The vertical boring mill is seldom equipped with multiple turning tools, but there are cases where production can be increased considerably by their use. One example only is given of the use of an equipment of this kind. Fig. 14 shows a large pulley at A, and this is held by the inside of the larger step in the special jaws B. The buttons G give a three-point support to the work. A special tool-holder D is slotted out to receive the tools E, F and G which are used for the turning and boring. The plate H is fastened over one end of the toolholder in order to tie it together, and the filler-block J gives additional strength while its upper end engages the right-hand ram and acts as a driver. Another block K ties the lower end of the tool-holder together. The left-hand head contains the toolpost L which supports the tool M. This tool is used for facing while the other tools are turning.

Other instances of multiple turning might be given, and illustrations shown, but these would be much on the same order as those which have been mentioned and would be of no particular value as representative types. Tools have been selected for this chapter which seem to best illustrate the principles of design required in the various types.

Fig. 14. Application of Multiple Turning Tool to Vertical Boring Mill.