Roll Feed Wood Planing Machine

Fig. 3157 represents a roll feed wood planing machine, designed and constructed by George Richards & Co., of Broadheath, near Manchester, England, the construction being more fully shown in the detailed figures following. The machine consists essentially of a framework, carrying a cutter head with two knives, and having a pair of feed rolls, in front and a pair behind it. The front pair feed the timber to the cutter head and the back pair deliver it from the cutter head.

Each pair of rolls is geared together, so that both the top and bottom rolls act to give a positive feed. Immediately in front of the cutter head and between it and the feed rolls (i. e. the front pair of rolls), is a pressure bar extending across the full width of the machine, and having at its lower extremity a steel spring which presses the work down to the table, and thus causes it to be planed of an equal thickness throughout its length. Immediately behind the cutter head and between it and the delivery rolls (i. e. the back pair of rolls), is a pressure bar that also extends across the machine and prevents the timber from rising up from the table after it has passed the cutters, all timber being found to have a tendency to rise after having been acted upon by the cutters. The arrangement of the feed rolls, delivery rolls and pressure bars is shown in Fig. 3158, in which t, t, t, represents three sections of the work table and w, w, a piece of work passing through the machine in the direction of the arrow. Feed roller f is fluted to increase its grip upon the work and insure a positive feed. The lower feed roller f′, and the lower delivery roller d′, are fixed in position, their upper surface projecting above the work table to about ⁄100 inch. This is necessary to take the thrust of the upper rolls (f, d) and prevent them from forcing the work down upon the surface of the table with an undue amount of pressure, which would induce friction and consume an unnecessary amount of power in driving the rolls. The method of adjusting the lower rolls will be explained presently.

Between the cutter head c and the feed roll f is the pressure bar p, and behind the cutter head is the pressure bar b, both these bars being more clearly seen in Fig. 3159, in which the work w is shown entering the machine, and the lower rolls and work table are removed.

Pressure bar p has at its lower end a steel spring j, Fig. 3159, and is supported at each end by circular links y, projecting into grooves provided in the main frame of the machine, as shown in Figs. 3160 and 3161, in which c is the cutter spindle, y the circular link at the end of pressure bar p, and y the circular link at the end of pressure bar b, the two fitting into the one stepped groove.

This groove is concentric with the cutter spindle c, so that the pressure bars keep at a positive or equal distance from the edges of the cutter, no matter what the thickness of the work or the depth of the cut may be.

In Fig. 3162, the work is shown passing beneath the two upper rollers, and the spring j (which extends the whole length of the pressure bar), is depressed from the weight of the bar. By this construction, the work is pressed to the table at a point as close as possible to the cutters. The pressure bar p cannot drop beyond a certain point, because of its tail piece y′, Fig. 3160, which rests on the top of the frame at y′′ when the bar p has fallen to its required limit.

The feed pressure bar p is bolted to its circular links, as shown in Fig. 3162, in which y is a part of the circular link which is bolted to the pressure bar p.

The delivery pressure bar b (Fig. 3160) is riveted to and forms part of its links y. It acts through the medium of spiral springs s, which are carried in cases or boxes s′, which overhang the end of the bar b. A set screw s′′ regulates the pressure of the spring, and a screw a (Fig. 3162) regulates the height of the pressure bar.

The adjustments of the feed and delivery rollers are made as follows:

The feed pressure is obtained through the medium of weights, shown at w, w′, in Fig. 3163, upon the bars a, a′, whose ends are pivoted to the lower ends of links m, n, the upper ends of which are pivoted to the side frame of the machine.

Bar a engages or rests at e, on a lug or projection on the link i, which fits in a recess provided in the side of the frame. This link i, extends up and has a bearing to receive the feed roller (f, Fig. 3160), whose driving gear is shown at o.

It is obvious therefore, that the amount of pressure on the feed roller f may be varied by moving the weight w along the bar a.

Similarly for the delivery pressure roller, the weight w′ is adjustable along the bar a′, which is pivoted to link n, and rests upon i at e′. The link i′ is guided in ways in the side frame of the machine, and at its upper end carries the delivery roller d, whose driving gear is shown at o′ (Fig. 3163).

It is obvious that there are bars a, a′, and links i, i′, on both sides of the machine, so as to adjust the feed rollers at both ends.

The work table and the two lower rollers are adjusted for different thicknesses of work as follows:

Between the two main side frames m and m′, Fig. 3164, are two frames having corresponding inclines or slideways, of which the upper carries the work table and the lower rolls.

