Osg 2940201 Spiral Flute Tap 1/4-20 Unc Modified Bottoming

Product Description

The OSG 2940201 is a spiral flute tap designed for cutting right-hand internal threads to a 1/4-20 UNC specification. Ground from 3% vanadium high-speed steel (HSS) and finished with a steam oxide coating, this tap is built for service in ferrous and hardened materials where conventional straight-flute taps struggle. The 45-degree helix angle drives chips up and out of the hole during cutting, reducing the risk of chip packing in blind-hole applications. With a modified bottoming chamfer and an H7 thread limit, this tap threads close to the bottom of a blind bore while maintaining tight dimensional control. Overall length is 2.5 inches, and it is classified as an oversize tap.

This tap is suited for production and maintenance machining in blind-hole threading operations on alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel. It is used in CNC machining centers, drill presses, and manual tapping setups where a spiral flute geometry is required to evacuate chips away from the cutting zone. The Series 290 designation places it in OSG's standard spiral flute tap line. Licensed machinists, tool-and-die makers, and maintenance technicians in manufacturing environments are the primary installers and users.

Key Features

• 45-degree helix angle promotes upward chip evacuation in blind-hole tapping
• Modified bottoming chamfer threads to near the bottom of a blind bore
• 3% vanadium HSS construction for improved wear resistance over standard M2 HSS
• Steam oxide coating reduces friction and provides light corrosion protection
• H7 thread limit for controlled oversize fit in tight-tolerance applications
• Right-hand flute direction and right-hand thread on a 3-flute design

Compatibility

Designed for 1/4-20 UNC blind-hole threading in alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel. Compatible with standard 1/4-20 tap holders and tapping chucks sized for a 0.255-inch shank diameter.

Installation Notes

This tap is installed by qualified machinists or maintenance technicians using a tap wrench, tapping head, or CNC rigid-tapping setup. Ensure the drill hole is sized to the correct tap drill diameter for 1/4-20 UNC prior to tapping. Use appropriate cutting fluid for the workpiece material, especially when tapping stainless or hardened steel. Do not exceed the recommended cutting speed for the material grade, and back out periodically in manual applications to clear chips and prevent tap breakage.