Chicago-latrobe 48921 Screw Machine Drill Bit 21/64 in Hss

Product Description

The CHICAGO-LATROBE 48921 is a screw machine length drill bit designed for general-purpose drilling in a wide range of materials. Built from high-speed steel (HSS) with a bright/uncoated finish, it features a 21/64-inch (0.3281-inch) diameter and a left-hand cutting direction, making it suited for applications that require reverse-rotation drilling. The 118-degree standard point angle and web-thinned tip promote clean entry and reduce walking on start. Overall length is 2-15/16 inches, keeping the bit compact and rigid for short-reach drilling tasks. This bit is used by machinists, maintenance technicians, and trade professionals working with non-ferrous metals, plastics, and wood.

The 48921 fits into standard drill chucks and CNC machine spindles accepting straight-shank tooling at 0.3281 inches (8.33 mm) shank diameter. Its screw machine length design provides extra rigidity compared to jobber-length bits, which reduces deflection in close-tolerance or repetitive production drilling. Primary workpiece materials listed by the manufacturer include aluminum, copper, magnesium, slate, thermoplastic, and wood. The 1-11/16-inch flute length handles moderate chip evacuation needs in shallow-to-medium depth holes. Series 157L denotes the left-hand orientation within the CHICAGO-LATROBE product line.

Key Features

• Left-hand cutting direction for reverse-rotation drilling and broken-fastener extraction applications
• HSS construction with bright/uncoated finish for use in non-ferrous metals, plastics, and wood
• Web-thinned, parallel-web tip geometry reduces thrust and improves point centering
• Screw machine length body provides increased rigidity and reduced deflection versus jobber-length bits
• Straight shank at 0.3281 inches diameter fits standard drill chucks and collet holders
• Manufactured to ISO standards with a diameter tolerance of +0.0000 to -0.0010 inches

Compatibility

Designed as a general-purpose replacement or production drill bit for use in any standard straight-shank drill chuck or collet system accepting a 0.3281-inch shank. Suitable for benchtop drill presses, hand drills, and CNC drilling operations targeting aluminum, copper, magnesium, slate, thermoplastic, and wood workpieces.

Installation Notes

Install and remove drill bits with the machine fully powered off and the spindle at a complete stop. Secure the straight shank firmly in the chuck or collet to the full depth of the shank before tightening. Left-hand bits require the drill or machine to be set to reverse rotation to cut; confirm spindle direction before engaging the workpiece. Inspect the cutting edges and point geometry before each use and replace the bit if chipping or excessive wear is present.