Osg 2858001 Spiral Point Tap 5/8-18 Unf 3 Flute Plug

Product Description

The OSG 2858001 is a spiral point plug tap designed for threading 5/8-18 UNF right-hand internal threads in through-hole applications. Built from 3% vanadium high-speed steel (HSS-E) with a steam oxide coating, it delivers improved lubricity and corrosion resistance compared to uncoated tooling. The plug chamfer - typically 3 to 5 threads - allows the tap to start easily in a pre-drilled hole and drive chips forward, ahead of the cutting edge. With a 1.91-inch thread length and 3.811-inch overall length, this tap is suited for production threading in machine tool setups as well as bench work by skilled machinists and toolroom technicians.

This tap is used in threading operations across a wide range of ferrous and non-ferrous materials, including aluminum, low-carbon steel, medium-carbon steel, high-carbon steel, alloy steel, die steel, cast iron, and stainless steel. Its spiral point geometry pushes chips ahead of the tap, making it best suited for through-hole applications rather than blind holes. It carries a thread limit designation of H7, indicating an oversize tolerance class appropriate for situations where coated fasteners or specific fit requirements demand additional clearance. This tap is a standard choice for job shops, maintenance facilities, and production environments running threaded fastener or fitting work.

Key Features

• 5/8-18 UNF thread form, right-hand, H7 thread limit with oversize designation
• 3% vanadium HSS-E construction for improved wear resistance over standard M2 HSS
• Steam oxide coating reduces friction and provides mild corrosion protection
• Spiral point geometry drives chips forward - optimized for through-hole threading
• 3 flutes with plug chamfer for positive starting and balanced cutting action
• Compatible with a wide range of workpiece materials including stainless and alloy steels

Compatibility

Designed for through-hole tapping in materials including aluminum, cast iron, low-, medium-, and high-carbon steel, alloy steel, die steel, and stainless steel. Thread limit H7 with oversize classification suits applications requiring additional thread clearance.

Installation Notes

This tap should be installed in a tap holder, floating tap adapter, or rigid tapping chuck appropriate for the machine tool in use. Ensure the workpiece hole is drilled to the correct tap drill diameter for a 5/8-18 UNF thread before beginning. Apply a suitable cutting fluid for the workpiece material - sulfurized oil for steels, water-soluble coolant or kerosene for aluminum. Inspect the tap for wear or chip packing between uses, and never force a tap that has stopped advancing under normal feed pressure.