Osg 1745000 Straight Flute Tap 4-40 Unc Cobalt

Product Description

The OSG 1745000 is a straight flute machine tap designed for cutting 4-40 UNC internal threads in a range of ferrous materials. It features a plug chamfer, three flutes, and is manufactured from cobalt high-speed steel with a bright, uncoated finish. The plug chamfer allows the tap to start easily in through-holes or blind holes with adequate clearance. Overall length is 1.875 inches, with a thread length of 0.5625 inches (9/16 inches). The H2 thread limit provides a standard tolerance range suited to general-purpose 2B class of fit threading. This tap is intended for use by machinists, tool and die makers, and maintenance technicians working with small-diameter threaded fastener applications.

This tap is suited for threading in alloy steel, cast iron, die steel, and hardened steel workpieces where a 4-40 UNC thread form is required. The cobalt construction improves heat and wear resistance compared to standard high-speed steel, making it appropriate for harder or more abrasive materials. Typical applications include small machine components, instrument hardware, and precision assemblies that use 4-40 fasteners. It is a right-hand tap and cuts in the standard clockwise direction. The tap is used in both manual tapping handles and machine tapping operations on drill presses, CNC machining centers, and tapping machines.

Key Features

• Cobalt high-speed steel construction for improved heat resistance and tool life in harder materials
• Plug chamfer (approximately 3-5 thread lead) for easy starting in through-holes and adequate-depth blind holes
• 3-flute straight flute geometry provides chip clearance in short, broken chip materials such as cast iron and hardened steel
• H2 thread limit for standard 2B class of fit tolerances
• Bright, uncoated finish — no coating buildup affects thread form or dimensional accuracy
• Right-hand thread direction, compatible with standard tapping equipment and holders

Compatibility

Designed as an OEM-style machine tap for use with standard tapping drivers, T-handle tap wrenches, and machine tap holders sized for the 0.141-inch shank diameter common to 4-40 series taps.

Installation Notes

This tap is installed and operated by machinists or maintenance technicians using appropriate tapping equipment. Always ensure the workpiece is securely fixtured and the tap is aligned perpendicular to the hole before starting. Use a cutting fluid appropriate for the workpiece material to reduce heat and extend tool life. Do not force the tap if resistance increases unexpectedly, as small-diameter taps are susceptible to breakage under torsional overload.