HUNTER'S STONE-PLANING MACHINE.

Among the few exceptions to the universality of steam-power as a first mover, which existed a year or two ago, by far the most important was its very limited applicability to the cutting, dressing, and fashioning of stone. Many attempts had been made-some of them by machinists of first-rate eminence-to construct a steam-power machine which should supersede the mason's hand-mallet and chisel; but one and all had proved entirely abortive. Difficulty there was none in contriving steam-machinery that would slice or hew in pieces, and even with great nicety, the stoutest blocks which the quarry could furnish; but the difficulty lay in this, that the immense friction to which metal points or edges are subject, when brought with great force and in rapid succession into contact with so hard and gritty a material as stone of every description, caused so prodigious a waste in tools, that it far more than counterbalanced any advantage that could result from superior celerity of execution.

The merit of overcoming this serious objection, and of adding thus one more to the triumphs of the steam-engine, belongs to Mr. James Hunter, the Superintendent of the Leysmill Quarries, near Arbroath. After several years of thinking and contriving, and experiments without number, he has invented a power stoneplaning machine, which is so ingeniously and judiciously contrived, that it cuts and dresses the largest blocks of stone not only with as much exactness as can be done by hand, but with so little injury to the tools, and with so much rapidity, as to leave all land-labour, in point of economy and dispatch, at an immeasurable distance.

We have before presented our readers with some samples of the wonderful capa bilities of this machine (see the Report of Messrs. Carmichael and Kerr, C.E., published in our 612th Number), and we are glad to have it now in our power to lay before them the first description which has appeared of the machine itself, to which we shall add some additional information of great interest which we have been favoured with by the patentee respecting its performances.

The engraving (fig. 1) on our front page represents a plan of the machine as it appears in its complete state when fixed and ready for working, to a stone bed or foundation; and fig. 2 is an end eleva

tion thereof. The steam-engine employed is omitted in both views.

The machine, of which A A is the sole or foundation plate, consists of three principal parts; first, a platform, which carries the stones to be planed; second, two tilt or cant blocks, which hold the planing tools; and, third, a traversing-frame, in which these tilt or cant blocks are fixed, and by means of which the tools are. brought into action against the surface of the stones.

1. The platform for the stones. On the sole or foundation plate A A, three rows of traverse-rollers a aa are fixed. BB is the platform on which the stones CC are laid; it moves to and fro on the rollers aa, and is formed of planks, four inches thick, laid across three longitudinal beams DD, and securely bolted thereto. The two parallel bars bb nailed to the surface of this platform are about an inch thick, and faced with plate-iron; they serve as ledges within which to secure and steady the stones CC, by means of loose chocks of wood of different sizes. Where the longitudinal beams DDD of the platform rest or bear on the traverse-rollers aaa, they are strengthened to meet the extra pressure by under-plates of iron eee. the bottom of the central beam a toothed rack ƒ is fixed, which extends from end to end.

Το

2. The cant or tool blocks. BK, BK, are two blocks fixed into the traversingframe, one on each side, with two tools ili2, k1 k2, in each. Fig. 3 is a frontview, and fig. 4 a side-view, of these cantblocks, on a larger scale than in figs. 1 and 2. They turn on studs hh, which are fixed in vertical sliding-blocks mm, which are moveable up and down by the screws and handles nn, so as to be adjustible to any thickness of stone that may be required to be cut. The two tools marked i1 and k1 are roughing tools, and those marked i2 and k2 are finishing tools. All are of a round form, and about an inch in diameter; the two finishing ones have chisel or broad mouths. Both sets of tools are fixed in wrought-iron tubes oo by means of adjusting screws pp, which tubes are turned so as to fit accurately into holes bored in the cantblocks BK. To each set of tubes in which the finishing tools are fixed a short lever q is keyed on, the upper end of which is slightly curved and toothed, and above it there is a horizontal screw r,

which works into the teeth of this lever q, so that by applying a spanner to the square head s of the screw r, the finishing tool may, through the medium of the screw, the lever, and the tube, be adapted with the greatest nicety to the surface of the stone to be planed and dressed. No such nice adaptation is necessary in the case of the roughing tools, and to them, therefore, no such adapting lever is applied. G, fig. 3, is the cover for the pivots of the screw r. Two brackets are affixed to the face of the vertical sliding-blocks mm, in the manner represented in fig. 1, and two screws, t and u, are inserted therein, which screws serve to limit the arc described by the cant-blocks BK, B K, in turning on the studs hh, as afterwards more particularly explained.

