Hertel 42201 21/64 Inch Cobalt Screw Machine Drill Bit

Product Description

The HERTEL 42201 is a screw machine length cobalt drill bit designed for demanding metal cutting applications. Built from M35 cobalt steel with an oxide straw finish, it delivers the heat resistance and hardness retention needed when drilling tough ferrous materials. At 21/64 inch (0.3281 inches) in diameter with a 135-degree split point, it starts on contact with minimal walking and reduces the thrust required to break through. The overall length is 2.9375 inches with a spiral flute length of 1.6875 inches. Licensed HVAC technicians, machinists, and industrial tradespeople reach for cobalt bits when carbon steel or standard high-speed steel falls short on hardened stock.

This bit is suited for production and maintenance drilling in hardened materials, heat-treatable alloyed steels, stainless steel, and titanium alloy. The screw machine length — shorter than a jobber bit — provides added rigidity and reduced deflection in drill press, turret lathe, and CNC mill applications where tool runout must be minimized. The 3xD flute-to-diameter ratio supports efficient chip evacuation in the short-bore geometries typical of screw machine work.

Key Features

• M35 cobalt steel construction for elevated heat resistance during high-speed drilling
• 135-degree split point for self-centering starts and reduced feed pressure
• Oxide straw finish provides mild lubricity and corrosion resistance
• Screw machine (stub) length adds rigidity and reduces deflection versus jobber-length bits
• Regular spiral flute with 3xD ratio supports consistent chip evacuation
• No coolant-through design — suited for external coolant or dry drilling setups

Compatibility

Designed as an OEM-style replacement or production-grade addition for any 21/64 inch drill chuck application; fits standard drill press, lathe turret, and CNC spindle setups accepting bits in the 0.3000 to 0.3500 inch decimal inch range.

Installation Notes

Installation is performed by machinists, tool-and-die tradespeople, or maintenance technicians. Secure the bit in a properly sized chuck and confirm runout before drilling. When working with stainless steel or titanium alloy, use appropriate cutting fluid to manage heat buildup and extend tool life. Inspect the cutting edges before each use and replace if chipping or heat discoloration at the tip is observed.