Osg 1295301 Extension Tap 3/8-16 Hss Spiral Point

Product Description

The OSG 1295301 is a spiral point extension tap designed for right-hand threading in ferrous and non-ferrous materials. Built from high-speed steel with a steam oxide finish, this tap cuts 3/8-16 UNC threads and delivers a Class 3B fit tolerance. The H3 thread limit provides consistent dimensional control across production runs. At 6 inches overall length with a 1-1/4 inch thread length, the extended reach makes it well suited for threading holes in recessed or deep-access locations that standard-length taps cannot reach. Three flutes and a plug chamfer entry help the tap start squarely and advance chips ahead of the cut. Licensed machinists and tool-and-die professionals are the primary users.

This tap is used in production and maintenance machining environments where UNC 3/8-16 threads are required in materials such as cast iron, aluminum castings, aluminum, and carbon steel. The spiral point design pushes chips forward rather than packing them behind the tap, making it a practical choice for through-hole threading operations on CNC machines, lathes, or manual tapping setups. The extension length adds utility on fixture work, engine block applications, and assemblies where the workpiece depth or surrounding structure limits access.

Key Features

• 3/8-16 UNC thread form, Class 3B fit for controlled tolerance threading
• H3 thread limit provides consistent oversize compensation for plated or tight-tolerance applications
• Spiral point geometry pushes chips forward, designed for through-hole operations
• 6 inch overall length with reduced shank allows reach into deep or recessed bores
• Steam oxide finish improves lubrication retention and reduces galling
• High-speed steel construction suited for cast iron, aluminum, and carbon steel

Compatibility

Designed for threading 3/8-16 UNC through-holes in cast iron, aluminum castings, aluminum, and carbon steel. Part of OSG Series 917 extension taps.

Installation Notes

Tap installation should be performed by a qualified machinist following standard threading procedures. Always apply appropriate cutting fluid for the workpiece material to extend tap life and improve thread quality. Secure the workpiece firmly before tapping to prevent movement that can break the tap or produce off-axis threads. When using with power equipment, set torque or feed limits appropriate to the tap diameter to avoid breakage.