Osg 1824000 Spiral Point Sti Tap 4-40 Unc 2 Flute Hss

Product Description

The OSG 1824000 is a spiral point STI tap designed for cutting 4-40 UNC threads in a plug chamfer style. Built from high-speed steel (HSS) with a bright, uncoated finish, this tap is suited for general-purpose tapping operations where an STI (Screw Thread Insert) thread form is required. The plug chamfer distributes cutting load gradually across the lead threads, making it appropriate for through-hole applications. At 1-7/8 inches overall length with a 9/16-inch thread length, this is a compact tool for use in small-diameter tapping work. Machinists, maintenance technicians, and toolroom professionals install this tap by hand or with a machine tapper in ferrous and non-ferrous materials.

This tap is used in applications requiring STI thread forms, typically to prepare holes that will accept Heli-Coil or similar wire thread inserts. The 4-40 UNC thread designation suits fine-thread, small-fastener work common in electronics assembly, instrument manufacturing, precision machining, and light mechanical repair. The spiral point geometry pushes chips forward ahead of the tap, making it effective in through-hole setups where chip evacuation is not obstructed. It is appropriate for both manual and low-speed machine tapping setups.

Key Features

• STI thread form for use with wire thread inserts such as Heli-Coil style inserts
• Spiral point design pushes chips forward, optimized for through-hole tapping
• High-speed steel construction provides durability across a range of workpiece materials
• Plug chamfer distributes cutting load over several lead threads for controlled entry
• H2 thread limit for close-tolerance thread production
• Bright, uncoated finish suitable for use with cutting fluid in general-purpose tapping

Compatibility

Designed as an OEM-style replacement or standard toolroom tap for applications requiring a 4-40 UNC STI thread form. Fits standard tap holders and wrenches sized for a 0.141-inch shank diameter.

Installation Notes

Installation is performed by qualified machinists or maintenance technicians using a calibrated tap wrench or machine tapper. The workpiece must be secured and the correct STI drill size must be used before tapping to achieve proper thread engagement. Apply a suitable cutting fluid for the workpiece material to extend tool life and improve thread quality. Avoid forcing the tap or reversing too aggressively, as small-diameter taps are susceptible to breakage under side load.