Important Caracteristics of Internal Cutting Taps
To cut internal threads, you must choose the right tap. In this article, you will learn about the characteristics of internal taps and how they affect the selection. We will learn about the following six characteristics: thread type, head shape, cutting point, thread profile, cutting edge, and shank.
Metric taps are basically divided into hand taps and mechanism taps. The advantage of a multi-part hand tap set is that each tap is subjected to less force (less risk of breakage). If you cut crooked with a tapered tap, you can correct it with the next tap.
Machine taps are basically single-cut taps that cut threads in one work process. It simplifies the cutting of straight threads because the bit is aligned vertically with the workpiece in the machine. Which internal tap to use depends largely on factors such as application, time and quantity.
1, Thread type
Threads are standardized and normalized in the ISO standard. These describe, among other things, flank angle, thread diameter, pitch, shank, and tolerance zone.
DIN5157 BSP Hand Tap, G 1/8 G 3/8 G 1/4 2pcs HSS-G
2, Head shape
The head can be pointed or flat. Which one to use depends on whether you are threading a through hole or a blind hole.
However, blind holes have a certain drilling depth at the end in the workpiece and are therefore discontinuous. In this case, it is advantageous that the chips are conveyed upwards out of the hole. This is the case with machine taps with left-handed grooves, which push the chips in the cutting direction.
During the manufacturing process, the tap must be clamped between the shank and the head. This is done at the head end through a centering hole.
3, Point Cutting
Point cuts are located on the head of the tap and are performed on multiple threads.
The threads affect the torque load on the tap and therefore the service life. They also affect the tapping and centering behavior. The more threads on the tap, the less force is applied during the tapping process.
Manual and machine taps for point cutting can have a progressive tap. It is used to break the chips so that they can easily exit the drill hole.
DIN371 DIN376 Machine Tap, Spiral Point through hole M6 M8
4, Thread Profile
The thread profile is defined by the teeth, which cut the thread. This can be clearly seen in the hand crank tap set.
The 3-piece hand taps set consists of a taper, a second and a final tap. Here the thread profile is different; the taper and the second tap do not have a complete profile, only the last tap cuts the entire thread.
Since the force factor does not come into play with machine taps, two additional work steps are saved by using a single-cut tap.
The groove profile is used as an access system for collecting and removing chips. There are two types of grooves: straight grooves and spiral grooves.
Straight grooves are used for through holes, as chips break up and fall into the hole. For blind holes, taps with spiral grooves are advantageous because chips are expelled from the hole against the direction of cutting.
Machine taps with spiral grooves promote chip removal, especially at high speeds.
There are two variants of tool shanks. Overflow shank and reinforced shank. The overflow shank has the same diameter throughout and is always smaller than the core diameter of the thread (through-hole).
In contrast, reinforced shanks increase toward the end. Reinforced shanks are used for hard and difficult to machine workpieces. Because this is usually the case with machine-guided drills, both versions of machine taps are available.
Caution, Since the reinforced shanks of machine taps are coarser than the threads themselves, they cannot be used for machining deep holes.
If you are having trouble finding the right tap, you can of course contact us. The main products of GSRTHREAD are thread cutting tools such as taps and dies, twist drill bits and other drilling tools. The company's pursuit of quality control has led to successful sales and a good reputation in the field of such tools. Please contact us for more info.