Osg 1170501 Straight Flute Tap 1/4-28 Unf Bottoming Hss

Product Description

The OSG 1170501 is a straight flute bottoming tap designed for cutting 1/4-28 UNF internal threads in a range of ferrous and non-ferrous materials. It is manufactured from high-speed steel with an oxide coating that reduces friction and helps extend tool life in production and maintenance threading operations. The tap features 3 straight flutes, a 3B class of fit, and an H3 thread limit, making it suitable for close-tolerance threaded holes where thread form accuracy matters. With an overall length of 2.5 inches and a 1-inch thread length, this tap is sized for standard hand or machine tapping setups. Machinists, tool and die makers, and maintenance technicians are the primary users.

This tap is well suited for threading blind holes to near-full depth, which is the primary advantage of the bottoming chamfer style. It is commonly used in job shop and production environments when tapping aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. It works in both hand tapping and machine tapping setups where the final threading pass must reach close to the bottom of a drilled hole. It belongs to OSG Series 103 and carries no coolant-through feature, so flood or mist coolant is applied externally when used on CNC equipment.

Key Features

• Bottoming chamfer style for threading blind holes to near-full depth
• 1/4-28 UNF thread form with 3B class of fit and H3 thread limit for close-tolerance applications
• High-speed steel construction provides toughness across a range of workpiece materials
• Oxide coating reduces friction and improves chip flow during cutting
• 3 straight flutes suited for short-chipping materials such as cast iron and aluminum
• Right-hand thread direction; compatible with standard tapping heads and tap handles

Compatibility

Designed as a standard replacement straight flute bottoming tap for 1/4-28 UNF threading applications in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. Part of OSG Series 103.

Installation Notes

A licensed machinist or qualified maintenance technician should select the correct tap drill size for the 1/4-28 UNF thread form before use. Power down and secure the workpiece fully before tapping operations begin. For blind-hole applications, use a plug or taper tap first to start the thread, then finish with this bottoming tap to maximize thread depth. Apply an appropriate cutting fluid or tapping compound to extend tool life and improve thread finish.