Chapter XXXV: Wood Working Machinery (2)

In ordinary circular saw benches or machines the packing comes about up to the level of the table, as shown in Fig. 3116, in which A is a hand hole for putting in and lifting out the plate B, so as to put in or remove the wooden pieces C, D, upon which the packing rests.

Fig. 3117 represents a saw mill constructed by the Lane & Bodley Company. In this machine two circular saws are employed, the upper one being of small diameter and revolving in the same direction as the log feed. A is the driving pulley for the main saw arbor _a_, and B the driving pulley for the upper saw arbor _b_. The carriage feed is obtained by belt from cone pulley C to cone pulley D, on whose shaft is a friction pulley _e_, which, for the feed motion, is moved by lever E into driving contact with pulley F, whose shaft drives the pinion G, which gears with the rack of the carriage. The three steps on the cones C, D, give three rates of feed, and a quick return motion is given to the carriage by engaging the friction pulley with a wheel not shown in the engraving.

The log to be sawn rests upon the slideway S S´, and is secured thereon by the dogs J, J, which are capable of sliding up or down upon the heads H, H´. When the handles K are raised the slides carrying dogs J are free to be moved up and down H, H´, whereas when handles K are depressed the dogs J are locked and hold the log. The operation is to raise the dog slides to the top of H, H´, set the log up to the faces of H, H´, and then by raising handles K, let the dog slides fall, their weight forcing the dogs into the log, and the depression of K locks the dog slides upon H, H´, respectively.

The log feed is obtained from the lever L, which operates the ratchet wheel T, which drives bevel gears V and W, which operate the screws that slide the heads H, and H´, along the slideways S and S´.

Three rates of log feed are obtained by regulating the amount of motion that can be given to the lever L, the construction being as follows:

In the lever L is a slot in which a stop _r_ can be secured at different heights, and the piece M has four notches. The limit to which L can be moved to the left is until it comes against the stop _x_, but the limit to which it can be moved to the right is governed by the height of the stop _r_ in the slot in L. If stop _r_ is set at its highest position in the slot, L can be moved to the right until the stop _r_ meets the right hand step on the circumference of M, and a maximum of log feed is given.

TUBULAR SAW MACHINE.

Fig. 3118 represents a tubular saw machine. The saw runs in fixed bearings, the work feeding on the table B, running on ways on A. The work is here obviously sawn to a curve corresponding to that of the circumference of the saw.

CROSS CUTTING OR GAINING MACHINE.

In Figs. 3119 and 3120 is represented a machine constructed for either cross cutting or gaining, the gaining head shown on the machine being replaced by a cross-cut saw when cutting off is to be done.

It consists of a vertical column or standard, upon the face of which a slideway A for the arm B, on which is a slideway C, along which the head for carrying the saw arbor traverses.

When the saw is to be used, the carriage or work table must be locked in position and adjusted so that the saw will come fair in the groove, provided in the table, but it is not necessary to dog or fasten the work to the table, because the saw itself draws the work over fair against the fence.

When the machine is used for gaining, the work must be dogged fast to the table, so that the work and table may be moved accurately together and the widths apart of the gains kept accurate.

Joshua Oldham's combination saw for grooving or gaining is shown in Fig. 3121. It consists of two outside saws, such as shown at the top of the figure, and having spur teeth between the ordinary cutting teeth. The tops of the spur or cross-cutting teeth are a little higher than the other teeth, so that they sever the fiber before the ordinary teeth attempt to remove it, and thus produce very smooth work. The inside pieces, shown at the bottom of the figure, go between the two outside saws, if necessary, to make up the required width of gain. They are made 1/8 inch thick, with an odd one 1/16 inch thick, and will thus make gains advancing in widths by sixteenths of an inch.

SCROLL SAWING MACHINES.

The scroll sawing machine derives its name from the fact that it is particularly fitted for sawing scroll or curved work by reason of the saw (which is a ribbon of steel with the teeth cut on one edge) being very narrow.

The principal points in a scroll sawing machine are to have the saw held under as nearly equal tension as possible throughout the whole of the stroke; to render the machine readily adjustable for different lengths or sizes of saws, to provide it with means of taking up lost motion, and to avoid vibration when the machine is at work.

