Figure 1: A complete tap and die set
A tap and die set is one of those toolboxes that are not immediately intuitive to have but become essential to your work once you have it. It does not matter if you are a mechanic, a craftsman, a metal or woodworker, or even a DIY enthusiast, a tap and die set would be remarkably useful to you. Taps and dies are cutting tools used to create threads on components such as screws, bolts, nuts and to create a threaded hole to screw components into.
A tap is a threaded tool that cuts or forms threads in the female portion of a mating pair. Therefore, a tap will create threads in the inside of a hole. On the other hand, a die is a threaded tool that cuts or forms threads in the male portion of a mating pair. Therefore, a die will create threads on a cylindrical rods surface to create a screw or bolt. Both a tap and a die create new threads or repair damaged threads.
A tap and die set consists of taps, dies, and drill bits of different sizes for various applications. Included in the set are handles for turning. The collection also consists of screw extractors and charts to determine the correct drill and taps to match the thread size and pitch. Some sets may contain twist-lock guides, coarse and fine taps, and other tools at a higher cost.
Taps and dies cut metal and other threads. Produced out of high-speed steel HSS or hardened carbon steel, where the former is much more robust and used for a broader range of materials. These cutting materials are suitable for threading steel, cast steel, cast iron, non-ferrous metals, plastics, softwood, and hardwood.
Taps thread the inside surface of a hole to create components like nuts or holes (blind or through) to screw in a screw or bolt. There are three main types of taps. The plug, second, and taper (also known as bottoming, plug, and taper in the U.S.). The image below illustrates the three types:
Figure 2: The three main types of taps: plug tap (A), second tap (B), and taper tap (C)
As seen in Figure 1, the plug tap is almost without a taper (just one tapered thread) and has a continuous cutting edge. It makes it suitable for cutting threads to the bottom of a blind hole. A plug tap cannot start the tapping process of an unthreaded hole because of the short tapered end. Other tapping types with a tapered end start the tapping process before a plug creates a continuous thread to the bottom.
The second tap has 3 – 5 tapered threads and can therefore start the tapping process. It is the most common type of tap used. The tapered end assists in centering and aligning the tap to the hole.
The taper tap has 8 – 10 tapered threads. Tapping hard materials that require slow tapping or in small applications where the tap can easily break is where the taper tap works best.
Figure 3: Creating a thread by using a tapping tool
Most tapping operations are carried out manually, but power taps are electrically driven, such as the spiral point plug tap. The tapping operation can also be machine driven by a lathe machine, a radial drilling machine, a bench-type drill machine, and similar workshop machines. We will discuss the manual operation of using a tap since it is the most common. The process of tapping involves several steps that are described below:
Figure 4: Taper tap: 6-8-thread chamfer (A), second tap: 4-5-thread chamfer (B), final tap (plug): 2-3-thread chamfer (C)
Figure 4: A solid round die
Dies can thread a cylindrical materials outside surface, such as a rod, to make a bolt or screw. There are two general types of dies: the solid die and the adjustable die. A solid die cuts a nominal thread with a consistent depth. The accuracy is dependent on die precision and wear. The compression and release of the adjustable die is possible to achieve different classes of thread fit. Turning integrated screws adjust the die. Figure 4 shows a typical die design.
The process of threading with a die involves several steps that will be described below:
Figure 4: A solid round die
There are several things to consider when choosing the right tap and die set to use. Here are the important ones: