Part 23
It has been already stated that for the production of spiral work revolving cutters are preferable to fixed ones, unless, indeed, it is required to finish up a perfectly round thread, when Figs. 3 and 4 of the tools drawn are required. Revolving cutters must be placed in the frame of the universal cutter and set to the rake of the thread. Drills may be used for the reciprocating movement, as they make very clean work, and the rake need not with these be attended to. In face work drills are specially to be used to produce patterns like Fig. 325, and others derived from this simple one. An additional apparatus, represented in Fig. 323, is required for the latter process, to enable the rest to be turned in its socket so as to face the work, and notwithstanding the alteration of its position still to keep up the gearing of the wheels. A rest socket to be made and mounted as usual is fitted with a stem surmounted by an accurately drilled boss A, through which passes a spindle fitted with the wheel C, to gear with that on the arm carrying the change-wheels, and which may be changed for one of larger or smaller size. This is for cutting such work as Fig. 324, representing, of course, only a single spiral, very open and of itself of no beauty, but which by intersection of other spirals can be converted into a pattern of great elegance. When it is desired to produce the waved spiral the eccentric is fixed to the rod instead of the wheel C, and the work proceeds the same as when a cylindrical surface is to be worked. In the Fig. shown the division plate of this chuck is of course used.
It is evident that the variations producible by working intersecting spirals and waved lines are very numerous, and these may be additionally varied by the combination of eccentric and spiral movements.
The following six patterns are re-engraved from Valicourt's Hand Book, which is almost identical with that of Bergeron. They were not engraved in time to be inserted under the head of eccentric chuck work. The notation and description annexed is from a manuscript book kindly lent to the writer by an amateur. "_Bed-plate_," 4 deg., must be taken to mean that the work is shifted (on one of the beds of the chuck) four of the marked divisions for eccentricity, counting from the axial line of the mandrel.
"_Slide rest_, 4 deg.," means that the cutting tool is moved four corresponding divisions in its bed for radius of the circle to be cut; and so throughout.
"4 *," means four times repeated.
The cutting tools, unless otherwise expressed, are double angled, and "25 cutting tool," means 25 deg. of cutting edge.
Holtzapffel's scale of divisions is
The scale used in Valicourt is which is that here quoted.
If bed-plate and slide rest are both equally diminished at each cut, a shell results, with the close part internal. If bed-plate is increased and slide rest diminished, the close part of the shell is external.
SPECIMEN I.--Tools 25, 32, 36; Click-plate 96 or 288.
Bed-plate moved. Slide rest moved. Circles done. Tool.
3 2 12* (1 done 7 missed) 25 6 1 12* (1 done 7 missed) 10 3 48* (1 done 1 missed) 36 3 16 24* (1 done 3 missed) 23 4-1/2 4* (16 done 8 missed) 29-1/2 2 96* 25 33 1 96* or 33 5/8 288*
SPECIMEN II.--Tools 28, 36; Click-plate 288.
Bed-plate. Slide rest. Circles done. Tool.
1 1/2 12 28 4 1-1/2 12 7-1/2 2 4 (8 done 4 missed) 36 13 3-1/2 24 28 19-3/4 3-1/2 4 (16 done 8 missed) 36 19-3/4 1/2 4 (in spaces) 21-3/4 1 4 (above last) B 17-3/4 m 1 4 (below last) 36 30 1/2 12 (20 done 4 missed) 28
29-3/8 1/2 12 {( 1 " 18 " ) {( 1 " 4 " )
28-3/4 1/2 12 Ditto. 28-1/8 1/2 12
27-1/2 1/2 12 {(15 done 4 missed) {( 1 " 4 " )
26-7/8 1/2 12 {( 1 " 18 " ) {( 1 " 4 " )
26-1/4 1/2 As before 25-5/8 1/2 Ditto. 25 1/2 12 (20 done 4 missed)
From B to here, border, if with 96 click-plate, not good-looking; tool a boring-bit.
33-1/16 7/8 12 (7 done 1 missed)
31-9/16 13-16th 12 {(1 " 5 " ) {(1 " 1 " )
29-1/16 3/4 12 {(1 " 1 " ) {(5 " 1 " )
27-9/16 11-16th 12 {(1 " 1 " ) {(1 " 5 " )
25-3/4 3/4 12 {(1 " 1 " ) {(7 " 1 " )
SPECIMEN III.--Click-plate 96.
Bed-plate. Slide rest. Circles done. Tool. 1-1/4 1-1/8 8 36 4-1/4 2-1/8 24 5-1/8 11-3/4 24 21-1/2 4-3/4 96 27-3/4 1-1/2 96 28
SPECIMEN IV.