A scroll sawing machine constructed by the Egan Company is shown in Fig. 3122, a sectional view of the saw straining mechanism being shown in Fig. 3123. A, A, is a casting having slides for the head B, which is adjustable upon A to suit different lengths of saws, and is secured in its adjusted position by the bolt C and nut D. To the ends of the springs S, a strip or band of leather is secured, the other end passing around the small step F of a roller R, and being secured thereto. The roller R is so supported that it may rise and fall with the strokes of the saw. A second leather band G is secured at T, passes over the large step of R, and at its lower end hooks to the saw, which is strained by the springs S. This reduces the motion of the springs, and thus serves to equalize their pressure throughout the saw stroke.

The lower end of the saw is gripped in a slide or cross-head that is driven by the connecting rod and crank motion shown in the general view Fig. 3122. The lever shown at the foot of the machine moves the belt to the fast or loose pulley to start or stop the machine, and operates a brake to stop the machine quickly.

Fig. 3120.

Fig. 3121.]

Fig. 3124 represents a scroll saw constructed by H. L. Beach. This machine is provided with a tilting table, which can be set at any angle up to 39 degrees, either to the right or left, the exact angle being indicated by a graduated arc.

The straining device, including the springs, air pump, guide-ways, cross-head and steel bearing, are all attached to the vertical tubular shaft, which is secured to the heavy cast back support by the box E and eccentric lever F. By raising the lever F, the shaft, being balanced, is free to move up or down to suit any length of saw.

At the same time, the steel bearing L forms a support for the back and sides of the saw, and can be raised or lowered to suit any thickness of work.

The under guide-ways are so constructed that their expansion by tightening does not tighten the cross-head. Instead of the ordinary tight and loose pulleys, the crank shaft carries a friction pulley and combination brake by which the saw is stopped or started instantly, by a single motion of the foot.

This leaves the hands entirely free, and saves considerable time in stopping and starting.

The lower end of the saw is held by a steel clamp; when the saw breaks it can be used again by filing a notch. Both ends of the saw are arranged to take up lost motion and wear.

Any desired strain from 10 to 75 pounds can be given to the saw, and the strain is equal at all points of the stroke.

BAND SAWING MACHINES.

The simplest form of band sawing machine is that in which the work is fed to the saw by hand, a machine of this class, constructed by J. A. Fay & Co., being shown in Fig. 3125. It consists of a standard or frame A, carrying the saw-driving wheel B, and the upper wheel C, the saw being strained upon these two wheels. The lower wheel runs in fixed bearings, while the bearing of the upper wheel is carried in a slide provided in the frame, being operated in the slide by a screw, whose hand wheel is shown at E, so that it may be suited for different lengths of saws.

The bearing of the upper wheel is so arranged that the tension placed on the saw may be governed by a weighted lever F, which enables the upper bearing to lower slightly, so that if a chip should fall between the saw and the lower wheel, it may not overstrain, and therefore break the saw.

At J, is a bar carrying a guide G, which sustains the saw against the pressure of the cut, a similar guide being placed below the table T, at G´. This latter guide is fixed in position, whereas the upper one, G, is adjustable for height from the work table, so that it may be set close to the top of the work, let the height of the latter be what it may. G´´ is a guide and shield for the saw at the back of the machine, and H is a shield to prevent accident to the workman, in case the saw should break.

Band saws are ribbons of steel, brazed together at their ends and having their teeth provided on one edge. The widths of band saws vary from 1/16 inch to 8 inches, and their thicknesses from gauge 18 to 22 gauge, according to width.

The advantage of the band saw lies in that it may be run at high velocity, may be made thin, and its cutting action is continuous.

As a band saw is weak, it is desirable to have the teeth as short as possible and leave enough room for the sawdust, so that it shall not pack in the teeth.

In a circular saw, the centrifugal force acts to throw the sawdust out, while in a frame saw, the backward motion of the saw acts to clear the teeth of the dust, whereas in a band saw the dust is apt to pack in the teeth while they are passing through the work. The remedy is to space the teeth widely, thus giving room for the dust without having a deep tooth, an ordinary form of tooth being shown in Fig. 3126.

A stronger form of tooth is shown in Fig. 3127, the tooth gullets being well rounded out, and the teeth shallow at the back, while having ample room in front for the dust.

