Guhring 9039850063500 Spiral Flute Tap 1/4-28 Cobalt Tin

Product Description

The GUHRING 9039850063500 is a spiral flute tap designed for blind hole threading in alloyed and unalloyed steel. Part of the Series 3985 line, it features a 40-degree helix angle and a modified bottoming chamfer that allows threading close to the bottom of a blind hole with minimal runout. The cutting geometry is produced from cobalt high-speed steel for added heat and wear resistance, and a TiN coating reduces friction at the cutting edge. Overall length is 2.5 inches. This tap is suited for machinists, toolroom technicians, and maintenance professionals working on precision threaded fastener applications.

This tap cuts a 1/4-28 right-hand thread to a UNC/UNF standard at an H11 thread limit, with an oversize allowance of 0.005 inches. The modified bottoming chamfer makes it the correct choice when threading must extend to near the base of a blind bore. The fast flute style clears chips efficiently in the spiral flute design, reducing the need for frequent withdrawal in shorter blind holes. Typical applications include production tapping and repair threading in steel components across manufacturing, maintenance, and industrial assembly environments.

Key Features

• Modified bottoming chamfer for threading close to the bottom of blind holes
• 40-degree helix angle with fast flute style for efficient chip evacuation
• Cobalt HSS construction for improved heat resistance in steel cutting
• TiN coating reduces friction and extends tool life
• H11 thread limit with 0.005 inch oversize for controlled thread fit
• Right-hand flute and right-hand thread direction; no coolant-through required

Compatibility

Designed for blind hole threading in alloyed and unalloyed steel. Cuts a 1/4-28 thread to UNC/UNF standards at H11 class of fit. Verify thread limit and chamfer requirements before installation in other material types.

Installation Notes

This tap is installed by machinists or maintenance technicians using a tap wrench, tapping head, or CNC rigid tapping cycle. Power down or de-energize any machine tool before changing tooling. Use appropriate cutting fluid for steel to maintain edge life and thread quality. Do not force the tap against the bottom of a blind bore beyond its chamfer design limits.