Chicago-latrobe 48931 31/64 Inch Hss Screw Machine Drill Bit

Product Description

The CHICAGO-LATROBE 48931 is a screw machine length drill bit designed for controlled, short-reach drilling in production and maintenance environments. Built from high-speed steel (HSS) with a bright, uncoated finish, it features a 31/64 inch (0.4844 inch) diameter, a standard 118-degree point angle, and a left-hand cutting direction. The shorter overall length of 3-11/16 inches improves rigidity and reduces deflection compared to jobber-length bits, making it a go-to choice for tight-clearance or high-volume drilling applications. A web-thinned geometry at the tip lowers thrust requirements and improves penetration into the workpiece.

This bit is suited for general-purpose drilling in non-ferrous metals, plastics, and soft materials. Primary workpiece materials listed by the manufacturer include aluminum, copper, magnesium, slate, thermoplastic, and wood. The straight shank fits standard drill chucks on benchtop drill presses, hand-held power drills, and CNC or screw machine setups. It is appropriate for use by machinists, electricians, plumbers, HVAC technicians, and general tradespeople who need a compact, stout bit for precise hole placement.

Key Features

• Left-hand cutting direction — useful for backing out broken fasteners and reverse-rotation setups
• HSS construction provides heat resistance for general-purpose metal and non-metal drilling
• Web-thinned tip reduces entry thrust and improves point accuracy
• Screw machine length (3-11/16 inches OAL) delivers extra rigidity versus standard jobber-length bits
• Regular spiral flute with parallel web configuration promotes consistent chip evacuation
• Bright, uncoated finish compatible with cutting fluids and light dry drilling

Compatibility

Designed for use in standard straight-shank drill chucks and screw machine applications. Suitable for drilling aluminum, copper, magnesium, slate, thermoplastic, and wood as specified by the manufacturer. Part of the CHICAGO-LATROBE Series 157L left-hand screw machine drill line.

Installation Notes

Installation and use should follow standard machining safety practices — secure the workpiece firmly before drilling and ensure the chuck is fully tightened on the straight shank. Because this bit has a left-hand cut, it must be used in a reverse-rotation spindle to cut; running it in standard forward rotation will not produce a cutting action. When drilling metals such as copper or aluminum, apply an appropriate cutting fluid to extend tool life and improve hole finish. Inspect the cutting edges before each use and replace the bit if chipping or dulling is observed.