3. The traversing-tool frame. LL is a large sliding-frame, in the centre of which the working or planing tools are fixed, and which has a space of about six feet to traverse in, three on each side of the position in which it is represented in the engravings. This frame rests on four wheels or friction-rollers MM MM, affixed to the shafts N N, which revolve in brackets 0000. PP are two pulleys, which revolve on an axis fixed in the standards GG, one of which is worked by an open strap, and the other by a cross strap, so that they may revolve in opposite directions, and thus give a reciprocating motion to the frame LL. Qis a clutch between the pulleys PP, connected with the handle and crank RR, which are acted upon by studs or catches S1 and S2, projecting from the sides of the sliding tool-frame LL in such manner as to make the clutch operate on each tool alternately. T is a pinion fixed to the end of the axis of the pulleys PP. U, a spur-wheel, into which the pinion T works, V the axis of this spur-wheel, on which axis there is fixed a pinion (not seen in the engravings), which works into a sliding-rack WW, the teeth of which point downwards. XXXX are the bearings on which the rack W W slides. Y Y is a strong beam fixed across the back of the rack W W, the ends of which project through the sides of the slidingtool frame L L. ZZ are two connectingrods, which pass from the ends of the beam Y Y to the blocks in which the planing-tools are fixed, as before explained. E is a pinion, which works in the toothed rack f on the under side of

the central longitudinal beam of the platform B. F is a shaft, to one end of which the pinion E is fixed. G is a ratchetwheel, near to the opposite end of the shaft E. HH is a pall and crank attached to a cross shaft, supported by the standards 11, which acts on the ratchetwheel G. I is a pin, fixed in the side of the traversing-frame LL, and which, as that frame moves towards the side Gz, catches the upright arm of the crank H, and presses it forward in that direction. K is a wheel, which, operating through the intervention of the shaft F, pinion E, and rack ƒ on the platform B, throws it entirely back when all the stones upon it have been planed, or returns it under the planing tools if any part of the work requires to be gone twice over.

The mode of operation requires but little additional explanation. The platform being filled with blocks of stone, the vertical blocks mm are so adjusted that the roughing tools shall strike each block of stone as it passes under them, at such a depth below the top surface, as to sever and throw off before them large portious of the stone at a time, taking care always that the depth shall be within such limits as that the line of least resistance shall terminate in the top surface of the stone, so that the fractures shall all tend in that direction. When this adjustment has been made, the sliding-frame LL is to be moved towards Ha, and as it traverses in that direction the sliding-rack W W carries the cross beam Y Y in the same direction, until the connecting-rods ZZ have drawn the cant-blocks over as far as the screw t, when the roughing tools i1 and k1 will be brought into operation against the stone, and so continue till the projecting stud or catch S1 comes in contact with the crank R, and throws the clutch off the pulley then in operation on to the other pulley, which will make the frame return in the opposite direction Gz. The sliding-rack W W carries back at the same time the cross beam Y Y, till the connecting-rods ZZ push the cantblocks over against the screw u, when the tools i1 and k2 are brought into play, and so continue till the catch S2 comes in contact with the crank, and again reverses the motion. At the moment of this last reversal of the motion taking place, the projecting pin I also throws over the upright arm of the pall and crank H H (in a manner similar to the yard-beam of a

power-loom), and brings forward the platform B with the stones for the next operation of the planing tools. The pall and crank HH falls back of its own weight into its former position, as soon as the pin I recedes from it. When the roughing tools are first brought into action, through the traversing of the frame LL towards Hax, they commonly leave the surface of the stones in ridges, but the finishing tools being farther back, take off these ridges when returning, and so on till the planing of the blocks is completed.

No time is lost in clearing the platform of the finished blocks, as the men in attendance on the machine are removing the blocks at one end while the machine is at work at the other, and a minute or two suffices to return the platform. The frame LL generally traverses at the rate of 30 feet per minute, and a set of stones filling the platform from end to end, can be planed in about 45 minutes. As each tool wears it can be readily removed for the purpose of being repaired, or replaced by new tools by loosening the adjustingscrews pp.

