Fig. 1558 represents a planer by David W. Pond, of Worcester, Massachusetts, in which the rod x is connected direct from s to a pivoted piece y in which is a cam-shaped slot through which pass pins from the belt-moving arms u and w. The shape of the slot in y is such as to move the belt-moving arms one in advance of the other, as described with reference to Fig. 1566.
The feed motions are here operated by a disk c, which is actuated one-half a revolution when the work table is reversed. This disk is provided on its face with a slide-way in which is a sliding block that may be moved to or from the centre of c by the screw shown, thus varying at will the amount of stroke imparted to the rod which moves the rack by means of which the feed is actuated through the medium of the gear-wheels at f. The handle g is for operating the feed screw when the self-acting feed is thrown out of operation, which is done by means of a catch corresponding in its action to the catch shown in Fig. 1501. s and s′ are in one piece, s′ being to move the two driving belts on to the loose pulleys so as to stop the work table from traversing.
The size of a planer is designated from the size of work it will plane, and this is determined by the greatest height the tool can be raised above the planer table, the width between the stanchions, and the length of table motion that can be utilized while the tool is cutting; which length is less than the full length of table stroke, because in the first place it is undesirable that the rack should pass so far over the driving wheel or pinion that any of the teeth disengage, and, furthermore, a certain amount of table motion is necessary to reverse after the work has passed the tool at the end of each stroke.
Fig. 1559 represents a method employed in some English planing machines to drive the work table and to give it a quick return motion. In this design but one belt is used, being shifted from pulley a, which operates the table for the cutting stroke, to pulley j, which actuates the table for the return stroke. The middle pulley k is loose upon shaft b, as is also pulley j, which is in one piece with pinion j′. Motion from a is conveyed through shaft b and through gear c, d, e to f, and is reduced by reason of the difference in diameter between d and e and between f and g. Motion for the quick return passes from j direct to f without being reduced by gears d, e, hence the difference between the cutting speed and the speed of the return stroke is proportionate to the relative diameters or numbers of teeth in d and e, and as e contains 12 and d 20 teeth, it follows that the return is 8⁄12 quicker than the cutting stroke.
In this design the belt is for each reversal of table motion moved across the loose pulley k from one driving pulley to the other, and therefore across two pulleys instead of across the width of one pulley only as in American machines.
In American practice the rack r, Fig. 1559, is driven by a large gear instead of by a pinion, so that the strain on the last driving shaft s, in Fig. 1560, shall be less, and also the wheel less liable to vibration than a pinion would be, because in the one case, as in Fig. 1559, the power is transmitted through the shaft, while in the other, as in Fig. 1560, it is transmitted through the wheel from the pinion p to the rack r.
| VOL. I. | EXAMPLES OF PLANING MACHINES. | PLATE XVII. | |
| Fig. 1561 | |||
| Fig. 1561. | |||
| Fig. 1563 | |||
| Fig. 1563. | |||
Fig. 1561 represents a planer, designed for use in situations where a solid foundation cannot be obtained, hence the bed is made of unusual depth to give sufficient strength and make it firm and solid on unstable foundations, such as the floors in the upper stories of buildings. In all other respects the machine answers to the general features of improved planing machines.
As the sizes of planing machines increase, they are given increased tool-carrying heads; thus, Fig. 1562 represents a class in which two sliding heads are used, so that two cutting tools may operate simultaneously. Each head, however, is capable of independent operation; hence, one tool may be actuated automatically along the cross slide to plane the surfaces of the work, while the other may be used to carry a cut down the sides of the work, or one tool may take the roughing and the other follow with the finishing cut, thus doubling the capacity of the machine.
In other large planers the uprights are provided with separate heads as shown in the planer in Fig. 1563, in which each upright is provided with a head shown below the cross slide. Either or both these heads may be employed to operate upon the vertical side faces of work, while the upper surface of the work is being planed.
The automatic feed motion for these side heads is obtained in the Sellers machine from a rod actuated from the disk or plate in figure, this rod passing through the bed and operating each feed by a pawl and feed wheel, the latter being clearly seen in the figure.
To enable the amount of feed to be varied the feed rod is driven by a stud capable of adjustment in a slot in the disk.
Fig. 1563 represents a planing machine designed by Francis Berry & Sons, of Lowerby Bridge, England. The bed of the machine is, it will be seen, L-shaped, the extension being to provide a slide to carry the right-hand standard, and permit of its adjustment at distances varying from the left-hand standard to suit the width of the work. This obviously increases the capacity of the machine, and is a desirable feature in the large planers used upon the large parts of marine engines.
