Osg 1739100 Straight Flute Tap 5/16-24 Unf Cobalt

Product Description

The OSG 1739100 is a straight flute machine tap designed to cut 5/16-24 UNF internal threads in a plug chamfer configuration. Built from cobalt high-speed steel with a bright/uncoated finish, it is engineered for use in harder ferrous materials where heat resistance and edge retention are priorities. The tap runs a right-hand thread direction, carries a 3B class of fit with an H3 thread limit, and features 4 flutes for chip clearance in through-hole and shallow blind-hole applications. It is part of OSG Series 305 and is suited for production machining environments where consistent thread quality is required.

This tap is intended for machine tapping operations in shop and production settings. Its cobalt construction makes it appropriate for threading alloy steel, cast iron, die steel, and hardened steel. The plug chamfer — typically 3 to 5 lead threads — allows the tap to start easily in a previously drilled hole and is the most common chamfer style for general-purpose through-hole threading. Machinists and tool-and-die professionals will find this tap suitable for CNC machining centers, drill presses, and tapping arms where a rigid or semi-rigid tapping setup is used.

Key Features

• 5/16-24 UNF thread form with right-hand direction and 3B class of fit
• H3 thread limit for controlled tolerance in precision threading
• Cobalt high-speed steel construction for extended tool life in hard and abrasive ferrous materials
• 4-flute straight flute design provides chip clearance in through-hole applications
• Plug chamfer for easy hole entry and versatile use in through or shallow blind holes
• Bright/uncoated finish — no coating buildup to affect thread tolerance

Compatibility

Rated for use in alloy steel, cast iron, die steel, and hardened steel. Designed for machine tapping operations requiring a 5/16-24 UNF, 3B class of fit, H3 limit straight flute plug tap.

Installation Notes

This tap is intended for installation by machinists and tool-and-die professionals using rigid or floating tapping holders on CNC machining centers, drill presses, or dedicated tapping machines. Ensure the workpiece is securely fixtured and that the tap is properly aligned with the drilled pilot hole before engagement. Use appropriate cutting fluid for the workpiece material to reduce heat buildup and extend tool life. Do not reverse the tap under power without confirming the tapping head supports back-out to avoid breakage in harder materials.