Osg 1725201 Spiral Point Tap 7/8-9 Unc 3 Flute Hss

Product Description

The OSG 1725201 is a spiral point plug tap designed for threading 7/8-9 UNC through-holes in a wide range of ferrous materials. Built from Vanadium High Speed Steel (HSS-E) and finished with a steam oxide coating, this tap resists heat and wear during high-production threading operations. It carries a 3B class of fit and an H4 thread limit, ensuring accurate thread form and consistent dimensional control. The plug chamfer distributes cutting forces across the leading threads for a controlled entry. With a 3-flute configuration, chips are pushed forward ahead of the tap rather than packed into the flute, making it well suited for through-hole applications. Overall length is 4.689 inches with a thread length of 2-7/32 inches (1.389 inches decimal). Licensed machinists, tool-and-die makers, and maintenance mechanics are the primary installers.

This tap is intended for right-hand threading in through-hole configurations. Material application includes hardened steel, low-carbon steel, medium-carbon steel, and stainless steel, covering the most common ferrous workpiece materials encountered in fabrication, maintenance, and production machining environments. The 0.697-inch shank diameter is sized for standard tap holders and floating-head tapping attachments used in manual drill press, CNC, and tapping machine setups. No coolant-through feature is present, so external cutting fluid or tapping oil is recommended when threading stainless or harder steels.

Key Features

• Spiral point geometry pushes chips forward, ideal for through-hole threading
• Vanadium HSS-E construction for improved wear resistance over standard HSS
• Steam oxide coating reduces friction and provides corrosion resistance during storage and use
• H4 thread limit and 3B class of fit for consistent, gauged thread accuracy
• Plug chamfer for controlled entry and reduced torque at start
• Right-hand cut, no interrupted thread, no oversize - standard production geometry

Compatibility

Designed for through-hole tapping of 7/8-9 UNC threads in hardened steel, low-carbon steel, medium-carbon steel, and stainless steel workpieces. Fits standard tap holders accepting a 0.697-inch shank diameter.

Installation Notes

Secure the workpiece and ensure the tap is aligned perpendicular to the drilled hole before beginning the threading operation. Power down or deactivate the machine spindle before loading or removing the tap from the holder. Apply a suitable cutting fluid or tapping oil, particularly when working with stainless steel or harder materials, to prolong tap life and improve thread finish. Inspect the tap for chipping or wear regularly, as a damaged tap can produce undersized threads or seize in the hole.