Rotary Planing Machine.—Fig. 1564 is a rotary planing machine. The tools are here carried on a revolving disk or cutter head, whose spindle bearing is in an upper slide with 2 inches of motion to move the bearing endways, and thereby adjust the depth of cut by means of a screw. The carriage on which the spindle bearing is mounted is traversed back and forth (by a worm and worm-wheel at the back of the machine) along a horizontal slide, which, having a circular base, may be set either parallel to the fixed work table or at any required angle thereto.
By traversing the cutter head instead of the work, less floor space is occupied, because the head requires to travel the length of the work only, whereas when the work moves to the cut it is all on one side of the cutter at the beginning of the cut, and all on the other at the end, hence the amount of floor space required is equal to twice the length of the work.
The disk or cutter head is in one piece with the spindle, and carries twenty-four cutters arranged in a circle of 36 inches in diameter. These cutters are made from the square bar, and each cutting point should have the same form and position as referred to one face, side, or square of the bar, so that each cutter may take its proper share of the cutting duty; and it is obvious that all the cutting edges must project an equal distance from the face of the disk, in which case smooth work will be produced with a feed suitable for the whole twenty-four cutters, whereas if a tool cuts deeper than the others it will leave a groove at each passage across the work, unless the feed were sufficiently fine for that one tool, in which case the advantage of the number of tools is lost.
The cutters may be ground while in their places in the head by a suitable emery-wheel attachment, or if ground separately they must be very carefully set by a gauge applied to the face of the disk.
Fig. 1565 represents a planer by William Sellers and Co., of Philadelphia, Pennsylvania. This planer is provided with an automatic feed to the sliding head, both horizontally and vertically, and with mechanism which lifts the apron, and therefore the cutting tool, during the backward stroke of the work table, and thus prevents the abrasion of the tool edge that occurs when the tool is allowed to drag during the return stroke. The machine is also provided with a quick return motion, and in the larger sizes with other conveniences to be described hereafter.
The platen or table is driven by a worm set at such an angle to the table rack as to enable the teeth of the rack to stand at a right angle to the table length, and as a result the line of thrust between the worm and the rack is parallel to the V-guideways, which prevents wear between the Vs of the table and of the bed.
The driving pulleys are set at a right angle to the length of the machine, their planes of revolution being, therefore, parallel to the plane of revolution of the line or driving shaft overhead, and parallel with the lathes and other machines driven from the same line of shafting, thus taking up less floor space, while the passage ways between the different lines of machines is less obstructed.
By setting the worm driving shaft at an angle the teeth of the worm rotate in a plane at a right angle to the length of the work-table rack, and as a result the teeth of the worm have contact across the full width of the rack teeth instead of in the middle only, as is the case when the axis of a worm is at a right angle to the axis of the wheel or rack that it drives.
Furthermore, by inclining the worm shaft at an angle the teeth of the rack may be straight (and not curved to suit the curvature of the worm after the manner of worm-wheels), because the contact between the worm and rack teeth begins at one side of the rack and passes by a rolling motion to the other, after the manner and possessing the advantages of Hook’s gearing as described in the remarks made with reference to gear-wheel teeth.
By inclining the worm shaft, however, the side thrust incidental to Hook’s gearing is avoided, the pressure of contact of tooth upon tooth being in the same direction and in line with the rack motion. As the contact between the worm teeth and the rack is uniform in amount and is also continuous, a very smooth and uniform motion is imparted to the work table, and the vibration usually accompanying the action of spur-gearing is avoided.
The worm has four separate spirals or teeth, hence the table rack is moved four teeth at each worm revolution, and a quick belt motion is obtained by the employment of pulleys of large diameter.
It is desirable that the belt motion of a planing machine be as quick as the conditions will permit, because the amount of power necessary to drive the machine can thus be obtained by a narrower belt, it being obvious that since the driving power of the belt is the product of its tension and velocity the greater the velocity the less the amount of tension may be to transmit a given amount of power.
The mechanism for shifting the belt to reverse the direction of table motion is shown in Fig. 1566 removed from all the other mechanism.
