Hertel 42192 Screw Machine Drill Bit 0.25 in Cobalt

Product Description

The HERTEL 42192 is a screw machine length (stub-length) drill bit designed for drilling into tough workpiece materials where rigidity and cutting performance matter. Ground from M35 cobalt high-speed steel, this 0.25-inch diameter bit carries an oxide straw finish that provides mild lubricity and corrosion resistance during cutting. The 135-degree split point reduces walking and requires no center punch on flat or curved surfaces. At 2.5 inches overall length with a 1.375-inch spiral flute, it fits standard drill chucks and is well-suited for use in drill presses, CNC machining centers, and hand-held power drills. Machinists, tool-and-die workers, and maintenance technicians reach for cobalt stub-length bits when carbon or HSS tooling fails in hardened stock.

This bit is rated for hardened materials, heat-treatable alloyed steels, stainless steel, and titanium alloys — workpiece categories that quickly degrade standard HSS tooling. The screw machine length format provides a shorter, stiffer cutting profile than jobber-length bits, reducing deflection and improving hole location accuracy in tight setups or when working close to a fixture. The 3xD flute-to-diameter ratio supports chip evacuation in short-depth holes without coolant-through capability, making it practical for general shop use where flood or through-spindle coolant is not available.

Key Features

• M35 cobalt HSS construction for heat resistance and edge retention in hard alloys
• 135-degree split point reduces thrust force and eliminates center-punch requirement
• Oxide straw finish provides mild lubricity and light corrosion protection
• Stub screw machine length (2.5 inches overall) adds rigidity and reduces deflection
• Regular spiral flute with 3xD ratio supports efficient chip clearing in short-depth bores
• No coolant-through requirement — compatible with standard shop drilling setups

Compatibility

Designed as a standard 0.25-inch shank screw machine length drill bit compatible with any drill chuck or collet accepting a 0.25-inch round shank, including drill presses, milling machines, and hand-held power drills.

Installation Notes

A licensed machinist or qualified maintenance technician should select appropriate spindle speed and feed rate based on workpiece material hardness before drilling. Secure the workpiece firmly in a vise or fixture to prevent movement during cutting. When drilling stainless steel or titanium alloys, use a cutting fluid or tapping oil to extend tool life and improve finish quality. Inspect the cutting edges before each use and replace the bit if chipping or excessive wear is observed.