Osg 1120100 Straight Flute Tap 1/4-20 Unc 4 Flutes Hss

Product Description

The OSG 1120100 is a straight flute tap designed for cutting internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel with a bright, uncoated finish, this plug-chamfer tap produces a 1/4-20 UNC right-hand thread to a 3B class of fit with an H3 thread limit. It features 4 flutes and a thread length of 1 inch within an overall length of 2.5 inches. The plug chamfer provides a gradual lead-in, making it suitable for both through-hole and moderately deep blind-hole applications. Licensed machinists, tool-and-die makers, HVAC fabricators, plumbers, and maintenance technicians commonly reach for this tap in production and repair work.

This tap is suited for tapping operations in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. Its straight flute geometry works well in through-holes and short chip-producing materials where flute evacuation is manageable. The 1/4-20 UNC thread form is one of the most common fastener sizes in residential and light commercial mechanical and HVAC assemblies, making this tap a frequent shop and field tool.

Key Features

• 1/4-20 UNC thread form, right-hand, 3B class of fit with H3 thread limit for consistent tolerance control
• 4 straight flutes for stability and cutting performance in short-chip materials
• Plug chamfer (3-5 thread lead-in) suitable for through-holes and moderately deep blind holes
• High-speed steel construction provides toughness across a broad range of workpiece materials
• Bright, uncoated finish - no additional coating buildup that could affect thread tolerance on close-fit applications
• Compact 2.5-inch overall length fits standard tap handles and CNC tapping chucks

Compatibility

Designed for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces requiring a 1/4-20 UNC internal thread to a 3B class of fit. Part of OSG Series 101.

Installation Notes

Use in a tap wrench, tapping stand, or CNC rigid-tapping setup with appropriate cutting fluid for the workpiece material. Ensure the tap is started perpendicular to the work surface to avoid cross-threading and tap breakage. For blind holes, track depth carefully to prevent bottoming out. Always secure the workpiece before tapping and follow applicable shop safety practices.