To the bracket or arm b are pivoted the arms or belt guides c and d and the piece g. In the position occupied by the parts in the figure the belt for the forward or cutting stroke would be upon the loose pulley p′, and that for the quick return stroke would be upon the loose pulley p, hence the machine table would remain at rest. But suppose the rod f be moved by hand in the direction of arrow f, then g would be moved upon its pivot x, and its lug h would meet the jaw i of c, moving c in the direction of arrow a, and therefore carrying the belt from loose pulley p′ on to the driving pulley p′′, which would start the machine work table, causing it to move in the direction of arrow w until such time as the stop a meets the lug r, operating lever e and moving rod f in the direction of arrow d. This would move g, causing its lug h to meet the jaw j, which would move c from p′′ back to the position it occupies in the figure, and as the motion of g continued its shoulder at g′ would meet the shoulder or lug t of k (the latter being connected to d) and move arm d in the direction of b, and therefore carrying the crossed belt upon p, and causing the machine table to run backward, which it would do at a greater speed than during the cutting traverse, because of the overhead pulley on the countershaft being of greater diameter than that for the cutting stroke.
It is obvious that since each belt passes from its loose pulley to the fast one, the width of the overhead or countershaft pulleys must be twice as wide as the belt, and also that to reverse the direction of pulley revolution one driving belt must be crossed; and as on the countershaft the smallest pulley is that for driving the cutting stroke, its belt is made the crossed one, so as to cause it to envelop as much of the pulley circumference as possible, and thereby increase its driving power. The arrangement of the countershaft pulleys and belts is shown in Fig. 1567, in which s is the countershaft and n, o the fast and loose pulleys for the belt from the line shaft pulley; q′ is the pulley for operating the table on the cutting stroke (with the crossed belt), while q is the pulley for operating the table on its return stroke. The difference in the speed of the table during the two strokes is obviously in the same proportions as the diameters of pulleys q′ and q.
The feed rod, and feed screw, and rope for lifting the tool on the back stroke are operated as follows:—
Fig. 1568 is an end view of the mechanism viewed from the front of the machine, and Fig. 1569 is a side view of the same.
The shaft of the driving pulleys (p p′ and p′′, Fig. 1567) drives a pinion operating the gear wheel w, upon the face of which is a serrated internal wheel answering to a ratchet wheel, and with which a pawl engages each time the direction of pulley revolution (or, which is the same thing, the direction of motion w) reverses, and causes the pawl and the shaft, to which the plate p, Fig. 1569, is fast, to make one-half a revolution, when the pawl disengages and all parts save the wheel w come to rest.
From this plate p the feed motions are actuated, and the tool is lifted during the back traverse of the work table by the following mechanisms.
Referring to Fig. 1570, upon the plate p is pivoted a lever q, carrying a universal joint at z, and a nut pivoted at v, and it is obvious that at each half-revolution of p, the rod r is moved vertically. This rod connects to a universal joint j (shown in Fig. 1571) that is pivoted in a toothed segment (k, in the same figure) which engages with a pinion on the feed screw, this pinion being provided with a ratchet and feed pawl (of the usual construction) for reversing the direction of the feed or throwing it out of action.
The amount of feed is regulated as follows:—
Referring to Figs. 1569 and 1570, the amount of vertical motion of rod r is obviously determined by the distance of the universal joint z from the centre of the plate p, and this is set by operating the hand wheel t, which revolves the screw y in the nut v.
For lifting the tool during the return motion of the work and work table, there is provided in the plate p, Fig. 1570, a pin which actuates the rod b, which in turn actuates the grooved segment c.
From this segment a cord is stretched passing over the grooved pulley d, Fig. 1571, thence over pulley e, and after taking a turn around the pulley f, Fig. 1571, it passes to the other end of the cross slide, where it is secured.
This pulley f is therefore revolved at each motion of the plate p, Figs. 1569 or 1570, or in other words each time the work table reverses its motion.
In reference to Figs. 1571 and 1572, f, Fig. 1571, is fast upon a pin g, at whose other end is a pinion operating a gear-wheel h. Upon the face of this gear-wheel is secured a steel plate shown at m in Fig. 1572, which is a vertical section of the sliding head. In a cam groove in m, projects a pin that is secured to the sleeve n, which envelops the vertical feed screw o. This sleeve n has frictional contact at p with the bar q, whose lower end receives the bell crank r, which on each return stroke is depressed, and thus moves the tool apron s, and with it the tool, which is therefore relieved from contact with the cut upon the work.
