Arbor-mounted cutters

Cutters which are used close to the spindle, such as shell end mills, are mounted on a stub arbor. Fig. 11.10. This arbor is located, held, and driven in the spindle in the same way as a standard arbor. The cutter is located on a spigot or stub and is held in position by a large flanged screw. Two keys on the arbor provide the drive through key slots in the back face of the cutter. 

Cutters which are mounted directly on the spindle nose are located on a centring arbor, and four tapped holes are provided to hold the cutter in position. The two keys again provide the means of transmitting the drive. 

To prevent deflection of the arbor during heavy cutting operations, it is sometimes necessary to mount a second arbor support nearer the spindle nose. The cutter is then positioned between the two supports. 

Large face mills are mounted directly on the spindle nose. To ensure correct location and concentricity, a centring arbor with the appropriate international taper is held in the spindle by the drawbar. The diameter on the end of the centring arbor locates the cutter, which is driven by the spindle keys through a key slot in the back face of the cutter. The cutter is held in position by four screws direct into the spindle nose. Fig. 11.12. 

There are many different types of milling cutters available, and for convenience they can be classified according to the method of mounting those with a central hole for mounting on an arbor, those with a screwed shank for holding in a special chuck and the large facing cutters which mount directly on to the spindle nose. 

Cutters which are used close to the spindle, such as shell end mills, are mounted on a stub arbor. 

Alternatively, a protractor is used to set the workpiece at 45° Fig. 11.18 stage 10. These two final stages are carried out using a 5 mm side-and-face cutter mounted on a standard arbor. 

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