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Fig. 1572.

Referring to [Figs. 1571] and [1572] the gear segment k operates a pinion upon the squared end of the feed rod l, this pinion l having the usual pawl and ratchet for reversing the direction of rod revolution.

The splined feed rod l actuates the bevel pinion m, which is in gear with bevel pinion n, the latter driving pinion p, which is threaded to receive the vertical feed screw o; hence when p is revolved it moves the feed screw o endways, and this moves the vertical slide r upon which is the apron box t and the apron s. To prevent the possibility of the friction of the threads causing the feed screw o to revolve with the pinion p, the journal e of the feed screw o is made shorter than its bearing in r, so that the nut f may be used to secure the feed screw o to the slide r.

Planer Sliding Heads.—In order that the best work may be produced, it is essential that the sliding head of a planer or planing machine be constructed as rigid as possible, and it follows that the slides and slideways should be of that form that will suffer the least from wear, resist the tool strain as directly as possible, and at the same time enable the taking up of any wear that may occur from the constant use of the parts.

Between the tool point that receives the cutting strain and the cross bar or cross slide that resists it there are the pivoted joint of the apron, the sliding joint of the vertical feed, and the sliding joint of the saddle upon the cross slide, and it is difficult to maintain a sliding fit without some movements or spring to the parts, especially when, as in the case of a planer head, the pressure on the tool point is at considerable leverage to the sliding surfaces, thus augmenting the strain due to the cut.

The wear on the cross slide is greater at and towards the middle than at the ends, but it is also greater at the end nearest to the operator than at the other end, because work that is narrower than the width of the planing machine table is usually chucked on the side nearest to the operator or near the middle of the table width, because it is easier to chuck it there and more convenient to set the tool and watch the cut, for the reason that the means for stopping and starting the machine, and for pulling the feed motions in and out of operation, are on that side.