The self-acting vertical feed is actuated as follows:—
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.
The form of cross bar usually employed in the United States is represented in Fig. 1573, and it is clear that the pressure of the cut is in the direction of the arrow c, and that the fulcrum off which the strain will act on the cross bar is at its lowest point d, tending to pull the top of the saddle or slider in the direction of arrow e, which is directly resisted by the vertical face of the gib, while the horizontal face f of the gib directly resists the tendency of the saddle to fall vertically, and, therefore, the amount of looseness that may occur by reason of the wear cannot exceed the amount of metal lost by the wear, which may be taken up as far as possible by means of the screws a and b, which thread through the saddle and abut against the gib. The gib is adjusted by these screws to fit to the least worn and therefore, the tightest part of the cross bar slideway, and the saddle is more loosely held at other parts of the cross bar in proportion as its slideway is worn.
In this construction the faces of the saddle are brought to bear over the whole area of the slideways surface of the cross bar, because the bevel at g brings the two faces at m into contact, and the set-screw b brings the faces in together. Instead of the screws a and b having slotted heads for a screw driver, however, it is preferable to provide square-headed screws, having check nuts, as in Fig. 1574, so that after the adjustment is made the parts may be firmly locked by the check nuts, and there will be no danger of the adjustment altering.
The wear between the slider and the raised slideways s is taken up by gibs and screws corresponding to those at a and c in the Fig. 1575, and concerning these gibs and screws J. Richards has pointed out that two methods may be employed in their construction, these two methods being illustrated in Figs. 1575 and 1576, which are taken from “Engineering.”
In Fig. 1575 the end s of the adjustment screw a is plain, and is let into the gib c abutting against a flat seat, and as a result while the screw pressure forces the gib c against the bevelled edge of the slideway it does not act to draw the surfaces together at m m as it should do. This may be remedied by making the point of the screw of such a cone that it will bed fair against gib c, without passing into a recess, the construction being as in Fig. 1576, in which case the screw point forces the gib flat against the bevelled face and there is no tendency for the gib to pass down into the corner e, Fig. 1575, while the pressure on the screw point acts to force the slide a down upon the slideway, thus giving contact at m m.
The bearing area of such screw points is, however, so small that the pressure due to the tool cut is liable to cause the screw to indent the gib and thus destroy the adjustment, and on this account a wedge such as shown in Fig. 1577 is preferable, being operated endwise to take up the wear by means of a screw passing through a lug at the outer or exposed end of the wedge.
The corners at i, Figs. 1575 and 1576, are sometimes planed out to the dotted lines, but this does not increase the bearing area between the gib c and the slide, while it obviously weakens the slider and renders it more liable to spring under heavy tool cuts.
Fig. 1578 represents a form of cross bar and gib found in many English and in some American planing machines. In this case the strain due to the cut is resisted directly by the vertical face of the top slide of the cross bar, the gib being a triangular piece set up by the screws at a, and the wear is diminished because of the increased wearing surface of the gib due to its lower face being diagonal.
On the other hand, however, this diagonal surface does not directly resist the falling of the saddle from wear, and furthermore in taking up the wear the vertical face of the saddle is relieved from contact with the vertical face of the cross bar, because the screws a when set up move the top of the saddle away from the cross bar, whereas in Fig. 1573, setting up screw b brings the saddle back upon the vertical face of the cross bar slideway.
Fig. 1579 is a front view, and Fig. 1580 a sectional top view, of a sunk vertical slide, corresponding to that shown in Figs. 1573 and 1578, but in this case the gib has a tongue t, closely fitted into a recess or channel in the vertical slider s, and to allow room for adjustment, the channel is made somewhat deeper than the tongue requires when newly fitted. The adjustment is effected by means of two sets of screws, a and b, of which the former, being tapped into the gib, serve to tighten, and the latter, being tapped into the slide, serve to loosen the gib. By thus acting in opposite directions the screws serve to check each other, holding the gib rigidly in place. To insure a close contact of the gib against the vertical surface of the slide, the screws b are placed in a line slightly outside of the line of the screws a.
Fig. 1581 represents a similar construction when the slideways on the swing frame project outwards, instead of being sunk within that frame.
