Osg 1626000408 Thread Forming Sti Tap 4-40 Unc H3

Product Description

The OSG 1626000408 is a thread forming STI tap designed for cutting 4-40 UNC internal threads in a wide range of metallic materials. Unlike cutting taps, thread forming taps displace material rather than remove chips, producing stronger threads with a burnished finish. This tap features a semi-bottoming chamfer, H3 thread limit, and a V finish on high-speed steel construction. It measures 2.4803 inches overall length with a 0.141-inch shank diameter and an 11/16-inch thread length. Installed by machinists and maintenance professionals, it is suited for both production and repair threading applications where thread integrity and dimensional accuracy are critical.

This tap is intended for use in tapping operations on carbon steel, alloy steel, stainless steel, aluminum, nickel, hardened steel, and titanium alloy workpieces. The semi-bottoming chamfer allows threading closer to the bottom of a blind hole compared to a plug chamfer, making it practical for tight-tolerance assemblies. The H3 thread limit and 2B class of fit designation make it appropriate for standard UNC fastener compatibility in both light manufacturing and field repair scenarios.

Key Features

• Thread forming design displaces material rather than cutting chips, producing stronger threads
• Semi-bottoming chamfer for threading closer to the bottom of blind holes
• H3 thread limit with 2B class of fit for standard UNC dimensional compliance
• High-speed steel construction suitable for a broad range of metallic materials including stainless steel and titanium alloy
• V finish on tap body
• Compact square drive size of 0.11 inches for use with standard tap wrenches and holders

Compatibility

Designed for tapping 4-40 UNC threads in carbon steel, alloy steel, stainless steel, aluminum, nickel, hardened steel, and titanium alloy. Compatible with standard tap holders and wrenches sized for a 0.141-inch shank diameter.

Installation Notes

Thread forming taps require a properly sized forming tap drill hole, which differs from standard cut tap drill sizes — consult a thread forming drill chart before drilling. Apply appropriate cutting fluid or tapping compound for the workpiece material to reduce galling, particularly in stainless steel and titanium alloy. Secure the workpiece and ensure the tap is started square to the hole to prevent thread misalignment or tap breakage. Always follow shop safety protocols and use appropriate speed and feed rates for the material being tapped.