In determining the shapes of the teeth of band saws, we have the following considerations:

One of the principal objects is to have the back edge of the saw bear as little as possible upon the saw guide, and as the feed tends to force that edge against the guide, we must so shape the teeth as to relieve the back guide as much as the circumstances will permit. This may be done by giving to the front faces of the teeth as much rake as the nature of the work will permit. Thus, in Fig. 3128, it will be seen that from the front rake, or _hook_ of the teeth, as it is commonly called, there is a tendency for the cut to pull the saw forward, this tendency being caused by the pressure, on the teeth in the direction of the arrows, and obviously acting to prevent the saw from being forced against the back guide.

For sawing soft woods, such as pine, the teeth may be given a maximum of front rake or hook, whereas for hard woods, the front faces must be made to stand at very nearly a right angle to the length of the blade, and the feed must therefore be lighter, in order to relieve the back edge of the saw from excessive contact with the back guide, which would not only rapidly wear the guide, but acts to crystallize the edge of the saw and cause it to break.

The set of the teeth of band saws is given in two ways, _i. e._ by spring set, which consists of bending each alternate tooth sideways, as in Fig. 3129, or by swage set (upsetting or spreading the points of all the teeth), a plan that may be followed with advantage for all saws thicker than about 20 gauge.

Spring set is given either by bending, or by hammer blows, and swage set either by blows or by compression. In spring set, each tooth cuts on one side, and there is consequently a pressure tending to bend the tooth sideways, and break it at the root, whereas in spread set, the tooth cuts on both sides equally. As the front faces of band saw teeth are filed straight across, as in Fig. 3129, and are not given any fleam for any kind of woodwork, the set, whether spring or a spread, should be equal in amount for every tooth, and the pitch and depth of the teeth should be exactly alike, so that no one tooth will take more than its proper share of the cut.

The bend or set of the tooth in spring set saws, should not extend more than half way down the depth of the tooth, which will make the set more uniform and save tooth breakage, it being borne in mind, that a tooth hard enough to break if the set extends down to the root, will set easily if it extends half way down only, and that a saw may be soft enough to file, and of a proper temper, and yet break if the spring set is attempted to be carried too far down the tooth.

If as in the case of fine pitched teeth, the teeth are filed with a triangular or _three_ square file but little front rake or hook can be given, without pitching the teeth widely. This is shown in Fig. 3130, in which S, is the section of a saw, and F, a section of a three square file. The front faces have no rake, and the file is shown as acting on both faces.

In Fig. 3131, we have the same pitch of teeth, but as the file is canted over, so as to give front rake or hook to the tooth, the tooth depth is reduced, and there is insufficient room for the sawdust. In order, therefore, to give to the teeth front rake, and maintain their depth while keeping the pitch fine, some other than a three square file must be used.

The principal defect of the band saw is its liability to break, especially in band saws of much width, as say 3 inches and over. A saw that is 6 inches wide will ordinarily break by the time it has worn down to a width of 4 inches. Now for heavy sawing it is necessary that wide saws be used, in order to get sufficient driving power without over-straining the saw.

The causes of this saw breakage are as follows:

In order that the saw may be regulated to run on the required part of the upper wheel, and lead true to the lower wheel, it is necessary that the upper wheel be canted out of the vertical, and band sawing machines are provided with means by which this may be done. If the upper wheel were set level, as in Fig. 3132, the saw itself would be held out of level, and the toothed edge would be more tightly strained than the back edge. Furthermore the middle of the saw cannot bed itself perfectly to the wheel. Furthermore, the velocity of the toothed edge would be greater than that of the back edge because of its running in a circle of larger diameter when passing over the wheels.

This is to some extent remedied by setting the wheel out of the vertical, as in Fig. 3133, in which case the two edges will be more equally strained, and have a more equal velocity while passing over the wheels.

There will still however, be an unequal strain or tension across the saw width, and it is found that unless the saw is made what is known as loose,[48] it is liable to break, and will not produce good work. It is to be observed however, that the above may be to a great extent, and possibly altogether, overcome by means of having the rim face of the wheel, or of both wheels, curved or crowned in their widths, so that the saw will be in contact with the face of the wheel, nearly equally across the full saw width. This would also cause the saw to run in the middle of the wheel width, and thus enable the alignment of the saw to be made without requiring the upper wheel to be set out of level.

[48] See page 69, Vol. II., for what is technically known as looseness
in a saw.

RE-SAWING BAND SAW MACHINE.