Fig. 1582 represents the construction of the Pratt & Whitney Company’s planer head, in which the swivel head instead of pivoting upon a central pin and being locked in position by bolts, whose nuts project outside and on the front face of the swing frame, is constructed as follows:—
A circular dovetail recess in the saddle receives a corresponding dovetail projection on the swivel head or swing frame, and the two are secured together at that point by a set-screw a. In addition to this the upper edge b of the saddle is an arc of a circle of which the centre is the centre of the dovetail groove, and a clamp is employed to fasten the swivel head to the saddle, being held to that head by a bolt, and therefore swinging with it. Thus the swivel head is secured to its saddle at its upper edge, as well as at its centre, which affords a better support.
The tool box is pivoted upon the vertical slider, and is secured in its adjusted position by the bolts n in Fig. 1573, the object of swinging it being to enable the tool to be lifted on the back stroke and clear the cut, when cutting vertical faces, as was explained with reference to shaping machines.
The tool apron is in American practice pivoted between two jaws, which prevent its motion sideways, and to prevent any play or lost motion that might arise from the wear of the taper pivoting pin b, in Fig. 1583, the apron beds upon a bevel as at a, so that in falling to its seat it will be pulled down, taking up any lost motion upon b.
The bevel at a would also prevent any side motion to the apron should wear occur between it and the jaws. In addition to this bevel, however, there may be employed two vertical bevels c in the top view in Fig. 1584. In English practice, and especially upon large planing machines, the apron is sometimes made to embrace or fit the outsides of the tool box, as in Fig. 1585, the object being to spread the bearings as wide apart as possible, and thus diminish the effect of any lost motion or wear of the pivoting pin, and to enable the tool post or holder to be set to the extreme edge of the tool box as shown in the figure.
It is desirable that the tool apron bed as firmly as possible back against its seat in the tool box, and this end is much more effectively secured when it is pivoted as far back as possible, as in Fig. 1585, because in that case nearly all the weight of the apron, as well as that of the tool and its clamp, acts to seat the apron, whereas when the pivot is more in front, as m, in Fig. 1573, it is the weight of the tool post and tool only that acts to keep the apron seated.
In small planing machines it is a great advantage to provide an extra apron carrying two tool posts, as in Fig. 1586, so that in planing a number of pieces, that are to be of the same dimension, one tool may be used for roughing and one for finishing the work. The tools should be wider apart than the width of the work, so that the finishing tool will not come into operation until after the roughing tool has carried its cut across.
When the roughing tool has become dulled it should, after being ground up, be set to the last roughing cut taken, so that it will leave the same amount of finishing cut as before.
The advantage of this system is that the finishing tool will last to finish a great many pieces without being disturbed, and as a result the trouble of setting its cut for each piece is avoided; on which account all the pieces are sure to be cut to the same dimension without any further measuring than is necessary for the first piece, whereas if one tool only is used it rapidly dulls from the roughing cut, and will not cut sufficiently smooth for the finishing one, and must therefore be more frequently ground up to resharpen it, while it must be accurately set for each finishing cut. A double tool apron of this kind is especially serviceable upon such work as planing large nuts, for it will save half the time and give more accurate work.
In some planing machines, and notably those made by Sir Joseph Whitworth, a swiveling tool holder is made so that at each end of the stroke the cutting tool makes half a revolution, and may therefore be used to cut during both strokes of the planer table. A device answering this purpose is shown in Fig. 1587. The tool-holding box is pivoted upon a pin a, and has attached to it a segment of a circular rack or worm-wheel, operated by a worm upon a shaft having at its upper end the pulley shown, so that by operating this pulley, part of a revolution at the end of each work-table stroke, one or the other of the two tools shown in the tool box, is brought into position to carry the cut along. Thus two tools are placed back to back, and it is obvious that when the tool box is moved to the right, the front tool is brought into position, while when it is moved to the left, the back or right-hand tool is brought into position to cut, the other tool being raised clear of the work.
The objections to either revolving one tool or using two tools so as to cut on both strokes are twofold: first, the tools are difficult to set correctly; and, secondly, the device cannot be used upon vertical faces or those at an angle, or in other words, can only be used upon surfaces that are nearly parallel to the surface of the work table.
Figs. 1588 and 1589 represent the sliding head of the large planer at the Washington Navy Yard, the sectional view, Fig. 1589, being taken on the line x x in Fig. 1588. c is the cross bar and s the saddle, f being the swing frame or fiddle, as some term it, and s′ the vertical slider; b is the tool box, and a the apron.
The wear of the cross slider is taken up by the set screws a, and that of the vertical slide by the screws b.