Osg 1770801 Spiral Flute Tap 3/4-10 Unc 4 Flutes

Product Description

The OSG 1770801 is a spiral flute tap designed for threading 3/4-10 UNC holes in difficult-to-machine materials. It features a modified bottoming chamfer, a 2B class of fit, and an H3 thread limit, giving machinists precise control over thread tolerance. The powdered metal construction and steam oxide coating improve wear resistance and reduce friction during cutting. With 4 right-hand spiral flutes at a 10-degree helix angle, the tap efficiently evacuates chips upward through the flute — a key advantage in blind-hole applications. Licensed machinists and toolroom technicians typically specify this tap when threading stainless steel, hardened steel, titanium, or high-nickel alloys.

This tap is suited for production and maintenance machining environments where blind holes in tough alloys require a clean, accurate thread. The spiral flute design makes it particularly effective in CNC machining centers and manual knee mills where chip evacuation out of the hole is necessary to prevent re-cutting and tap breakage. It is part of the OSG Series 313NI line, which targets high-nickel alloy and stainless steel applications. No coolant-through capability is built in, so external or flood coolant should be applied at the cutting zone during use.

Key Features

• 3/4-10 UNC thread form with H3 thread limit for controlled 2B class of fit
• Modified bottoming chamfer for threading close to the bottom of blind holes
• Spiral flute geometry at 10-degree helix angle promotes chip ejection from blind holes
• Powdered metal substrate with steam oxide coating for extended tool life in hard materials
• Right-hand flute direction, right-hand thread — compatible with standard CNC and manual spindle rotation
• No coolant-through design; suitable for use with external flood or mist coolant

Compatibility

Rated for material applications including stainless steel, hardened steel, titanium, and high-nickel alloy. Part of the OSG Series 313NI tap line.

Installation Notes

Installation should be performed by a qualified machinist following established tapping procedures. Power down and lock out the machine spindle before changing tooling. Use a properly sized tap holder or floating tap collet to reduce the risk of tap breakage, and apply appropriate cutting fluid continuously at the cutting edge throughout the operation. Always verify pilot hole diameter against the 3/4-10 UNC tap drill chart before threading.