Guhring 9039880063500 Cobalt Sti Tap 1/4-20 Unc

Product Description

The GUHRING 9039880063500 is a cobalt spiral flute STI (Screw Thread Insert) tap designed for cutting internal threads in demanding materials. Built to a 1/4-20 UNC thread standard with a 3B class of fit, this tap features a 40-degree right-hand helix and a modified bottoming chamfer for threading close to the bottom of blind holes. A TiN (Titanium Nitride) finish increases surface hardness and reduces friction during cutting. With an overall length of 2.72 inches and a shank diameter of 0.318 inches, it fits standard tap holders used in machine shop and maintenance applications. Three flutes provide efficient chip evacuation in the materials this tool targets.

This tap is suited for threading alloy steel and unalloyed steel where a Screw Thread Insert is required to create a stronger or repaired thread. The modified bottoming chamfer makes it appropriate for shallow blind-hole applications where a standard taper or plug chamfer cannot reach full thread depth. It belongs to GUHRING Series 3988 and is intended for use by machinists, maintenance technicians, and tool-and-die professionals working in production or repair environments. Right-hand flute direction is standard for conventional right-hand threading operations on manual or CNC tapping equipment.

Key Features

• 1/4-20 UNC thread form with 3B class of fit for STI applications
• 40-degree right-hand spiral flute for efficient chip evacuation in steel
• Modified bottoming chamfer allows threading closer to the bottom of blind holes
• Cobalt construction provides heat and wear resistance in alloy and unalloyed steel
• TiN finish reduces cutting friction and extends tool life
• 3-flute design balances chip flow and cutting load at this diameter

Compatibility

Designed for use in alloy steel and unalloyed steel workpieces requiring a 1/4-20 UNC STI thread. Compatible with standard 0.318-inch shank tap holders and collet systems on manual tapping arms and CNC machining centers.

Installation Notes

Installation and use of this tap should be performed by a qualified machinist or maintenance technician familiar with tapping operations. Ensure the workpiece is properly secured and the correct STI tap drill size is used before tapping. Apply appropriate cutting fluid for steel to reduce heat buildup and extend tool life. Never reverse a spiral flute tap under power without confirming the machine or tool holder supports reversing cycles.