Tap and Die - Die

The die cuts a thread on a preformed cylindrical rod, which creates a male threaded piece which functions like a bolt. The dies shown are

• top left: an older split die, with top adjusting screw
• bottom left: a one piece die with top adjusting screw
• center: a one piece die with side adjusting screw (barely visible on the full image)
• right: two dies with side adjusting screws

A cylindrical blank, which is usually slightly less than the required diameter, is machined with a taper (chamfer) at the threaded end. This chamfer allows the die to ease onto the blank before it cuts a sufficient thread to pull itself along.

The adjusting screws allow the die to be compressed or expanded to accommodate slight variations in size, due to material, manufacture, or die sharpness.

Each tool is used independently, but are usually sold in paired sets of both types, one die and three taps. Some sets may provide a lesser number of taps. The common sets shown are designed for hand operation, but different types such as helical or spiral may be used in production tools such as CNC machining tools, which employ die heads to make large volumes of threaded parts.

Die nuts, also known as rethreading dies, are dies made for cleaning up damaged threads, have no split for resizing and are made from a hexagonal bar so that a wrench or shifter spanner can be used to turn them. Die nuts cannot be used to cut new threads.