A re-sawing machine is one used to cut lumber (that has already been sawn) into thinner boards. Fig. 3134 represents a band saw machine, constructed by P. Pryibil, having a self-acting feed motion, consisting of four feed rolls, all of which are driven, and two small idle rolls, which are so arranged as to guide the last end of the stuff or work after it has left the driven rolls.

Four rates of feed are provided, and the upper wheel can be set at the required angle from a perpendicular while the machine is in motion.

The upper guide wheel, and the mechanism by which it is carried, is counterbalanced by a weight that hangs within the column or main frame, and is therefore out of sight.

The construction of the parts by means of which the upper wheel is adjusted in height to regulate the tension of the saw, and which also cants the wheel out of the vertical, is shown in Fig. 3135, which represents a portion of the main frame or column, on which is a slideway B, for the slide C, which carries the bearing for the upper wheel.

The method of moving the slide C for moving the upper wheel to adjust the saw tension is as follows:

By means of the handle H and the worm and worm wheel at W, the shaft S is revolved. The upper end of S is threaded into the nut N, which is capable of end motion in its bearing at _e_, and which abuts against the lever L, the latter abutting against the end of the screw M, and acting at its other end on the rubber cushion P. Now suppose that S be revolved in the direction denoted by the arrow, and the effect will be to raise the nut N. This effect will be transferred through the screw M to the slide C, which will rise up on B, carrying with it the upper wheel bearing and wheel.

When the upper wheel receives the strain of the saw, then the continued revolution of shaft S will cause the nut N to lift endways in its bearing _e_, the screw M acting as a fulcrum to cause the lever L to compress the rubber cushion P. The amount of tension on the saw is tested by springing it sideways with the hands. Now suppose the saw to be properly strained, and that a piece or chip of wood accidentally gets between the saw and the lower wheel, and the result will be that the slide C will (from the extra strain caused by the chip) move down on its slideway B, which it is capable of doing, because the long arm of the lever L can move down, compressing P, and this will prevent the saw from breaking.

To cant the wheel for leading the saw true to the lower wheel, the following means are provided:

The upper wheel bearing rests on the fulcrum at _a_, and is guided sideways by the screws _c_ and _d_. At _f_ is a stud threaded into the bottom half of the upper wheel bearing, the wheels _g_ and _h_ threading upon _f_. The weight of the upper saw wheel endeavors to lift the end J of the wheel bearing, and wheel _h_ determines how much it shall do so, while wheel _g_ acts as a check nut to lock the adjustment.

Fig. 3139.]

Fig. 3140.

Fig. 3141.

Fig. 3142.]

The feed rolls are carried in slides which are operated in slideways by means of screws, and the two back rolls, or those nearest to the column are maintained vertical. The two front ones, however, are provided with means by which they may adjust themselves to bear along the full depth of the work, notwithstanding that it may be taper. The construction by means of which this is accomplished is shown in Figs. 3136 and 3137, in which A is front and B a back feed roll. The bearings of feed roll A abut against rubber cushions C, C, whose amount of compression is regulated by the set screws D, D.

The construction of the saw guides is shown in Fig. 3138, which is a plan view partly in section. S S are hardened steel plates set up to the saw by means of studs whose nuts are shown at N N. W is a friction wheel which supports the saw against the thrust caused by the work feeding to the saw. The adjustment of the wheel W to the saw is obtained by means of the wheel H.

The hand wheel H operates the screw _r_ _r_, that adjusts the wheel W to the saw, the wheel J serving to lock the screw in its adjusted position.

Fig. 3139 represents Worssam's band saw machine, in which the standard may be set at any required angle for cutting bevels.

When the work is heavy and not easily handled it is preferable to set the standard and saw at the required angle, rather than to set the table at an angle and have the saw remain vertical. In Worssam's machine this is accomplished as follows:

A is the main frame carrying the work table T, and having circular guideways B, B´, which carry the standard C having guide C´ for working in the circular guideways B, B´.

The saw-driving wheel D, is carried in bearings provided in C, and, therefore moves when the standard C is moved.

At the upper end of C, is the slide E, which carries the bearing for the upper wheel F, this slide being adjusted to regulate the saw tension by the hand wheel O, whose screw threads into a nut in the slide E. H carries the front guide G, for the saw, the back guide G´ being carried by a bracket bolted to C. The back guide is fixed in position, but the front one is adjustable to suit the height of the work by raising or lowering it.

