Osg 1138600 Straight Flute Tap 1-3/8-12 Unf Bottoming Hss

Product Description

The OSG 1138600 is a straight flute bottoming tap designed to cut 1-3/8-12 UNF internal threads in a range of ferrous and non-ferrous metals. Built from high-speed steel (HSS) with a bright/uncoated finish, this tap delivers consistent thread form in through-holes and blind holes where full thread engagement close to the bottom of the bore is required. With 6 flutes, an H4 thread limit, and a 3B class of fit, the 1138600 is suited for precision threading work performed by machinists and maintenance technicians in industrial and manufacturing environments.

This tap is used in applications involving aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. The bottoming chamfer style makes it appropriate for blind-hole threading where the usable thread depth must extend as close to the bottom as possible. It is commonly specified for production runs and repair work in machine shops, tool rooms, and maintenance departments where tight thread tolerances are required.

Key Features

• 1-3/8-12 UNF thread form with 3B class of fit for standard precision thread engagement
• Bottoming chamfer for threading close to the bottom of blind holes
• 6 flutes for improved chip distribution and stability in the cut
• H4 thread limit for consistent oversize tolerance control
• High-speed steel construction with bright/uncoated finish - no coating to interfere with chip flow in softer materials
• Right-hand thread direction, Series 101
• No coolant-through - compatible with flood coolant or hand-tapping lubricant applied externally

Compatibility

Designed for threading aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Cuts 1-3/8-12 UNF right-hand internal threads per OSG Series 101 specifications.

Installation Notes

Installation is performed by machinists or maintenance technicians using a tap wrench, tapping head, or CNC/manual machine tool. Power down or disengage the machine spindle before loading the tap and verify the pilot hole diameter matches the recommended drill size for 1-3/8-12 UNF before beginning. Apply a suitable cutting fluid or tapping oil for the workpiece material to extend tool life and improve thread finish. Bottoming taps require that the hole first be chamfered with a plug or taper tap to establish the thread before the bottoming tap finishes to depth.