What is machining?
Imagine peeling an apple or when using a plane in carpentary. Skins are removed and chips are developed. Basically machining and/or cutting is an operation where an object is machined into aparticular shape using a sharp edged blade.
When machining takes place the object being machined (the workpiece) and the sharp edge blade (the cutting edge) are subjected to severe impact and rubbing at the point of contact.
To make machining possible, it is essential that the cutting edge is harder than the workpiece material. Generally it is said that a cutting tool needs to be at least 3 times harder than the workpiece material.
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Cutting edge and workpiece
In the animation to the right you can see the relationship of the cutting edge and the workpiece while machining.
At the point of contact, the workpiece and the cutting edge impact with one another and as a result the metal is removed. The metal strips removed are called "chips" or "swarf".
When machining metals, the cutting edge is subjected to severe impact and extremely high temperatures. The faster the work-piece and cutting edge impact and rub with each other, the higher the tempe-rature. Generally, the cutting edge can reach up to temperatures of 800°C.
Cutting tools need to be able to withstand the impact and tempe-ratures encountered when machining without sacrifcing hard-ness. Because of this, materials like "high-speed steels" and "cemented carbides" have been widely used. Nowadays, the "cemented carbides" are the mainstream.