Osg 1733501 Spiral Flute Tap 1/2-20 Unf 3 Flute Hss

Product Description

The OSG 1733501 is a spiral flute tap designed for threading 1/2-20 UNF internal threads in a range of ferrous materials. Built from vanadium high-speed steel with a steam oxide finish, it provides increased lubricity and resistance to galling during the tapping process. The modified bottoming chamfer allows threading close to the bottom of blind holes while still offering some lead-in guidance. With a 45-degree helix angle, the flutes efficiently evacuate chips up and out of the hole, making this tap well suited for interrupted cuts and deeper blind-hole applications. Licensed machinists, tool and die makers, and maintenance technicians are the typical users.

This tap is rated for use in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel. The 3B class of fit produces threads appropriate for standard commercial fastener assemblies requiring a free-running to close-tolerance engagement. The H3 thread limit designation indicates the tap is ground to produce threads at the upper tolerance range, accounting for slight springback in harder materials. It is well suited for production and job-shop environments where consistent thread quality across multiple setups is required.

Key Features

• 45-degree right-hand spiral flute design evacuates chips upward for clean blind-hole threading
• Modified bottoming chamfer enables threading near the base of blind holes
• Vanadium high-speed steel construction for elevated wear resistance in ferrous materials
• Steam oxide coating reduces friction and improves lubricity during cutting
• H3 thread limit ground for consistent 3B class-of-fit threads in tougher alloys
• Right-hand thread direction, compatible with standard tap handles and CNC tapping cycles

Compatibility

Designed for threading 1/2-20 UNF holes in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Fits standard tap handles and CNC tool holders accepting a 0.367-inch shank diameter.

Installation Notes

Secure the workpiece firmly before tapping and ensure the tap is started square to the drilled hole to avoid thread runout or tap breakage. Apply a suitable cutting fluid or tapping compound rated for the workpiece material, particularly when working in stainless steel. For CNC applications, verify that the spindle tapping cycle matches the 20 threads-per-inch pitch before engaging. Inspect the tap for wear or chipping regularly, and never reverse a broken tap by force.