys, and superalloys, covering primary workpiece material codes P, M, K, N, and S. It is used in metalworking shops, industrial maintenance environments, and mechanical contractor settings where high-speed steel bits lack the heat and wear resistance required. The web-thinned, tapered-web construction reduces cutting resistance at the chisel edge, making it a practical choice for repetitive or deep-hole drilling cycles in harder steel stock.

Key Features

• Cobalt construction for superior heat resistance and wear life in steel and hard alloys
• 135-degree split point reduces bit walking and lowers entry thrust
• Straw oxide finish adds surface hardness and mild corrosion resistance
• Web-thinned tapered web reduces cutting force at the chisel edge
• Regular spiral flute geometry promotes efficient chip evacuation
• Meets NAS 907 and ANSI standards for dimensional consistency

Compatibility

Part of the R10CO-R15CO-R18CO series. Designed as a general-purpose cobalt jobber drill bit for use in standard straight-shank drill chucks across benchtop drill presses, floor-standing machines, and hand-held drilling equipment accepting 11/16 inch straight-cylindrical shanks.

Installation Notes

Installation is typically performed by machinists, tool-and-die technicians, or mechanical contractors. Secure the straight shank firmly in a properly sized drill chuck before operation and verify chuck key is removed before powering the machine. Do not exceed the rated drilling depth of 5.625 inches and avoid forcing the bit through material at feed rates that cause excessive heat buildup. Coolant through is not supported on this bit, so external cutting fluid is recommended when drilling deep holes in hard steel.