The master feature of the invention appears to us to consist in the means provided for so adjusting the roughing tools (which have the roughest part of the work to perform), that they shall strike the

blocks of stone as they pass under them, › not upon the surface, as usual, but at such a depth below it, that the surface is driven off in large portions at a time. Not only are two or three tools thus able to do the work of a great many,* but the tools have time given them between each stroke to cool; or, to speak more properly, the strokes are made at such intervals that the tools never get sufficiently heated and softened to lose their original tempering. And hence this somewhat paradoxical consequence, that the greater the thickness of surface which the tools have to cut away, the greater will be their efficiency and the less they will be injured; for the lengths of stone driven off at each stroke will always be proportional to the depth of the cutting, and the rest given to the tools in exactly the same ratio. We are informed that, in point of fact, the wear of iron is less by one-half in taking off two inches at a time than in taking off half an inch.

Another valuable though subordinate feature of the apparatus, is the ingenious manner of securing the tools in their places-the union of absolute fixedness

In a stone-planing machine lately patented, the capabilities of which were much talked of for a time, there were no less than from 30 to 40 tools, to be applied in rapid succession to the stone.

while in operation, with the greatest facility for removing them as they are worn out and required to be repaired or replaced. The shaking or recoil after each stroke of the tools is stated to be so small, as to be hardly perceptible to the eye..

An important consequence of the equability of the force applied to the tools is, that the facing given to the stones by this machine is much smoother and sounder than any facing which can be given by the mallet and chisel. The surface of hand-wrought stones is always so bruised, or, what is technically called dazed, to a certain depth, through the unavoidable varieties of strength and direction with which the chisel is applied, and this dazed portion has all to be rubbed off by the polisher before a sound face can be obtained. But in the case of the machine-planed stones, the surface is left in so nearly sound a state, that the labour and expense of after-polishing is reduced more than one-half.

The stones, to the cutting and dressing of which this machine is advantageously applicable, must not, of course, be any of an exceedingly precious descriptionnone of the rarer marbles for examples; but such as exist in so great abundance, that an inch more or less cut away from a surface is of no consequence, and such too as acquire their chief value from the labour bestowed on extracting them from the quarry, and dressing them for use. The sorts of stone to which the patentee considers it to be most applicable, are sandstones, limestones, and freestones in all their varieties.* The power and ve locity requisite vary considerably, according as the stone is soft or hard. Thus, for example, the Arbroath, which is a sandstone of very close and firm grain, admits of a degree of speed many times greater than some of the softer sandstones; and requires a power just so many times less. Again, stone harder than the

We are authorised by the patentee to state, that if any proprietor or lessee of a quarry, who may be desirous of trying the applicability of the machine to any particular species of stone, will forward a block of it in a rough state (carriage free) to Mr. Hunter (Leysmill, near Arbroath), it will be returned to him planed and polished, along with an accurate report of the time occupied in the work, power applied, wear of tools, &c. Or, parties sending to Mr. Hunter two blocks capable of being turned into vases, according to patterns or drawings sent therewith, will receive in return one vase along with a report, &c. free of charge...

Arbroath would require both the strength of the machine and the power of the steam-engine to be proportionally increased.

During the last summer there were six of these machines at work in the Leysmill Quarries, which planed upwards of 170,000 feet of pavement. They are worked by one steam-engine of 6-horse power, which has to work besides two inclined planes, up one of which the stones are dragged from the quarry to the machines.

We have before spoken of the Report of Messrs. Carmichael and Kerr, C. E., on the performances of these engines, and must here content ourselves with referring our readers to it for some very important and satisfactory details on this head. The attention of the Highland and Agricultural Society of Scotland having been drawn by one of its members to this Report, their Secretary was directed to request W. F. Lindsay Carnegie, Esq., the Proprietor of the Leysmill Quarries, to favour them with "a statement showing the comparative expense of machinedressed stone and that dressed by hand.". The following is an extract from Mr. Carnegie's answer to this application :—

"In the first place, looking at the Report of the engineers (Messrs. Carmichael and Kerr), it will be seen that the wages of the people employed in dressing 4,400 feet, amounts to 6l. 15s. 6d.; this includes the wages of all employed in laying on, dressing, turning, and taking off the stones, and also the wages of a person employed in repairs and the construction of additional machinery. To the above may be added for coals 15s. (our local situation enhances this item consider ably), and for interest of fixed capital, and wear and tear about 21. then stand thus:

The calculation will

..£6 15 6

0 15 0 2 0 0

9. 10 6

about four-tenths of a penny per foot. It is more difficult to state what the exact cost of dressing the same stones by hand would amount to. I may say, however, with perfect safety of being within the mark, that the stones in question could not have been dressed by hand at less than four times the cost by the machine, and that this