Tap & Die

Tap: Taps are used to cut the internal screw threads. Taps are made of hardened High CarbonSteel or High Speed Steel. The ends of the shank are square to fit a wrench (figure). Usually tapsare provided in set of three -- taper, second and plug tap.

1. Taper Tap: The tap is tapered off for a length of 8 to 10 threads and is the first tap tobe used in a hole to start the thread form.

2. Second Tap: The tap is tapered off for a length of 4 to 5 threads to facilitate picking upthe threads cut by the taper tap.

3. Plug Tap: This is fully threaded throughout its length and is called a 'bottoming' tap.This tap used to cut the bottom of a blind hole.

Die: Dies are used for cutting external threads on round bar or tubes. Dies are made of Hardened High Carbon Steel or High Speed Steel.

1. Split Die or Button Die: Split die is held in place in the stock as shown in figure 38. The split permits a small amount ofadjustment in the size of the die by adjusting the screws in the stock. Since split dies cut their threadcomplete in one cut, the die thread are tapered and back off for one third of their length.

2. Die nuts: Die nuts are not capable of any adjustment. They are not usuallyemployed for cutting threads from the bar, but for rectifying damage toexisting threads. They are externally formed to hexagonal shape for use witha spanner.