Fig. 1558Fig. 1558.
Fig. 1558.
Fig. 1558represents a planer by David W. Pond, of Worcester, Massachusetts, in which the rodxis connected direct fromsto a pivoted pieceyin which is a cam-shaped slot through which pass pins from the belt-moving armsuandw. The shape of the slot inyis such as to move the belt-moving arms one in advance of the other, as described with reference toFig. 1566.
The feed motions are here operated by a diskc, 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 ofcby 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 atf. The handlegis 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 inFig. 1501.sands′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. 1559Fig. 1559.
Fig. 1559.
Fig. 1559represents 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 pulleya, which operates the table for the cutting stroke, to pulleyj, which actuates the table for the return stroke. The middle pulleykis loose upon shaftb, as is also pulleyj, which is in one piece with pinionj′. Motion fromais conveyed through shaftband through gearc,d,etof, and is reduced by reason of thedifference in diameter betweendandeand betweenfandg. Motion for the quick return passes fromjdirect tofwithout being reduced by gearsd,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 indande, and asecontains 12 andd20 teeth, it follows that the return is8⁄12quicker than the cutting stroke.
In this design the belt is for each reversal of table motion moved across the loose pulleykfrom one driving pulley to the other, and therefore across two pulleys instead of across the width of one pulley only as in American machines.
Fig. 1560Fig. 1560.
Fig. 1560.
In American practice the rackr,Fig. 1559, is driven by a large gear instead of by a pinion, so that the strain on the last driving shafts, inFig. 1560, shall be less, and also the wheel less liable to vibration than a pinion would be, because in the one case, as inFig. 1559, the power is transmitted through the shaft, while in the other, as inFig. 1560, it is transmitted through the wheel from the pinionpto the rackr.
Fig. 1561represents 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.
Fig. 1562Fig. 1562.
Fig. 1562.
As the sizes of planing machines increase, they are given increased tool-carrying heads; thus,Fig. 1562represents 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 inFig. 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. 1563represents 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 toprovide 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.
Fig. 1564Fig. 1564.
Fig. 1564.
Rotary Planing Machine.—Fig. 1564is 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. 1565represents 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.
Fig. 1565Fig. 1565.
Fig. 1565.
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 theV-guideways, which prevents wear between theVs 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.
Fig. 1566Fig. 1566.
Fig. 1566.
The mechanism for shifting the belt to reverse the direction of table motion is shown inFig. 1566removed from all the other mechanism.
To the bracket or armbare pivoted the arms or belt guidescanddand the pieceg. In the position occupied by the parts in the figure the belt for the forward or cutting stroke would be upon the loose pulleyp′, and that for the quick return stroke would be upon the loose pulleyp, hence the machine table would remain at rest. But suppose the rodfbe moved by hand in the direction of arrowf, thengwould be moved upon its pivotx, and its lughwould meet the jawiofc, movingcin the direction of arrowa, and therefore carrying the belt from loose pulleyp′on to the driving pulleyp′′, which would start the machine work table, causing it to move in the direction of arrowwuntil such time as the stopameets the lugr, operating levereand moving rodfin the direction of arrowd. This would moveg, causing its lughto meet the jawj, which would movecfromp′′back to the position it occupies in the figure, and as the motion ofgcontinued its shoulder atg′would meet the shoulder or lugtofk(the latter being connected tod) and move armdin the direction ofb, and therefore carrying the crossed belt uponp, 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.
Fig. 1567Fig. 1567.
Fig. 1567.
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 inFig. 1567, in whichsis the countershaft andn,othe 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), whileqis 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 pulleysq′andq.
The feed rod, and feed screw, and rope for lifting the tool on the back stroke are operated asfollows:—
Fig. 1568Fig. 1568.
Fig. 1568.
Fig. 1568is an end view of the mechanism viewed from the front of the machine, andFig. 1569is a side view of the same.
Fig. 1569Fig. 1569.
Fig. 1569.
The shaft of the driving pulleys (p p′andp′′,Fig. 1567) drives a pinion operating the gear wheelw, 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 motionw) reverses, and causes the pawl and the shaft, to which the platep,Fig. 1569, is fast, to make one-half a revolution, when the pawl disengages and all parts save the wheelwcome to rest.
From this platepthe feed motions are actuated, and the tool is lifted during the back traverse of the work table by the following mechanisms.
Fig. 1570Fig. 1570.
Fig. 1570.
Largeimage(135 kB).Fig. 1571Fig. 1571.
Largeimage(135 kB).
Fig. 1571.
Referring toFig. 1570, upon the platepis pivoted a leverq, carrying a universal joint atz, and a nut pivoted atv, and it is obvious that at each half-revolution ofp, the rodris moved vertically.This rod connects to a universal jointj(shown inFig. 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 asfollows:—
Referring toFigs. 1569and1570, the amount of vertical motion of rodris obviously determined by the distance of the universal jointzfrom the centre of the platep, and this is set by operating the hand wheelt, which revolves the screwyin the nutv.
For lifting the tool during the return motion of the work and work table, there is provided in the platep,Fig. 1570, a pin which actuates the rodb, which in turn actuates the grooved segmentc.
From this segment a cord is stretched passing over the grooved pulleyd,Fig. 1571, thence over pulleye, and after taking a turn around the pulleyf,Fig. 1571, it passes to the other end of the cross slide, where it is secured.
This pulleyfis therefore revolved at each motion of the platep,Figs. 1569or1570, or in other words each time the work table reverses its motion.