The means for setting the saw at the required angle to the work table are as follows:

At the back of the standard C is a rack J, whose pitch line is an arc of a circle of which the axis of the guideway C´ is the centre.

Into the rack J fits the worm wheel K, at the bottom of the shaft of which is a pair of bevel gear wheels L, which are operated by the hand wheel M.

A band saw machine constructed by Messrs. London, Berry & Orton, is shown by Figs. 3140, 3141 and 3142, in plate XXIII. The saw-driving wheel D, has wrought iron arms turned true and screwed into the wheel hub. The wooden segments have their grain lengthways of the rim, and between them are placed pieces of soft wood with the grain across the rim. This acts to keep the joints tight, notwithstanding the expansion and contraction of the wood.

The upper wheel is adjusted for straining the saw, and for leading the saw true, by the following construction. It is carried in a U-shaped frame F, which is pivoted at _y_ to a slide that is gibbed to the main frame, and by operating the screw shown at X, the frame F is set to the required level.

To regulate the tension of the saw, the hand wheel K is operated, which drives the pair of bevel gears J and I, the latter of which operates the threaded shaft H, whose upper end G connects with the slide which carries F. Within G is a spring to act as a cushion to the slide, and thus prevent saw breakage should a chip pass between the saw and its driving wheel.

The saw guide frame is secured to the main frame at _m´_, _m´_. Upon the face of _m_, is a slideway for the saw guide arm _n_, which may thus be adjusted as closely to the upper face of the work as possible.

The weight of arm _n_ is counterbalanced by a rope passing over the pulley V, and supporting the counterbalance weight _w_. The feed motion is constructed as follows:

On the same shaft as the main fast and loose pulleys A, B, is the feed pulley L, which by belt connection drives pulley M, which is on the shaft W, upon which is a friction disc N, by means of which the rate of feed is regulated. The feed disc N drives the wheel O; the degree of contact between these two (N and O) is regulated by means of the weight T, on the lever U.

On the same shaft as the friction wheel O, is a pinion driving the gear X, which is on the same shaft as the pinion Y, which drives the two gears Y´ and Y´´.

Referring now to Fig. 3142, gear Y´ drives the pair of bevel gears Z and Z´, for the feed roll _e_, and the pair of bevel gears shown at Z´´, the feed roll _f_. The gear Y´´ drives similar gearing for the feed rolls _e´_ and _f´_, seen in the plan Fig. 3140.

Referring now to the plan Fig. 3140, and the side elevation, Fig. 3142, the feed roll _f_ is carried in a frame _g_, which is fitted on the slideway _d_, _d_, and receives a screw _i_, upon which is a hand wheel _h_; at the back of this wheel is the lever _j_, which is weighted as shown, so that the force with which feed roll _f_ grips the work is determined by the weighted lever _j_, and may be varied to suit the nature of the work by moving the weight along _j_.

The construction of the gear for feed roll _f´_ is similar, as may be seen in the plan Fig. 3140, _f´_ being in a slide _g´_, which has a screw _i´_, and hand wheel _h´_, a weighted lever corresponding to _j_ acting against wheel _h´_. In proportion as _f_ and _f´_ are opened out to admit thick stuff or work, the hand wheels _h_ and _h´_, respectively are used to screw the screws _i_ and _i´_ into their respective slides _g_ and _g´_, and thus maintain the weighted levers in their requisite horizontal positions. The feed rolls _e_ and _e´_ are carried in slides _c_ and _c´_, and are adjusted to suit the thickness of the stuff or work by a hand gearing, which consists of the hand wheel _a_, seen in the plan and in the front elevation, Fig. 3141, which drives the pinions _b_ and _b´_, which operate screws for the slides _c_ and _c´_, the latter being a left hand screw. The front rolls _e_ and _e´_ are therefore held in a fixed position, whereas the back ones _f_ and _f´_ may open out under the pressure of the weighted levers _j_, and thus accommodate any variation in the thickness of the work.

The rate of feed is varied to suit the nature of the work by the following construction: The friction wheel O and the hand wheel R are connected by a yoke _q_, Fig. 3142, at the ends of which are the joints P, Q, seen in the plan, Fig. 3140. Hand wheel R is threaded to receive the screw S, and it follows that by revolving R, the friction wheel O may be moved towards the centre of the friction disc N, which would reduce the velocity with which N would drive O, and therefore reduce the rate of feed. If the friction wheel O be moved from the position it occupies in the plan Fig. 3140, to any point on the other side of the centre of the friction disc N, the direction of feed motion would be reversed.

