When talking about tap and die, I don’t mean tool and die. Taps and die are a tool used to formulate screw threads, which is called threading. A tap is used for cutting the female portion of the mating pair. A die, on the other hand, is used to cut or form the male portion of the mating pair. The process of cutting or forming threads using taps are called tapping. While the process of using a die is called threading.
There is a clear cut difference between Metric Thread sizes and inch thread sizes. The inch sizes are designated using the nominal major diameter and the number of threads per inch.
Metric thread taps call outs are importantly different due to the thread pitch, is designated instead of threads per inch or per mm.
Basically metric call-outs thread ISO the International standard for metrics thread destroys the pitch call outs on hard threads. The method of specialization has major importance that average citizens do not need to memorize pitches just to find a coarse thread.
The total range of metric sizes is available with tape, plug or bottom chamfer. The tapering of the threads at the front end shares the cutting action over different teeth.
The word “hand tap” designated in the 19th century when most internal threading was done by hand. The straight flute design is most often today, though most tapping is presently handled on machines. Hand taps are generally purpose used by hand or on production machines.
A metric thread tap forms a thread on the inside surface of a hole, formulating a female surface which acts like a nut. The three taps in the image demonstrate the primary types mostly used by the most machinist.
The metric thread taps show in the top of the image has a continual cutting edge with almost no taper that is around 1 and 1.5 threads of taper is frequent. This feature allows a bottoming tap to cut threads to the bottom of a blind hole. A bottoming tap us mostly used to cut thread in a hole that has already been kind of threaded using one of the more tapered types of taps. When you look at the tapered end of a bottoming tap is quite short to successfully commence into an unthreaded hole. In the United States, they are mostly recognized as bottoming taps, but in Australia and Britain, they are also recognized as plugs taps.
Metric tap sequence
With soft hardness materials, like plastic, aluminium or mild steel, the easy practice is to use a sequential tap to cut the threads. If the threads are to lengthen to the bottom of a blind hole, the intermediate tap will be therefore used to cut threads till the point of the tap on the will be used to finish the hole. The taper tap will be followed by an intermediate tap and later a bottoming to finish the total operation if threads are to be cut to the bottom of a blind hole,
The taper tap will be followed by an intermediate (plug) tap if threads are to be cut to the bottom of a blind hole, and then a bottoming tap to finish the operation.