Osg 1136105 Straight Flute Tap 1-8 Unc Plug 3B Tin Hss

Product Description

The OSG 1136105 is a straight flute tap designed to cut 1-8 UNC internal threads in a wide range of ferrous and non-ferrous workpiece materials. Built from high-speed steel (HSS) and finished with a titanium nitride (TiN) coating, it delivers extended tool life and reduced friction during tapping operations. The plug chamfer on the leading end — typically 3 to 5 threads — allows entry in through-holes and semi-blind applications. With a thread limit of H4 and a 3B class of fit, this tap produces threads with the tolerance range required for general-purpose fastener assemblies. Machinists and maintenance technicians working in job shops, production environments, or MRO applications will find this tap suited to standard CNC and manual tapping setups.

This tap is designed for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The 1-8 UNC designation makes it appropriate for tapping holes that accept large-diameter unified coarse-pitch fasteners commonly found in structural, mechanical, and industrial assemblies. The straight flute design works best in through-hole and short blind-hole applications where chips can fall away freely from the cutting zone. It is part of OSG Series 101, a line of standard-geometry HSS taps for general-purpose threading work.

Key Features

• 1-8 UNC thread form with right-hand thread direction for standard fastener compatibility
• TiN coating extends cutting edge life and reduces built-up edge on aluminum and steel
• Plug chamfer (3-5 thread lead) suits through-hole and semi-blind tapping
• 3B class of fit and H4 thread limit for general-purpose tolerance control
• 4 straight flutes for chip clearance in short to medium blind-hole depths
• Coolant-through feature not required — compatible with flood or manual lubrication

Compatibility

Rated for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. This tap is an OSG Series 101 standard-geometry HSS tap intended for general-purpose 1-8 UNC thread production on compatible CNC machining centers, drill presses, and tapping machines with appropriate tap holders.

Installation Notes

Installation should be performed by a qualified machinist familiar with tapping speeds, feeds, and proper tap holder selection for the machine type in use. Always ensure the workpiece is securely fixtured and the pilot hole is drilled to the correct tap drill diameter for a 1-8 UNC thread before beginning the tapping cycle. Use a cutting fluid or tapping compound appropriate for the workpiece material to prevent galling and premature tool wear. Inspect the tap for wear or chipping before each use and replace if thread quality degrades.