Osg 1400128401 Thread Forming Tap 1/4-28 Unf Cobalt

Product Description

The OSG 1400128401 is a thread forming tap designed for cold-forming internal threads without cutting, producing stronger threads by work-hardening the material rather than removing chips. Built from cobalt high-speed steel with a steam oxide finish, this tap handles 1/4-28 UNF right-hand threads in blind hole applications. The modified bottoming chamfer with 2 to 2.5 chamfered threads allows threading closer to the bottom of a blind hole than a standard plug tap. With an H4 thread limit and an overall length of 2.5 inches, it fits standard tap holders and machines used in precision threading operations. Machinists, tool and die makers, and maintenance technicians install this tap in CNC and manual tapping setups.

This tap is suited for threading blind holes in a range of ferrous and non-ferrous metals commonly encountered in production and repair environments. Rated for alloy steel, carbon steel, stainless steel, die steel, hardened steel, and aluminum, it covers a broad cross-section of workpiece materials found in aerospace, automotive, and general manufacturing. The HY-PRO NRT series is engineered for thread forming rather than thread cutting, meaning it is used exclusively where the base material has enough ductility to flow under the forming lobes. Tapping depth reaches 0.933 inches, making it practical for typical blind hole depths in the 1/4-28 UNF size range.

Key Features

• 1/4-28 UNF right-hand thread form, H4 thread limit for consistent fit
• Modified bottoming chamfer with 2 to 2.5 chamfered threads for threading close to blind hole bottoms
• Cobalt high-speed steel construction for added heat and wear resistance in tough materials
• Steam oxide coating reduces friction and improves lubrication retention during tapping
• No coolant-through design; compatible with standard external flood or manual lubrication
• Thread forming process produces chip-free operation, eliminating chip-packing in blind holes

Compatibility

Designed for blind hole threading in alloy steel, carbon steel, die steel, hardened steel, stainless steel, and aluminum workpieces requiring 1/4-28 UNF internal threads. Material application codes P and N apply per the supplier specification.

Installation Notes

Thread forming taps require a properly sized forming tap drill hole, which is larger than a standard cut tap drill size for the same thread — consult a forming tap drill chart for the correct hole diameter before starting. Always apply a suitable tapping fluid or cutting oil rated for the workpiece material; the steam oxide coating aids lubrication retention but does not replace lubricant. Use a calibrated torque-controlled tapping head or CNC rigid tapping cycle to avoid overloading the tap shank, especially near the bottom of a blind hole. Secure the workpiece fully before tapping and verify spindle alignment to prevent tap breakage.