Osg 1590100 Straight Flute Tap 1/4-20 Unc Hss Plug

Product Description

The OSG 1590100 is a straight flute plug tap designed for cutting 1/4-20 UNC internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel with a bright, uncoated finish, it features 4 flutes and a plug chamfer that balances thread starting ease with efficient chip evacuation. The H11 thread limit indicates a slightly oversized tolerance — 0.005 inches oversize — which compensates for material springback and helps achieve a proper fit in finished threads. Overall length is 2.5 inches with a thread length of approximately 0.748 inches. This tap is intended for use in machine tapping and hand tapping operations by machinists, maintenance technicians, and industrial tradespeople.

The OSG 1590100 is suited for through-hole and blind-hole tapping in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer style — typically 3 to 5 threads of lead — makes it the standard choice for most general-purpose tapping where the tap can enter from the open end of a through hole or where adequate thread clearance exists in a blind hole. It is commonly used in production tapping setups and maintenance repair operations across manufacturing, HVAC equipment fabrication, and mechanical assembly environments.

Key Features

• 1/4-20 UNC thread form with right-hand thread direction
• 4-flute straight flute design for chip clearance in short-chipping materials
• Plug chamfer provides a balanced lead for through-hole and most blind-hole applications
• H11 thread limit with 0.005 inches oversize for accurate finished thread fit
• High-speed steel construction handles a broad range of ferrous and non-ferrous workpiece materials
• Bright, uncoated finish — no coating buildup concerns in light-duty or intermittent use

Compatibility

Designed for tapping 1/4-20 UNC threads in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. Part of the OSG 101H series.

Installation Notes

Install in a standard tap wrench, tapping fixture, or machine spindle with appropriate tap chuck. Ensure the workpiece is securely fixtured and the pilot hole is drilled to the correct tap drill diameter for 1/4-20 UNC threads before beginning. Apply cutting fluid appropriate to the workpiece material to extend tool life and improve thread finish. Never force a tap against resistance — back off periodically to break chips and prevent tap breakage.