Osg 1135500 Straight Flute Tap 7/8-9 Unc Plug Hss

Product Description

The OSG 1135500 is a straight flute plug tap designed for creating internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel (HSS) with a bright, uncoated finish, it cuts a 7/8-9 UNC thread in a right-hand direction with a 3B class of fit. The plug chamfer on the lead threads makes it suitable for through-hole and most standard blind-hole applications. With an overall length of 4-11/16 inches and a thread length of 2-7/32 inches, this tap is sized for production and maintenance tapping operations performed by machinists and tool and die tradespeople.

This tap is well suited for tapping operations in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The straight flute geometry is most effective in short-chipping materials where chip evacuation is not a concern. It carries an H4 thread limit designation, indicating a tolerance suitable for 3B fit work. It belongs to OSG Series 101 and is packaged as a single unit, making it appropriate for both production floor and low-volume maintenance environments.

Key Features

• 7/8-9 UNC thread form, right-hand direction, 3B class of fit
• Plug chamfer with 4 flutes for through-hole and standard blind-hole tapping
• High-speed steel construction for durability across a broad material range
• H4 thread limit for consistent 3B tolerance control
• Bright, uncoated finish - no coolant-through; suitable for use with cutting fluid applied externally
• Straight flute geometry optimized for short-chipping materials such as cast iron and carbon steels

Compatibility

Designed for tapping 7/8-9 UNC threads in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. Fits standard tap holders and machines accepting a 0.697-inch shank diameter with a 0.523-inch square drive.

Installation Notes

Installation requires a properly sized drill press, CNC machine, or hand tap wrench rated for the shank diameter. Ensure the workpiece is securely fixtured before starting. Apply appropriate cutting fluid for the material being tapped; this tap does not have coolant-through capability. Follow shop safety practices and wear eye protection when operating tapping equipment.