The centre of this is a star of six curved rays, described by fixing the cutter at the centre and turning the mandrel by hand through so many divisions--for convenience so many 48ths of the circumference. These rays are marked by B. (The segment stop is constructed for this very kind of work, and is to be used in the present case):--
Bed-plate. Slide rest. Arcs done for star. 5 B 5 6 (12/48ths of the circle) 5 B 5 12 (11/48ths " ) 5 B 5 12 (10/48ths " ) 5 B 5 12 ( 8/48ths " ) 14-1/8 5 24 (2 done, 2 missed) 19-3/4 1/2 96 24-1/4 4 32 29-1/2 2-1/2 32 (intersecting) 30-1/2 2 32
SPECIMEN V.--Catherine wheel; tool 28.
The ground grailed by concentric circles contiguous to each other. The arcs by fours, all of same radius.
Bed-plate. Rest. Arcs done. 0 1/2 3/4 1-1/4 &c. (for grailing) B 30 30 12 (16/48) (Repeat at three next divisions.)
SPECIMEN VI.--Tools 28, 36; Click-plate, 288.
Bed-plate. Rest. Number. 1-1/4 1 8 done B 12 12 12-7/48 (to meet next circle) 4-3/8 17 24 30 1/2 12 29-1/2 1 12 (On same radius as the last, and surrounding it.) 29 1-1/2 12 28-1/2 2 12 28 2-1/2 12 27-1/2 3 12 27 3-1/2 12 26-1/2 4 12 23-1/2 1 12 (3 done, 21 missed between last, or if click-plate 96.) 25 1 12 (between last)
Although in the matter of beauty the patterns here given are by no means comparable to many others, especially to some lately published from blocks cut by Mr. George Plant, for the _English Mechanic_; they are, by their comparative simplicity, well selected to give the learner a good idea of designing and working with the eccentric chuck. It is not, indeed, proposed by the writer to multiply patterns, as mere copying of such is of small interest to those who are really endued with taste and skill; and the variations producible by combinations of different numbers of divisions of the click-plate and slide rest are of such infinite number, that printed designs of a score or two would not serve to teach the nature of this work better than the half dozen now before the reader. When a new chuck, indeed, is brought out, it is well to give a few specimens of its work, to show the possible purchaser its value as a means of ornamentation and the extent of its capabilities; but when these are understood, the purchaser had much better design for himself, instead of becoming a lazy imitator and copying patterns laid down by others. Details of designs that are presented in a tabular form remind us sadly (for we are married) of the old "_knit one, drop two_," "_purl_" or some such mysterious and, to us, detestable jargon wherewith ladies were, or are, wont to worry the ears of mankind.
* * * * *
The chuck of Professor Ibbetson, and the elliptic cutting frame of Captain Ash, are not introduced here, partly because this work has reached its intended limit, and partly because the inventors themselves have published separate works entirely devoted to a description of the arrangements and capabilities of their respective chucks. A brief notice is appended of Plant's geometric chuck, contributed by the inventor to the pages of the _English Mechanic_.[24]
[24] See Appendix.
* * * * *
The author now concludes his pleasant labours, the result of which is contained in the preceding pages. These labours have been lightened, and the work itself benefited, by several kindly-written remarks received from various readers of the _English Mechanic_, while the articles were in course of production in that paper. Criticisms and suggestions also came to hand in which no such kindly feelings appeared. These also have, nevertheless, had an equal share of attention, and where they appeared to be of value they have been turned to profit, and have resulted in various more or less important alterations and additions. "The Lathe and its Uses," thus re-arranged and modified, must now take its chance in the world with other productions of a similar character; and the writer hopes it may suffice to help those who need such assistance, and may be well received by others who though able to walk alone may yet cherish a kindly feeling for the friendly walking-stick.
APPENDIX.
PROFESSOR WILLIS'S TOOL HOLDER FOR THE SLIDE REST.