The lower incline sits on ways k, k, Fig. 3164, cast on the side frame, and is capable of being moved endwise by means of the hand wheel r, Figs. 3163 and 3164, which operates a screw threaded into the lower incline. When the lower incline is moved endways, the upper one, which carries the work table, is moved vertically, and as the lower feed rolls are carried by the upper incline, and the upper rolls are guided to move vertically only, the lower rolls maintain their position beneath the upper ones, or in other words, the table and lower rolls move together in a vertical direction only, when the lower incline is operated.

The lower rollers run in bearings formed in the links q, q, Fig. 3160, which are pivoted at their other ends to the upper incline. On the sides of the incline are lugs through which pass adjustment screws z, which by operating beneath the outer ends of the links q, q, adjust the heights, bearings of the lower rollers so that the uppermost point on the circumference stands about ⁄100 inch above the level of the work table surface.

The upper surface of the lower incline is shown by the dotted line f, f, f, in Fig. 3163.

We may now consider the means employed to drive the rolls, first remarking that the upper rolls f and d, are given a motion slightly quicker than the lower ones, so as to cause them to clean themselves (from particles of wood that might otherwise cling to them), by a sort of rubbing action which is due to their velocity being greater than the lower rolls and the work. This rubbing action is due to the fact that the work has the slower motion of the lower rollers, resisting the quicker motion of the upper ones, and as a result there is a certain amount of slip between the upper rollers and the work.

Another and important feature, is that the upper delivery roller (d, Fig. 3160), is placed from ⁄4 to ⁄2 inch nearer to the cutter head than the bottom delivery roll, which assists in keeping the work down upon the table.

The mechanism for driving the feed rolls is shown in Figs. 3163, 3164 and 3165, in which l, l are the pulleys which receive motion from a countershaft, and drive the cutter head, being fast upon its shaft, as is also the pulley s, which connects by belt and drives pulley t, on whose shaft is the stepped pulley u, which connects by a crossed belt to pulley v, which drives the feed gear through the medium of the pinion a. The two steps on pulleys u and v, obviously give two rates of feed.

The pinions o and o′, both receive motion from the gear wheel e, this part of the gearing consisting of gears a, b, c, d and e, and as both pinions receive motion from the same gear, their revolutions are equal. The lower feed roll is driven by the pinion p, which gears with and is driven by wheel d, whose face is broad enough to meet p, which sits nearer to the frame than pinion o does, so that the teeth of p may escape those of o.

Now the velocities of all the wheels o, o′, e, d and p, will be equal at the pitch circles, because they constitute a simple train of gearing. Thus if d moves through a part of a revolution equal to the pitch e, then o and o′ will move through the same distance, because the wheels are in continuous gear. Now as d drives p, therefore the velocity of p must at the pitch circle be the same as d, let the numbers of teeth in the respective wheels be what it may, and it follows that the velocities of o, e, d and p are at the pitch circles equal. But by making the diameter of the upper roll greater than the pitch circle of its gear o, and the diameter of the lower roll correspondingly less than the diameter of the pitch circle of its pinion p, the velocity of the circumference of the upper roll will be greater than that of the lower roll, and the rubbing action before referred to with reference to the upper roll will thus be induced.

Referring now to the lower delivery roll, its pinion x receives motion through gear w, which is also driven by gear e, which has a broad face so as to gear with x, which is behind and below gear o′. In this case the circumstances are the same, as will be seen from the following.

An inch of motion of the pitch circle of e will produce an inch of motion at the pitch circles of o′ and of w and x, hence the velocities of the pitch circles will be equal, and if the diameters of the upper and lower rolls are equal, or the same as the pitch circles, the velocities of the circumferences of the respective rolls will be equal, but by making the diameter of the upper delivery roll greater than that of the pitch circle of its pinion, and that of the lower roll less, a rubbing action is induced between the roll and the work, and this rubbing action will keep the roll clear of any dust, etc., that might otherwise cling to it.

The cutter head is formed triangular, as in Fig. 3166, carrying three knives. The knives are set at an angle to the axis of the cutter bar or cutter head. When the knives are at an angle, they take their cut gradually, and the cutting action is more continuous, which diminishes the vibration of the machine, and causes the finished surface to be smoother. Furthermore, the knives take a shearing cut, and therefore cut more easily and freely.

In some practice the knives are made spiral, but spiral knives are difficult to bed properly to the cutter head, and also difficult to grind. The cutter head is made of a solid mild centre steel forging, and runs in phosphor bronze journals, in which it has about ⁄8 inch end play, which tends to distribute the oil along the bearing. It is driven by a pulley at each end, the pulleys seating on a cone.

