As you can see in the above picture, pincer pliers are made out of two separate pieces which are joined together at the hinge through the riveting process. The two long handles are used to apply force while the sharp edged head is used to perform various functions such as taking out nails from wood, extraction of split pins which are in such a position that they are not easily removable by normal pliers.
The pliers we have studied till now assume that the person using them has got Herculean strength (or is at least strong enough to hold both the handles tightly while applying torque) but there had to be something for ordinary mortals like us as well. Hence the locking pliers were made which can be first loosely fitted on the surface to be gripped and then they can be locked in place only to be opened by loosening that lock. This helps to apply force without having to bother about keeping the handles pressed to apply pressure or grip
As you must have guessed from the name itself, these pliers are not used for any gripping function but purely for cutting purposes. This can cut wires, thin sheets and so forth. As you must have also noticed that the two metal strips protruding out from the plastic covers on the handles. These act as springs to keep the pliers in the open position so that after cutting it is easily returned to the open jaw position.
Hence we saw that there are several types of pliers used in engineering. Let me also remind you that this list is by no means exhaustive, rather it is simply indicative. Yet at the same time we did cover most commonly found pliers and any other pliers are simply minor variations of these types only. For example gas pliers are quite similar to pincer pliers but they have teeth on the inside of their jaws so that objects such as pipes, joints, unions etc can be handled effectively. This concludes our study about pliers and in the next article we will learn about various types of hammers used for mechanical works.