Guhring 9039040063500 Spiral Flute Tap 1/4-20 Unc

Product Description

The GUHRING 9039040063500 is a spiral flute tap designed for blind hole threading in a wide range of metallic workpiece materials. Built from cobalt high-speed steel with a bright/uncoated finish, this tap cuts a 1/4-20 UNC right-hand thread to a 2B class of fit. It runs three flutes in a fast flute style at a 40-degree helix angle, which efficiently evacuates chips upward out of the blind hole during the tapping cycle. The overall length is 2.5 inches, with a shank diameter of 0.255 inches and a square drive size of 0.191 inches. Licensed HVAC, plumbing, and mechanical trades as well as production machinists will find this tap suited to precision tapping applications where chip control is critical.

This tap is sized for 1/4-20 UNC threading and carries a modified bottoming chamfer, allowing it to thread closer to the bottom of a blind hole than a standard plug or taper chamfer tap. It is appropriate for use in aluminum and other non-ferrous metals, gray cast iron, malleable and spheroidal iron, and steel. The 40-degree right-hand spiral flute is particularly effective in softer, long-chipping materials like aluminum where chip packing in a blind hole is a common failure point. The neck length of 1.181 inches provides clearance in deeper hole applications.

Key Features

• 1/4-20 UNC thread form, right-hand thread and right-hand flute direction
• Modified bottoming chamfer for threading near the bottom of blind holes
• 40-degree helix angle fast flute style for efficient upward chip evacuation
• Cobalt HSS construction for improved heat and wear resistance across ferrous and non-ferrous materials
• Bright/uncoated finish suitable for use with standard cutting fluids
• 2B class of fit for standard unified inch thread tolerance requirements

Compatibility

Rated for use in aluminum and other non-ferrous metals, gray cast iron, malleable and spheroidal iron, and steel. Part of GUHRING Series 3904.

Installation Notes

This tap is intended for use by machinists and trade professionals operating drill presses, CNC machining centers, or tapping machines. Always secure the workpiece and ensure the pilot hole diameter is correct for 1/4-20 UNC before tapping. Apply appropriate cutting fluid for the workpiece material to extend tap life and improve thread quality. Do not force a tap that has stopped turning freely — back off and clear chips to avoid breakage in the blind hole.