The amount of skew is about ⁄4 inch for a cutter head carrying a knife 30 inches long, and about ⁄8 inch for a cutter head whose knives are 10 or 12 inches long.

Figs. 3167 and 3168 represent a machine in which there are three feed rolls and one delivery roll, all being driven.

First there is the pair of feed rolls the bottom roll of which is set sufficiently above the surface of the table to relieve the work of friction upon the table.

The work next meets an upper feed roll that acts to force the work down to the table surface (there being in this case no lower feed roll).

After passing the knives, the work is carried out by a delivery roll that also acts to keep the work down to the table face.

All three upper rolls are provided with rubber springs in the casings h, h′.

p, p, are the pulleys for the cutter head and b, those for the feed works, which have two speeds. The feed is thrown in and out by the lever d, which moves the pinion d endways and engages or disengages it from its gear wheel.

Figs. 3169, 3170, 3171 and 3172 represent a pony planer, by P. Pryibil.

Referring to the sectional view Fig. 3170, the work table slides in vertical slideways s, in the side frames, the elevating screw being operated by the bevel gears at g, which receive motion from the hand wheel m in Figs. 3170 and 3171. There are four upper rolls, marked 1, 2, 3 and 4 respectively, and of these the first two are fluted in the usual way. There are two lower rolls, marked respectively 5 and 6. The fluted feed rolls 1 and 2 are weighted, the weight lever acting on the rod r, which at its upper end connects to the cap y, which covers the bearings of feed rolls 1 and 2. By this construction the two rolls are acted upon by the same weights and levers, the rolls being of course weighted at each end, or in other words on both sides of the machine.

The delivery rolls 3 and 4 receive their pressure by the construction shown in Fig. 3172, the bearings of the rolls being held down by rubber cushions receiving pressure from the cap e, screwed down by the bolt and nut.

The rolls 5 and 6 are idle rolls, and are set to just relieve the work from undue pressure on the work table.

By this construction of feed mechanism the following ends are attained. First, sufficient feed power for heavy cuts is obtained without driving the lower rolls. Second the work is held to the table on both sides of the cutter head, hence there will not be left on the end of the work the step that is left when but two upper and two lower rolls are used, and which occurs because the work falls after leaving the feed rolls, whereas, in this machine the work is held to the table by rolls 2 and 3.

The cutter head h, Fig. 3170, has in front of it the pressure bar p, whose lever is shown at l and the weight at w. On the delivery side of the cutter head is a pressure bar r, which is acted upon by a spiral spring in the box c. In the engraving to the right of Fig. 3170 the knife k is shown in action on a piece of work, and it is seen that the end of the pressure bar p coming close to the edge of the knife prevents the pressure of the cut from splitting or splintering off the end of the work at a, and therefore acts as what is termed a chip break. Furthermore, the sides of the cutter head between the knives being hollowed out gives the shavings s room to curl in and prevent the work from splintering at the end when the cut is terminating.

Balancing Cutter Heads and Knives.—Planer knives must be balanced as accurately as possible, in order that they may run steadily and smoothly, and therefore produce smooth work.

The first requisite for proper balancing is that the cutter head itself be properly balanced, and in order that this may be the case the faces forming the knife seats must be equidistant from the axis of the cutter head, and the journals must run true, being best tested on dead centres. The holes for the cutter bolts should all be drilled to the same depth, and tapped equally deep. The faces or seats for the knives should be parallel one to the other, and this may be tested by a pair of straight edges, one pressed to each face and the width between them measured at each end, or if a long surface plate is at hand, one face of the head may be rested on the surface plate, and the straight edge ruled on the other face, and its distance measured from the surface plate at each end, with a pair of inside callipers delicately adjusted.

A straight edge rested lengthways along the knife seat of the head and projecting over the journal will show whether each knife seat is equidistant from the journal as it should be, the measurement being taken with a pair of inside callipers adjusted to just sensibly touch the journal and the straight edge. This measurement should be taken at each end of the head.

In all tests made with straight edges, the straight edge should be turned end for end and each measurement repeated, because, if the straight edge is true, turning it end for end will make no difference to the measurement, while if the straight edge is not true the measurement will vary when the straight edge is reversed.

If the cutter head is square, the straight edge tests may be applied to all four of its faces, and they may then be tested with a square, and if the head shows no error under these tests, and the bolt holes or slots are of equal diameter and depths, the head will be correct as far as it can be tested without running it.

A cutter head may be roughly tested by placing it between the lathe centres, both centres being oiled and delicately adjusted so as to just prevent end motion of the head without perceptible friction when the head is revolved by hand.

