[Fig. 1656] represents a planer tool holder (by Messrs. Smith & Coventry), in which what is, in effect, a swivel tool post is attached to the end of the holder, thus enabling the tool to be used on either the right or left-hand of the holder at will. The shape of the tool steel is shown in section on the right-hand of the engraving, being narrow at the bottom, which enables the tool to be very firmly held and reduces the area to be ground in sharpening the tool. A side and end view of the holder is shown in [Fig. 1657], in which it is seen that the tool may be given top rake or angle to render it suitable for wrought iron or steel or may be set level for brass work.
Fig. 1658.
In [Fig. 1658] the tool and holder are shown in position on the planer head, the front rake on the tool being that suitable for wrought iron.
It is to be noted, however, that the amount of front rake should, to obtain the best results, be less for steel than for wrought iron, and less for cast iron than for wrought, while for brass there should be none; hence the tool post should be made to accomplish these different degrees of rake in order to capacitate such holders for the four above-named metals. It is an advantage, however, that by inclining the tool to give the top rake, this rake may be kept constant by grinding the end only of the tool to sharpen it, and as the end may be ground to a gauge it is very easy to maintain a constant shape of tool. Furthermore as the tool is held by one binding screw only, it may be more readily adjusted in position for the work than is the case when the two apron clamp nuts require to be operated.
Fig. 1659.