A band saw machine for the conversion of logs into timber, and constructed by Messrs. London, Berry & Orton, is shown in Fig. 3143. The logs are fixed to the carriage by dogs and the carriage traverses the log to the feed.

RECIPROCATING CROSS CUTTING SAW FOR LOGS.--The machine shown in Figs. 3144 and 3145 is designed for the purpose of cutting heavy and long logs into convenient lengths preparatory to cutting the logs up in other machines, and it is usually therefore placed at the entrance to the mill, where it is of immediate service as the lumber comes into the building.

The machine here shown is intended for logs up to 36 inches in diameter, is simple in construction, requires very little foundation, is easy to handle, and occupies but very little room.

The saw is here fed mechanically to its cut, whereas in some machines it is fed by its own weight, and therefore requires great care to be taken, when the saw is finishing its cut, in order to prevent it from falling after it has passed through the log.

Fig. 3145 is a side elevation and Fig. 3144 a plan of the machine, in which A is the frame of the machine on which are the bearings for the shaft B carrying the fast pulley C, loose pulley D and fly-wheel E at one end, and at the other, a crank disc F, whose pin is shown at G. This drives the saw K through the medium of the connecting rod H.

The saw is fast at the butt end to along slide J, J, which works in a long guide formed on the face of the swinging frame L, which pivots at one end on the shaft B and at the other is carried by a slide P, on the vertical slideway M, and is fed down the same to give the saw its cut by the screw whose hand wheel is shown at N.

V is a second guide for the saw, and being connected to the slide feeds down with the saw until it meets the log.

A counterweight W balances the weight of the slides and saw, so that there being a pit beneath the balance weight the saw and its guides may be raised so that the saw stands out of the way when not in use. Y is a dog for holding the log, which is also blocked by the wedges Z Z´.

The construction of the main bearing is shown in Fig. 3146, in which it is seen that the hub or boss of the loose pulley is much longer than that of the fast one, thus providing a large amount of bearing surface, which is advantageous because the belt will remain longer at the loose pulley than it will on the tight one. The sleeves or bushes in which the shaft runs afford a simple means of renewal to restore the fit when the shaft has worn loose in its bearings.

It is obvious that as the guide frame L is pivoted to the shaft B, it carries the end of the saw (as it is fed down) in an arc of a circle of which the axis of B is the centre, whereas the slideway M is straight, and slide P therefore moves in a straight line instead of in the required arc. Provision however is made to accommodate these two motions as follows:

Fig. 3147 is a sectional view of the slides on the slideway M and Fig. 3148 a plan of the same. The hand wheel N corresponds to N in Fig. 3145. Upon the vertical slideway (in Fig. 3145) of the standard fits the slide P, which has a horizontal slideway for the slide R, which is free to slide automatically, having no screw or other device to restrain it, save the guide frame L, and therefore as this frame is lowered to feed the saw the slide R moves automatically to accommodate the arc of a circle in which the guide moves on account of being pivoted at B.

HORIZONTAL SAW FRAME.--This machine is designed for the more expensive woods, such as mahogany, and is finding much favor because it will cut at a very high speed, the saw travelling about 150 feet per minute.

Fig. 3144.

Fig. 3145.]

The roughest shaped trunk may be easily fixed on the travelling table, and a thin saw may be used as it may be very tightly strained. This machine is used either for breaking down timber, or for converting it from the log to any desired thickness, the thickness of the boards being very readily and easily varied.

The machine consists essentially of a framework carrying either one or two very thin and tightly strained saws operating horizontally and cutting on both strokes, so that the feed is continuous, the construction being as follows:

Referring to Figs. 3149 and 3150, A is a base plate or bed carrying two uprights or standards B, B, having guideways C, C, for the cross-head D, which has slideways E, E´, for carrying the frame F, F, which carries the saw G, which is guided on each side of the work by the guides H, H´.

The frame F, F is connected to the slides J, J´, and has the rod K, to which the connecting rod pin L is attached, and the rod M, which acts as a stretcher. A connecting rod P, connects the pin L to the crank pin Q, on the crank Q´, which is driven by belt from the pulley T, a fly-wheel being provided at S.

It is obvious that as the crank revolves the saw reciprocates, its line of motion being determined by the guideways E, E´.

