DIFFERENT TYPES OF METRIC THREAD TAPS

A tap is a tool that almost all engineers involved in the construction business carry around always in their toolbox. It is essential in many different industries as well and is practically used everywhere. While repairing a thread at home, or if you are working in a machine shop, you will be expected to know how to use it. Metric thread taps come in different sizes and shapes and can be used for different purposes.

Taps and Dies

Taps and dies are cutting tools used in threading, to create threads into a hole so that the bolt can be received more effectively. Threading involves making the internal as well as external threads. The internal thread called female thread and the external thread called male thread are joined together to attach pieces of work. A tap is a tool used to form or cut the female threads, for e.g. a nut of a mating pair. A die is a tool used to form or cut the male threads, for e.g. a bolt of the mating pair. It is used to add male threads to bars, studs, or pipes. Tapping is the process of using a metric thread tap to form threads, whereas, forming threads using a die is called threading.

Chasers

Taps and dies can also be used in a process called chasing, which is, to clean up a thread. However, using ordinary taps or dies for cleaning threads will cause some of the material also to be removed, resulting in weaker and looser threads. Hence, dies and taps made especially for this purpose, known as chasers, are typically used for cleaning threads. These chasers are not strong enough to cut new threads, being made of soft material, but they are fluted similar to the regular dies and taps and are tighter fitting. Their main use is to clean the threads of spark plugs used in automobiles, to prevent corrosion and carbon buildup.

How does a tap work?

A hand tap is the simplest cutting tool which works by removing the material from a piece using very sharp teeth. A pilot hole or tap hole is sized according to the material which is to be tapped and the desired thread. The hole has to be lubricated well, so as to prevent breakage and for easier spinning of the tap.

While the tap scrapes down the side of the hole, a spiraling ramp is cut, thus forming the female thread. The tap can either be used to cut a fresh thread or it can be used to repair a damaged threading, by running it into a hole which is already tapped.

Direction of tapping

A tap cuts in a single direction, usually clockwise. When the tap spins, it progressively enters deeper into the hole cutting new threads in the process. The tap is spun for a quarter turn in the clockwise direction and then reversed in the counter-clockwise direction so as to unjam any material trapped inside the tool. This reverse turn helps to back the cut material into the flutes and clears the path for the cutting tool again.