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A magnetic chuck is a device, or work support, that uses magnetic force to hold a ferrous metal item during machining. Also refers to magnets used to hold a work support, such as a vise or other fixture, to the work machine. An electromagnetic chuck is a type of magnetic chuck that produces an adjustable magnetic pull, allowing it to hold a variety of workpieces. Processes using magnetic chucks can include drilling, grinding, and turning. They are not just limited to industrial use; some hobbyists use magnetic chucks.
There are three basic types of magnetic chucks. The permanent magnet chuck has a series of magnetic inserts that are constantly polarized, meaning they have permanent poles and constantly pull on the part. Another type is the electromagnetic chuck, which is activated only while the electrical current is on. This chuck has the advantage of being able to deactivate the magnetic pull, releasing the workpiece quickly and easily. The downside of this chuck is that it releases the workpiece when power is interrupted, often putting the worker at risk of injury if this happens during a work process.
The third type is the electro-permanent magnetic chuck, which is a hybrid of the permanent and electromagnetic chucks. This device locks the piece with an electrical shock and then uses another electrical shock to unlock it. If there is a power outage while a part is running, the chuck will still hold tight. Each magnet has an electrical coil around it that can reverse the polarity of the magnet extremely quickly. Another function of the coil is to control the amount of magnetic attraction exerted by the magnetic chuck.
Magnetic chucks only accept ferrous, iron-based materials, which limits the type of part a machinist can work with. A rare earth metal called neodymium iron boron, or neodymium, creates magnets that are at least five times more powerful than traditional magnets. Manufacturers often use it in industrial magnet applications. Machinists often prefer to work with annealed metal parts because hardened materials sometimes retain magnetism when the chuck or work support is off.
Advantages of using a magnetic chuck generally include reduced machine setup time, reduced setup processes, and reduced chuck damage to work pieces. Sometimes the magnetic force provides a stronger grip on the workpiece. Some magnetic chucks are strong enough to have a holding force of 12 tons per square foot (10886 kg per 0.093 m 2 ), making them useful for removing heavy material.