A Group of CNC Milling Small Fixtures.
A jig is a device for guiding a tool; and a fixture is a device for holding a work- piece securely in a known position. So, for example, you might use a drilling jig that has a bush to guide a drill on to the work (Fig. 4-28). Jigs are not often re- quired on CNC machines, because the machine can position the tool very accu- rately.
More commonly, you might use a fixture to hold a workpiece securely in a known position on the mill table. Typically, the fixture would be a plate with pins to locate the workpiece accurately and clamps to hold the workpiece in position. Once your CNC program has been homed or touched off so that the position of the fixture is recognized by the program, the work can be machined. Putting an- other workpiece in the same fixture allows machining to take place in the same relative position on that workpiece. This means fixtures are very useful for repe- tition machining and are commonly used on a CNC mill.