The construction of the saw is shown in Fig. 3151, and it is seen that for half its length, the teeth are formed to cut when the saw moves in one direction, while for the other half the teeth slope in the opposite direction, and are therefore arranged to cut when the saw is on the opposite or return stroke, and the construction whereby the saw is enabled to cut on both strokes is obtained as follows:

Fig. 3149.]

Referring to Fig. 3149, the two slides E, E´, on which the saw-carrying frame F F slides, are not in line or parallel one with the other, but each slide is at an angle of about 85 degrees to the line of feed, so that as frame F is reciprocated at each stroke, one end of the saw advances towards the cut, and the other recedes from it, thus causing the saw to cut first on one half and then on the other of its length, one half cutting on the forward, and the other on the return stroke.

The studs or saw-buckles for attaching the saw to the frame are shown in Fig. 3151, in place on the ends of the saw, the part I, that fits in the frame F, Fig. 3149, being squared so that the saw cannot be twisted in tightening up the nuts of the saw-buckle.

The belt works for driving the saw are arranged as follows: at T are the fast and loose pulleys for driving pulley R, the belt passing from T over two pulleys (shown dotted in, Fig. 3149), U, U´, whence it stretches to the crank driving pulley R, whose bearing is provided on the cross-head, so that the two move together when the cross-head is altered in height from the work-table or carriage, to accommodate different thicknesses or diameters of logs.

It is obvious that in proportion as the cross-head is set nearer to the carriage, the belt from T to U, U´ would become slack; provision is made however, to prevent this as follows:

Pulley U, is carried on a frame or swing lever X, to which is attached by rope V the weight W, which therefore regulates the tension of the belt.

The cross-head D may be raised or lowered by belt power or by hand, as occasion may require, the usual course being to move it to nearly the required position by belt power, and then complete the adjustment by hand, a graduated scale being provided as shown, whereby the rack can be set to cut the required thickness of plank without measuring the timber.

The belt motion for raising or lowering the cross-head is obtained by the pulleys at Y, the wheel for the hand adjustment being shown at Y´. In either case the bevel gear wheels Z, Z´ operate, respectively, a vertical screw engaging a nut on the cross-head.

The log feed is obtained by a motion separate from the return motion, there being three rates of feed and a quick return motion, the construction being as follows:

Referring to Figs. 3149 and 3150, a is a belt pulley fast on the crank shaft, and driving pulley _b_, which is also shown dotted in. Pulley _b_ drives the vertical shaft _c_, on which is the cone pulley _d_, having three steps, and which drives (by means of belt _d´_) cone pulley _e_, on which is a worm _f_, driving the worm wheel _g_, which runs idle on its shaft unless engaged therewith by means of the clutch _h_. The shaft of worm wheel _g_ is omitted in Fig. 3149, so as to leave the belt-shifting mechanism for pulleys _q_, _q´_ exposed to view. On this shaft however is a pinion driving the gear wheel _k_, on whose shaft is a pinion _l_, driving the gear _m_, which engages the rack _n_, on the under side of the carriage.

The clutch _h_ is engaged by the lever _i_, to the upper arm of which is attached the rod _j_, _j_, from the lever _p_, hence operating _p_ (which is done by hand), back and forth, throws clutch _h_ into and out of gear with the worm wheel _g_, and puts the carriage feed on or throws it out, according to the direction in which _p_ is moved.

The upper end of shaft _c_ is carried in a bearing on the cross-head, and is provided with a featherway or spline, so that as the cross-head is raised or lowered the upper end of _c_ passes through its upper bearing, and the pulley _b_ travels with the cross-head. The three rates of carriage feed are obviously obtained by means of the three steps on the cone pulleys _d_ and _e_.

We have now to explain the construction of the mechanism for traversing the table back, and giving it a quick return motion, or in other words a quicker motion on the back than on the feed traverse, and this is arranged as follows:

_q_, is a fast and _q´_, _q´´_, are loose pulleys, one driven by an open belt _r_, Fig. 3150, and the other by a crossed belt _r´_, from a countershaft. The belt-shifting forks are operated by lever _s_, whose upper end engages with the rod _t_, which is operated by the lever _u_.

The loose pulleys _q´_ and _q´´_ are twice as wide as the fast pulley _q_.

Now suppose that lever _u_ is moved to the right, and the belt would be moved from the loose pulley _q´´_ to the fast pulley _q_, while the other belt would merely be moved or shifted from one to the other side of loose pulley _q´_.

