Machine Parts

  3-2- 1 Method of Location:  3-2- 1 method of location is the fundamental arrangement of locating system. A work piece may be positively and properly located by means of six pins,so positioned that collectively they restrict the work piece in nine of it’s degree of freedom.For this purpose a definite arrangement is used.This   arrangement is called 3-2-1 method of location.   Cause of using three locating pins in base plane : A minimum of three points or pins or locators are generally used in base plane to locate the work piece, although four or more may be used to provide adequate support. It should be noted that a minimum of three pins will always theoritically establish the same location of the work piece. four or more pins(locators)don’t establish this type of theoritical location because if the work piece surface is not geometrically true, the position is still determined by three pins. Three pining system create one surface which is geometrical

Locating:    The term ‘locating’ refers to the dimensional and positional relationship between the work piece and the cutting tool used on the machine. S imply, locating is the proper positioning of work piece against the cutting tool.  Degrees of freedom of a work piece in space : Any movement of a workpiece in any direction is called degree of freedom. A work piece in space, free to move in any direction is designed around three mutually perpendicular planes.It may rotate in either   of two   opposed directions around each axis, clockwise and anticlockwise.Each direction of movement is considered one degree freedom               Fig:Twelve degree s of freedom  The twelve degree of freedom as they apply to a rectangular prism are shown in fig. shows three views of the prism in orthographic projection, with all twelve degees of freedom indicated in their respective positions.