<P> Materials that can be milled range from aluminum to stainless steel and almost everything in between . Each material requires a different speed on the milling tool and varies in the amount of material that can be removed in one pass of the tool . Harder materials are usually milled at slower speeds with small amounts of material removed . Softer materials vary, but usually are milled with a high bit speed . </P> <P> The use of a milling machine adds costs that are factored into the manufacturing process . Each time the machine is used coolant is also used, which must be periodically added in order to prevent breaking bits . A milling bit must also be changed as needed in order to prevent damage to the material . Time is the biggest factor for costs . Complex parts can require hours to complete, while very simple parts take only minutes . This in turn varies the production time as well, as each part will require different amounts of time . </P> <P> Safety is key with these machines . The bits are traveling at high speeds and removing pieces of usually scalding hot metal . The advantage of having a CNC milling machine is that it protects the machine operator . </P> <P> Turning is a metal cutting process for producing a cylindrical surface with a single point tool . The workpiece is rotated on a spindle and the cutting tool is fed into it radially, axially or both . Producing surfaces perpendicular to the workpiece axis is called facing . Producing surfaces using both radial and axial feeds is called profiling . </P>

A person who joins metal to metal by heating