The first thing to test is whether the journals run true, which may be tested by a pointer fastened in the slide seat, and moved up to just touch the journal. The pointer should be soft, and not a cutting tool, unless indeed it be set so high in the slide rest that it cannot cut.

If the journals do not run true, the next thing to test is whether the body of the head runs true to the centres, which may be done by first setting a pointer to just touch the extreme corners of the head at each end and in the middle of its length, and if there is an error in the same direction as the test at the journal shows, then the centres of the head are out of true, and must be corrected before a test of this kind can be proceeded with.

But the body of the head may show true at the corners while the journals do not run true, and if this is the case we may further test the body of the head as follows:

With the lathe slide rest at one end of the head we may set a pointer so that it will just pass on the flat of the cutter seat and make a mark when the slide rest is traversed along the lathe bed. We then move the slide rest so as to bring the pointer to the journal end of the head; give the head a half a revolution on the centres and try the pointer on the flat of the cutter seat, and if it makes a mark of equal strength, then two faces of the head are equidistant from the axis of the head.

The next thing to do is to make the same test at the other end of the head, and in order to do this without moving the pointer, and therefore without altering its adjustment, we must move the slide rest so as to bring the pointer opposite to the lathe centre, and out of the way of the body of the head, and take the cutter head out of the lathe and turn it end for end, and then repeat the test with the pointer, which will show whether both ends of those two flats are alike.

This test we repeat on the other two faces of the head, and if they show true, then the head is true, except the journal, which must be made true with the head.

This testing will clearly show any want of truth in either the head or the journals, and in what direction correction needs to be made.

Now suppose the above tests do not disclose any error, either in the journals or in the head, and we may continue the tests by revolving the head by hand between the dead centres, and apply the pointer to the journals while the head is revolved as quickly as possible; as, however, the head cannot be revolved very fast in this way, we may adjust the lathe centres as before described, and revolve the head as rapidly as possible by hand, and letting it come to rest mark which side is at the bottom, and if on several tests the same side comes to the bottom of the plane of revolution at each test, that side is the heaviest and must be corrected. If it is found to be a flat side or cutter seat that comes to rest at the bottom, the correction can be made by deepening the bolt holes on that side, measuring to see which bolt hole is the shallowest, and making all as nearly as possible equally deep.

If the head has T slots instead of bolt holes, the slots may be cut or filed out to effect the balance, care being taken to make the slot equal in distance from the edges of the cutter seat face.

The next essential in order to have a properly balanced cutter head is that the bolts and nuts all weigh alike, and that the bolts be of the same length. The bolts should be turned to an equal diameter of equal length and threaded for an equal distance along the body of the bolt, and the nuts should be of equal depth and all fit accurately to the same wrench, and the weight of the bolts and nuts when put together may then be equalized by reducing the heads of the heavy ones.

We now come to the balancing of the knives, which must be made of equal thickness and width throughout, with the slots for the bolts of equal widths and depths.

The knives require to be as accurately balanced as it is possible to make them, for otherwise they will cause the head to jar and vibrate violently, thus producing rough work. The knives weighed individually may be of the same weight, and yet the head may run out of balance by reason of one end of a knife being heavier than the other end.

Fig. 3173 represents a machine constructed by J. A. Graham & Co., for balancing planer knives, moulding knives, cap screws, and knives in rotary cutter heads of all kinds.

Let it be supposed that the knives are the same specific weight, but that there is an excess of weight at one end; when revolving on the head, a violent jarring or throwing will be caused by reason of the excess. The knives could be reduced to the same specific weight by the aid of common grocers’ scales, but the ends could not be made the same proportional weight as on such balance.

In the cut s s is the base of the scale; l, m the standards for the support of the scale beams b b and k k.

d, d′ are two pivots of the scale beams.

d is the loop on which the pivot d works.

e is a joint in the loop.

d′, e′, and f show the loop and connection.

c is the sliding table which has the stop c′, and is adjustable for different lengths of knives.

a a is a knife in position for balancing endwise.

g is a slotted piece, and is held to the scale beam by the screw v. The slot in g is shown at g′, and limits the travel of the scale beams.

h is an angular piece fastened to the lower scale beam, and receives the screw j.

i is a small weight used for fine adjustment.

o, o are weights which slide along the scale beam k k, and are held in place by the thumb screws p, p.

n shows side view of weight, which is so constructed as to allow it to be easily removed. In using the machine the lightest cutter or knife of the set is first found and its two ends balanced, by turning it end for end on the scales, and reducing the weight of the heavier end. The other knife or knives are then balanced without disturbing the adjustment of the machine as made for the first knife.