Various aspects go into the carving out the threads. The UN thread taps come with various adjustable features. You need coarse taps for carving UNC threads whereas fine finishing is required for the UNF and the UNEF threads. We shall look at the role of chamfers for thread cutting taps.
Let us understand what a chamfer is before going into the details of the arrangement.
In very simple words, the tap chamfer is the tapering of the threads so as to distribute the cutting action equally over several sets of teeth. The type of hole has a lot to do with the style of chamfer you use. There are holes that run very deep and literally go all the way through. You have holes that are shallow though having a larger diameter. Some holes go deep but not all the way. Each type of hole requires different types of thread taps to cut through them. There are three types of holes and hence you have three types of chamfers.
Taper taps: The taper taps have the longest chamfer of the three with an 8 to 10-thread chamfer. This enables the tap to distribute the action over as many teeth as possible. The tapering nature of the tap ensures to act as a guide for the cutting action. You use these taps in holes that run through and in materials that require a tapered guide.
Plug Taps: This is also known as the seconding tap. They use these types of taps in through holes as well in those that have considerable space at the bottom, especially in the blind holes. These taps have a 4 to 6-thread chamfer.
Bottoming taps: Also known as the finishing taps, this 1 to 2-thread chamfer is perfectly designed to thread blind holes.
There are different kinds of thread taps to cater to various types of thread. The UN thread tap and the metric tap are the most popular of taps in the industry. The ACME thread taps and the trapezoidal thread taps are also important because of the sheer enormity of the job.
There was a time when the taps were used manually. That was a tough task as you used to push the tap slowly enough to cut the threads. You had to lubricate the holes continuously as well as remove the chips repeatedly. Today, you have machines doing the work at tremendous speeds. You can drill holes and carve out threads at the same time. The removal of chips is also easy and so is the lubrication. Machines have made it easy for man in many easy.
The UNC threads require coarse threads. Hence, such threads do not require the finishing job. However, in the case of UNF and UNEF threads, you need to do perfect finishing as these are fine threads. You cannot afford to do a coarse job as long as these threads are concerned.
We have seen a lot about thread taps and gauges. All these taps and gauges are available at GaugesTools.