How are concrete nippers and pliers manufactured?

28th February 2020

How are concretor’s nippers and pliers manufactured?


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		The basic shape of the jaws and handles of concretor’s nippers and pliers is made by a manufacturing process known as drop forging.

		What is forging?
		Forging is a manufacturing process that deforms a metal rod or billet workpiece between two dies (a kind of mould).

		This can be done by either impacting one of the dies or applying a very high pressure to the dies in order to compress the workpiece between them.

		Unlike other manufacturing methods such as casting, during the forging process, as the metal is compressed into the desired shape of the part, the grain structure within the metal is also forced to follow the same shape. This aligning of the grain structure results in a strengthening of the part produced.

		As the workpiece is compressed between the two dies some of the material is pushed out between the two dies. This is called flash. This flash then has to be removed by a subsequent machining process.

		Forging can be performed with either a hot or cold process. However, forging of steel is nearly always performed using the hot process which involves heating the metal rod or billet that is to be forged. By heating the workpiece it not only becomes easier to compress it to the desired shape but also prevents the resulting part from becoming too strong, which would make the subsequent machining difficult.

		Once the machining of the flash has been carried out and the final shape of the part achieved, it can have the cutting edges ground onto the jaws before being heat treated and tempered to give it the required physical properties, such as hardness, for use as concretor’s nippers and pliers.

		How are cutting edges applied?
		Once the basic shape of the handles and jaws have been formed, the cutting edges can be subjected to a further machining process. The process used to apply the cutting edges to the inside of concretor’s nipper and pliers jaws is called grinding.

		What is grinding? Grinding is the process of using a bonded grinding wheel made of abrasive particles to remove material from a workpiece. The grinding wheel is a disc that is spun at high speed, and the workpiece is passed across the side face or circumference surface. Grinding can be done with discs made with grain sizes ranging from 8 (coarse) to 250 (very fine). The finer the grain size, the better the surface finish on the workpiece will be.

		What is heat treating and tempering?
		Heat treating and tempering are manufacturing processes used to alter the physical properties of metal and other materials. Heat treating involves heating the metal up to a very high temperature and then quenching (rapidly cooling) it. This increases the hardness of the metal, but will also make it more brittle.

		Tempering is performed after heat treating, and also involves heating the metal, but to a lower temperature than heat treating, then letting it cool slowly. Tempering will decrease the hardness and brittleness of the metal, and at the same time increase its toughness.

		How are the handles of concretor’s nippers and pliers made?
		The handles of concretor’s nippers and pliers are made using either PVC dipping or injection moulding manufacturing processes.

		What is PVC dipping? PVC (polyvinyl chloride) dip moulding is a manufacturing process that involves a heated former, in the shape of the tool’s handles, being dipped in a bath of liquid PVC. As the former is gradually removed and left to cool, the PVC solidifies on it.

		Once cooled, the PVC is removed from the former by hand and compressed air, before being fitted on the handles of the concretor’s nippers and pliers.

		What is injection moulding? Injection moulding involves raw plastic beads (such as nylon) being fed from a hopper into a heated barrel chamber. This melts the plastic, which is then pushed though the barrel by a screw mechanism and into the cavity within the mould. The molten plastic solidifies within the mould cavity. When the two halves of the mould are separated, the finished part is revealed.

		Injection moulding can be used to make a wide range of products such as plastic toys and mobile phone covers as it’s a very quick and cost-effective way of manufacturing high volume products. It can also make bi-material parts such as the handles found on more ergonomic concretor’s nippers and pliers. A second injection process using TPR (thermoplastic rubber) gives a rubberised grip to the handles for improved comfort and grip.