Osg 1135502 Straight Flute Tap 7/8-9 Unc Plug Hss

Product Description

The OSG 1135502 is a straight flute tap designed to cut 7/8-9 UNC internal threads in a wide range of ferrous and non-ferrous metals. Built from high-speed steel, this tap features a plug chamfer for general through-hole and blind-hole threading applications. It runs 4 flutes with an H4 thread limit, a thread length of 2-7/32 inches, and an overall length of 4-11/16 inches. The right-hand thread direction and 3B class of fit make it a standard choice for precision thread-cutting in production and maintenance machining environments. OSG Series 101 construction ensures consistent tolerance performance across repeated use.

This tap is suited for production shops, tool rooms, and maintenance facilities tackling threading operations in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer style provides a gradual lead-in, making it appropriate for both through-holes and moderately deep blind holes where partial thread engagement at the bottom is acceptable. It is commonly used with a tapping head, drill press, CNC machining center, or manual tap wrench depending on the application volume and tolerance requirements.

Key Features

• 7/8-9 UNC thread form with 3B class of fit for standard precision internal threading
• 4-flute straight configuration channels chips effectively in short-chipping materials
• Plug chamfer with 3-5 thread lead-in suits both through-holes and blind holes
• H4 thread limit provides controlled oversize tolerance for tap wear compensation
• High-speed steel construction withstands the heat generated in steel and cast iron tapping
• Right-hand thread direction compatible with standard tapping equipment and tap handles

Compatibility

Designed for tapping 7/8-9 UNC threads in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Fits standard 7/8-inch tap holders and collet chucks sized for the shank of OSG Series 101 taps.

Installation Notes

This tap is installed and operated by a machinist or toolmaker using a tapping head, CNC rigid tapping cycle, drill press with floating holder, or manual tap wrench. Ensure the workpiece is securely fixtured and the tap is aligned axially with the drilled hole before engagement. Apply appropriate cutting fluid for the workpiece material - sulfurized oil for steels, kerosene or light oil for aluminum - to extend tap life and improve thread finish. Never force a tap that has stopped turning; back out, clear chips, and re-engage to avoid breakage.