Osg 1715801 Spiral Flute Sti Tap 4-40 Unc Powdered Metal

Product Description

The OSG 1715801 is a spiral flute STI (Screw Thread Insert) tap designed for cutting 4-40 UNC internal threads in demanding materials. Built from powdered metal with a steam oxide finish, this tap handles alloy steel, die steel, hardened steel, high-nickel alloy, stainless steel, and titanium. It features a 2-flute right-hand spiral design with a 15-degree helix angle and a modified bottoming chamfer, which allows threading close to the bottom of blind holes. The overall length is 1-7/8 inches with a shank diameter of 0.141 inches and a thread length of 9/16 inches. This tool is used by machinists, tool and die makers, and precision manufacturers working on threaded insert applications.

This tap is suited for STI thread insert applications requiring a 4-40 UNC thread form. The modified bottoming chamfer makes it appropriate for shallow or bottom-of-hole threading where a standard taper chamfer would leave insufficient thread engagement. Material compatibility spans a wide range of ferrous and high-strength alloys, making it a practical choice for aerospace, medical device, and industrial manufacturing environments where insert-style thread repair or original thread creation is required. OSG Series 315 identifies this as part of a tooling family built for high-performance threading in difficult-to-machine materials.

Key Features

• 4-40 UNC thread form at 40 threads per inch for fine-pitch STI applications
• Powdered metal construction provides increased wear resistance and toughness over standard HSS
• Steam oxide finish reduces friction and provides mild corrosion resistance during storage and use
• 15-degree right-hand helix promotes upward chip evacuation, reducing chip packing in blind holes
• Modified bottoming chamfer allows threading closer to the bottom of blind holes than a plug chamfer
• H2 thread limit for controlled tolerance fits in threaded insert applications

Compatibility

Designed for use in alloy steel, die steel, hardened steel, high-nickel alloy, stainless steel, and titanium workpieces requiring 4-40 UNC STI threads. Part of OSG Series 315.

Installation Notes

This tap should be installed in a tap holder or CNC rigid tapping chuck appropriate for the 0.141-inch shank diameter. Always ensure the workpiece is securely fixtured and the spindle is properly aligned before tapping to prevent tap breakage in hard materials. Use cutting fluid rated for the specific workpiece material, particularly when threading stainless steel, titanium, or high-nickel alloys. Inspect the tap for wear or chipping before each use, as small-diameter taps in hard materials are susceptible to breakage if operated with worn cutting edges.