In reference toFigs. 1571and1572,f,Fig. 1571, is fast upon a ping, at whose other end is a pinion operating a gear-wheelh. Upon the face of this gear-wheel is secured a steel plate shown atminFig. 1572, which is a vertical section of the sliding head. In a cam groove inm, projects a pin that is secured to the sleeven, which envelops the vertical feed screwo. This sleevenhas frictional contact atpwith the barq, whose lower end receives the bell crankr, which on each return stroke is depressed, and thus moves the tool aprons, and with it the tool, which is therefore relieved from contact with the cut upon the work.
The self-acting vertical feed is actuated asfollows:—
Largeimage(174 kB).Fig. 1572Fig. 1572.
Largeimage(174 kB).
Fig. 1572.
Referring toFigs. 1571and1572the gear segmentkoperates a pinion upon the squared end of the feed rodl, this pinionlhaving the usual pawl and ratchet for reversing the direction of rod revolution.
The splined feed rodlactuates the bevel pinionm, which is in gear with bevel pinionn, the latter driving pinionp, which is threaded to receive the vertical feed screwo; hence whenpis revolved it moves the feed screwoendways, and this moves the vertical sliderupon which is the apron boxtand the aprons. To prevent the possibility of the friction of the threads causing the feed screwoto revolve with the pinionp, the journaleof the feed screwois made shorter than its bearing inr, so that the nutfmay be used to secure the feed screwoto the slider.
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.
Fig. 1573Fig. 1573.
Fig. 1573.
The form of cross bar usually employed in the United States is represented inFig. 1573, and it is clear that the pressure of the cut is in the direction of the arrowc, and that the fulcrum off which the strain will act on the cross bar is at its lowest pointd, tending to pull the top of the saddle or slider in the direction of arrowe, which is directly resisted by the vertical face of the gib, while the horizontal facefof 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 screwsaandb, 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 tightestpart 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.
Fig. 1574Fig. 1574.
Fig. 1574.
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 atgbrings the two faces atminto contact, and the set-screwbbrings the faces in together. Instead of the screwsaandbhaving slotted heads for a screw driver, however, it is preferable to provide square-headed screws, having check nuts, as inFig. 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.
Fig. 1575Fig. 1575.
Fig. 1575.
Fig. 1576Fig. 1576.
Fig. 1576.
The wear between the slider and the raised slidewayssis taken up by gibs and screws corresponding to those ataandcin theFig. 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 inFigs. 1575and1576, which are taken from “Engineering.”
InFig. 1575the endsof the adjustment screwais plain, and is let into the gibcabutting against a flat seat, and as a result while the screw pressure forces the gibcagainst the bevelled edge of the slideway it does not act to draw the surfaces together atm mas it should do. This may be remedied by making the point of the screw of such a cone that it will bed fair against gibc, without passing into a recess, the construction being as inFig. 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 cornere,Fig. 1575, while the pressure on the screw point acts to force the slideadown upon the slideway, thus giving contact atm m.
Fig. 1577Fig. 1577.
Fig. 1577.
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 inFig. 1577is 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 ati,Figs. 1575and1576, are sometimes planed out to the dotted lines, but this does not increase the bearing area between the gibcand the slide, while it obviously weakens the slider and renders it more liable to spring under heavy tool cuts.
Fig. 1578Fig. 1578.
Fig. 1578.
Fig. 1578represents 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 ata, and the wear is diminished because ofthe 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 screwsawhen set up move the top of the saddle away from the cross bar, whereas inFig. 1573, setting up screwbbrings the saddle back upon the vertical face of the cross bar slideway.
Fig. 1579Fig. 1579.
Fig. 1579.
Fig. 1580Fig. 1580.
Fig. 1580.
Fig. 1579is a front view, andFig. 1580a sectional top view, of a sunk vertical slide, corresponding to that shown inFigs. 1573and1578, but in this case the gib has a tonguet, closely fitted into a recess or channel in the vertical sliders, 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,aandb, 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 screwsbare placed in a line slightly outside of the line of the screwsa.
Fig. 1581Fig. 1581.
Fig. 1581.
Fig. 1581represents a similar construction when the slideways on the swing frame project outwards, instead of being sunk within that frame.
Fig. 1582Fig. 1582.
Fig. 1582.
Fig. 1582represents 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 asfollows:—
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-screwa. In addition to this the upper edgebof 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 boltsninFig. 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.
Fig. 1583Fig. 1583.
Fig. 1583.
The tool apron is in American practice pivoted between two jaws, which prevent its motion sideways, and to prevent any playor lost motion that might arise from the wear of the taper pivoting pinb, inFig. 1583, the apron beds upon a bevel as ata, so that in falling to its seat it will be pulled down, taking up any lost motion uponb.
Fig. 1584Fig. 1584.
Fig. 1584.
Fig. 1585Fig. 1585.
Fig. 1585.
The bevel atawould 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 bevelscin the top view inFig. 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 inFig. 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 inFig. 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, asm, inFig. 1573, it is the weight of the tool post and tool only that acts to keep the apron seated.
Fig. 1586Fig. 1586.
Fig. 1586.
In small planing machines it is a great advantage to provide an extra apron carrying two tool posts, as inFig. 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.
Fig. 1587Fig. 1587.
Fig. 1587.
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 inFig. 1587. The tool-holding box is pivoted upon a pina, and has attached toit 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.
Fig. 1588Fig. 1588.
Fig. 1588.
Fig. 1589Fig. 1589.
Fig. 1589.
Figs. 1588and1589represent the sliding head of the large planer at the Washington Navy Yard, the sectional view,Fig. 1589, being taken on the linex xinFig. 1588.cis the cross bar andsthe saddle,fbeing the swing frame or fiddle, as some term it, ands′the vertical slider;bis the tool box, andathe apron.
The wear of the cross slider is taken up by the set screwsa, and that of the vertical slide by the screwsb.