Chicago-latrobe 48255 Screw Machine Drill Bit Hss

Product Description

The CHICAGO-LATROBE 48255 is a screw machine length drill bit sized at 0.397 inches (Letter Size X) and built from high speed steel with a coated finish. The stub-length body fits short-travel drill presses and screw machines where standard-length bits would overhang the work. The 135-degree split point reduces walking at entry and lowers thrust force, making it well suited for production drilling in cast iron and steel. Two spiral flutes with regular helix evacuate chips consistently, and the web-thinned, parallel-web construction keeps the cutting geometry stable through the full hole depth. This bit meets NAS 907 and ISO standards and is rated for heavy-duty service.

This bit is designed for drilling cast iron and steel in production and job-shop environments. The straight-cylindrical shank seats in standard drill chucks, collets, and quick-change toolholders without modification. The screw machine length, at 3.3125 inches overall with a 1.9375-inch flute, is the right choice when minimizing runout and maximizing rigidity matter more than hole depth. Typical install settings include CNC drill presses, turret lathes, screw machines, and bench-top drill presses used in fabrication and maintenance shops.

Key Features

• Letter Size X (0.397 inches) diameter with a tight tolerance of +0.0000 to -0.0010 inches
• 135-degree split point reduces thrust and prevents walking on hard materials
• Web-thinned, parallel-web construction maintains cutting stability
• High speed steel construction with coated finish for extended tool life on steel and cast iron
• Screw machine (stub) length provides maximum rigidity in short-travel setups
• Meets NAS 907 (NAS designation) and ISO standards for heavy-duty drilling

Compatibility

Designed as an OEM-style replacement or direct substitute for screw machine length drill bits in the 0.3500 to 0.4000 inch diameter range, Series 2159. Fits any standard straight-shank drill chuck or collet rated for the 0.397-inch shank diameter.

Installation Notes

A qualified machinist or maintenance technician should install and operate this bit using a properly rated drill press, lathe, or screw machine. Secure the straight-cylindrical shank fully in the chuck or collet before applying power, and confirm runout is within acceptable limits before beginning production drilling. Power down and de-energize the machine before changing bits or clearing chips. Do not exceed the recommended surface footage for high speed steel when drilling hardened steels or abrasive cast irons.