Osg 1142800 Straight Flute Tap 1/2-20 Unf Plug 2B Hss

Product Description

The OSG 1142800 is a straight flute plug tap designed to cut 1/2-20 UNF internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel with a bright/uncoated finish, this tap delivers consistent thread accuracy at a 2B class of fit with an H5 thread limit, making it suitable for standard-tolerance threading applications. The four-flute straight configuration provides good chip control in through-hole and short blind-hole operations. With an overall length of 3.375 inches and a thread length of approximately 1.656 inches, the 1142800 is sized for general-purpose production and maintenance work performed by machinists, tool-and-die workers, and maintenance technicians.

This tap is appropriate for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer - typically featuring a 3 to 5 thread lead - makes it a practical choice for through-hole threading and for starting threads in blind holes where sufficient thread runout is present. It suits both manual tapping with a tap wrench and machine tapping on drill presses, CNC machining centers, and manual mills running at appropriate spindle speeds for the material and thread size.

Key Features

• 1/2-20 UNF right-hand thread profile with 2B class of fit for standard tolerance assemblies
• H5 thread limit for controlled oversize to account for material springback
• Four straight flutes suited for through-hole and short blind-hole tapping
• Plug chamfer for general-purpose thread starting and production threading
• High-speed steel construction handles a broad range of workpiece materials including cast iron and carbon steels
• Bright/uncoated finish - no additional coating variables affecting thread dimension

Compatibility

Designed for use in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces requiring a 1/2-20 UNF internal thread. Part of OSG Series 101.

Installation Notes

Tapping should be performed by a qualified machinist or maintenance technician using a properly aligned tap wrench, tapping head, or rigid machine spindle. Apply appropriate cutting fluid or tapping compound for the workpiece material - dry tapping in steel will accelerate tool wear and risk tap breakage. Ensure the workpiece is securely fixtured and the tap is started square to the hole before applying feed pressure. Always back the tap out periodically to clear chips when working in deeper holes.