Similarly if lever _u_, be moved to the left, the belt on the loose pulley _q´_ will be moved on to the fast pulley _q_, and the belt on pulley _q´´_ would simply be moved across the face of the pulley, and as the countershaft pulleys for the two pulleys are of different diameters, therefore two rates of motion are obtained.

The shaft _v_, on which pulley _q_ is fast, drives the pinion _l_, which drives _m_, the latter gearing with the rack beneath the carriage.

The carriage is guided by the wheels _z_, which are secured to it, and run on the iron guideways _z´_, the flanges of the wheels preventing side play, and causing the carriage traverse to be in a straight line.

WOOD-PLANING MACHINES.

The simplest form of planing machine for wood work, is the hand planer or buzz planer, as it is termed, an example of this class of machine being shown in Fig. 3152, which has been designed and constructed by George Richards, for the use of pattern-makers.

It consists of a frame carrying a revolving shaft, which is by some called the _cutter head_, and by others the cutter bar, and to which the cutters or knives are attached.

The work is rested upon the work table, or else pressed against a guide or _fence_, and fed by hand over the revolving knives, whose cutting edges protrude above the surface of the table, to the amount of the depth of cut it is intended to take.

In this example, however, the table is made in two sections, the front one of which is below the cutter edges to an amount equal to the depth of the cut, and the back one level with the cutter edge, when the latter is at its highest point in its path of revolution, the construction being shown in Fig. 3153, in which J, J, represents the top part of the main frame of the machine, C the cutter head, B the front or feed table, A the back or delivery table, and W a piece of work being fed in the direction of the arrow.

Upon the upper surface of the frame J, J, and on the feed side of the cutter head is the carriage G, to which are pivoted two links L, L, which support the feed table B. At D is a hand wheel whose screw has journal bearing in a lug from the table, while the screw threads into a nut provided in the carriage. Obviously then by operating the hand wheel D, carriage G is moved along the top of the frame J, and the height of table B is adjusted. Thus if the carriage G is traversed to the left, the link L would fall more nearly to a horizontal position, and table B would lower. Or if G were moved to the right, links L would stand more nearly vertical, and table B would be raised, it being understood that table B is not permitted to move endways. Similarly by means of hand wheel C, carriage H may be moved to adjust the height of table A.

By this construction, the work can bed fairly on the delivery side, as well as on the feeding side of the cutter head, which is not the case when a single table is used.

It is obvious that the work must be fed in opposition to the pressure of the cut, which endeavors to push the work back from the cutter, and this limits the size of work that the machine can operate upon.

The work can be fed easier however, with a cutter skewed or set out of line with the axis of the cutter head. Thus in Fig. 3154, is the common form of cutter head, carrying two knives placed diametrally opposite, so that the weight of one counterbalances that of the other, and the head will therefore run steadily and smoothly. The knives K, K´ are here set parallel with the axis of the cutter head, hence the whole length of the cutting edge meets the work at the same instant, and a certain amount of time must pass after one cutting edge has left the work before the other cutter edge meets it.

This is remedied by the construction of cutter head shown in Fig. 3155, in which three cutters are used, and each cutter is set askew, or out of parallel with the axis of cutter head, so that the knife begins to cut at one end, and the cutting action gradually extends to the other, hence the cutting action is more continuous and uniform, and better work is produced, while less power is required to drive and feed the machine.

Fig. 3156 shows a cutter head with two skew cutters.

The cutter head is provided with a cover or guard, which is arranged as follows: In the table is cut a groove or slideway, in which a slide fits, and to this is attached a thin sheet-iron guard. To the slide is attached a weight, which draws the guard back to the fence after the work has passed over the cutter head. By this means the guard covers all the knife edge that protrudes beyond the work, no matter what the width or thickness of the work may be; the guard can however be fixed in position when a number of pieces of the same size are to be planed.

The fence provides a guide surface for the work, and its face may be set at any required angle to the surface of the work table. Suppose, for example, that the sides or edges of a piece of work require to be at an angle of 100 degrees to the top and bottom surfaces, then the top surface may be planed first, and the fence being set at an angle of too degrees to the table surface, the top of the work may be pressed to the surface of the fence while fed across the cutter, and as a result, the side or edge will be planed at 100 degrees to the top.

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 1/100 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.