Balax 10785-010 Extension Thread Forming Tap 4-40

Product Description

The BALAX 10785-010 is a thread forming extension tap designed for producing internal threads in ductile metals without cutting. Unlike conventional cut taps, thread forming taps displace material rather than remove it, resulting in stronger threads and no chips to clear. This tap is configured in a bottoming chamfer, allowing threading to the bottom of blind holes. Built from high-speed steel with a bright uncoated finish, it is suited for production and maintenance threading operations in metalworking environments. Licensed machinists and toolroom mechanics typically select this tap for close-tolerance work requiring a 2B class of fit.

This extension tap is intended for use where standard-length taps cannot reach, including deep holes, recessed bosses, and confined workpiece geometries. The BXEXT series extension body provides additional reach beyond a standard tap shank. The 4-40 UNC thread size and H5 thread limit make it appropriate for small-diameter precision threading in aluminum, mild steel, and similar ductile materials commonly found in light manufacturing, electronics assembly, and machine shop work.

Key Features

• Thread forming design displaces material for chip-free threading and stronger thread forms
• Bottoming chamfer allows threading to the full depth of blind holes
• H5 thread limit provides controlled tolerance for 2B class of fit applications
• High-speed steel construction offers durability across a range of ductile workpiece materials
• Extension-length body reaches deep or recessed hole locations inaccessible to standard taps
• Right-hand flute direction for standard clockwise threading operations

Compatibility

Designed for 4-40 UNC threaded holes requiring a 2B class of fit in ductile metals. Verify tap holder and drive square compatibility before use; this tap features a 0.1100-inch square drive on a 0.1410-inch shank diameter.

Installation Notes

This tap is installed by qualified machinists using a compatible tap handle or CNC tapping head sized for the shank and square dimensions. Ensure the workpiece is securely fixtured and properly lubricated with an appropriate tapping fluid before threading begins. Power down or disengage the machine spindle before manually handling or changing taps. Do not force the tap if resistance is felt, as thread forming requires sufficient material ductility and correct speed selection to avoid tool breakage.