Fig. 1640.
As horizontal surfaces can be planed very much quicker than vertical ones, it frequently occurs that it will pay to take extra trouble in order to chuck the work so as to plane it horizontally, an excellent example being the planing of the faces of the two halves of a large pulley, the chucking of which is illustrated in [Fig. 1640].
Four pieces, as at a, are made to engage the rims of the two halves of the pulley and hold them true, one with the other. The two plates t′ and t′ are set under the pulley halves to level the upper faces, and wooden clamps c, c, are bolted up to hold the pulleys together at the top, w representing wedges between the hubs. s represents supports to block up the pulley near its upper face, and at p are clamps to hold the two halves to the table. It is found that by this method of chucking more than half the time is saved, and the work is made truer than it is possible to get it by planing each half separately and laying them down on the table.
Fig. 1641.
Supplemental tables may also be made in two parts, the upper one being capable of swiveling as in [Fig. 1641], the swiveling device corresponding to that shown for the Thomas shaper chuck in [Fig. 1530]. This enables the work to be operated upon on several different faces without being released from the chuck. Thus in figure the segment could be planed on one edge and the upper table swiveled to bring the other edge in true with the table, which would be a great advantage, especially if the face it is chucked by has not been trued.