This--described and drawn first in "Holtzapffel's Mechanical Manipulation," to which work the author, and, indeed, most authors of books of the nature of the present, are indebted for much of their information--is now become very general, and from its perfect action ought to be universally used in all factories in which the lathe bears a part. It permits the tool to be set at any required angle upon the bed of the slide rest, and holds it securely when placed in position. It is likewise so constructed as to be easily removed from the table of the rest, so that other forms of apparatus may be attached if desired. One nut only has to be turned to fix the tool, this nut turning on a strong central screw, A, in the figure, the lower part of which, as far as the shoulder, is screwed into the top plate of the rest. This shoulder is directed to be made with flattened sides, so as to be capable of being unscrewed by the application of a wrench. The actual clamp is a triangular piece of cast or wrought iron, B, in the centre of which is a hole to allow this piece to go easily over the screw. The hole is hollowed out into a cup-shaped cavity, into which fits a hemispherical washer, shown at C in the section. The clamping nut, D, acts upon this washer, which permits the triangle to take up a position not _necessarily_ quite parallel to the bed of the slide rest, and thus a tool whose upper and lower surfaces may not be strictly parallel will be securely grasped. The piece called triangular is not precisely of that form, but of the shape shown in the second figure, in which E, E, represent two hard steel pins, slightly projecting--one of these, E, appearing in the first figure. These pins rest upon the upper surface of the tool. At the third angle the clamping piece is drilled and tapped to receive a screw, which must work stiffly in this hole. Thus when a tool is placed in position, as shown, the clamping nut maintains a pressure upon the three points beneath the apices of the triangle. As thus arranged the tool would be stiffly and securely held; but Professor Willis has added a second triangular piece, nearly similar to the first, except that it is provided with a boss, in which a notch or groove is cut, K, in both figures, into which the point of the small screw falls. This lower triangle, which is free to revolve round the central screw, is also cut away at the line L, L, of the second figure, so as to form a guide or rest for the side of the tool, which is thus kept at the same distance from the central screw, and placed in a moment exactly under the studs or points of the upper plate. A careful inspection of the two drawings will make the precise arrangement clear. In _making_ it, which is not very difficult, care must be taken to make the triangle of such size and so to place it, that no angle can overhang the top plate of the rest, in whatever position it may be. The hole in the upper triangle or clamp must be tolerably large and slightly conical--the base of the cone upwards, to allow this piece to take up a bearing, as described. The hemispherical washer is always in a horizontal position, and the hole through it may be only of sufficient diameter to allow it to pass freely over the central screw.
MUNRO'S PLANING MACHINE TO BE ATTACHED TO THE LATHE, AND WORKED WITH THE FOOT.
In the _English Mechanic_ of Nov. 2, 1866, a brief notice was given of the above. The author of the present work having carefully inspected the machine and seen it in operation, considers it of such great value to the amateur mechanic, as well as to the professional turner of metal work, that he has had an engraving of the machine carefully made from a photograph, and has here appended it to illustrate the description given.
It is a lathe for planing, cutting key-grooves in wheels, collars, &c., and cutting racks on the teeth of wheels. The lathe is of the usual construction, but outside the right hand standard is fixed a vertical spindle, which is made to rotate by a pair of bevel wheels, the pinion being fast to the end of the crank shaft, and in contact with a wheel of double the number of teeth on the vertical spindle. On the top of the latter is a crank-plate, which will give a stroke of ten inches or less at pleasure. The planing-machine is fixed by two bolts to the lathe-bed, and a connecting rod is attached to the sliding plate or bed of the planing machine, the other end of which is made fast to the pin of the crank-plate. The work is clamped by simple means to this sliding bed, and thus passes to and fro under the tool which, by self-acting gear, is made to traverse sideways after each stroke as in the large planing machines. The whole works almost noiselessly and with the greatest ease, each part being accurately fitted, and the whole well finished. For such purposes as planing the face of the slide valve and its bed in small engines, or shaping the guide bars of eccentric and other chucks, facing the frames of slide-rests, &c., it is exactly what is needed by the amateur, rendering the workshop complete for all purposes without the necessity for adding a large and separate planing machine, which takes up room that cannot always be conveniently spared. With such a lathe as that in the frontispiece, fitted with one of these planing machines, there is scarcely a model of machinery that could not be made. Any of our readers interested in mechanics would be wise to trip over to Lambeth and view the machine in operation; and the writer will guarantee, not only the most civil and obliging attention from the inventor, but the greatest pleasure and satisfaction from the working of the machine itself. There is a _simple arrangement_ for key-grooving and slotting, by attaching the upper slide of the ordinary rest to the crank plate of this machine, in which case most of the apparatus is removed.
HICKS' EXPANDING MANDREL.
Mention of this has been made in the body of the work. It is used for turning rings and washers, and various sizes of these can be turned upon the same mandrel, so that a set of three will suffice for all the work likely to be met with even in the largest factories. Fig. 1 represents the mandrel complete. F, F is the central part, with a conical boss, A, cast upon it, and the whole turned with great accuracy. Four longitudinal dovetailed slots, seen plainly in Fig. 3, are then planed in the conical part, and into these are fitted steel wedges, Fig. 2, A and B, and B, Fig. 3. C, Fig. 1, is a hollow conical washer, which can be advanced over the central part when driven forward by the nut D. This washer, acting on the ends of the sliding wedges, causes them to move towards the large end of the cone A, and, from the form of these and of the cone, any washer or ring will be held tightly when placed outside these wedges, and will also be mounted concentrically.
TURNING SPHERES BY MEANS OF TEMPLATES.
It is but right to state that the above method has been objected to by a practical workman, whose business has led him to study the matter closely. He states that it is impossible in this way to effect the desired object. As the writer has not been able to test the working of the apparatus on his own lathe, he felt inclined, at first, to withdraw the whole chapter. The objections offered, however, were not, to his mind, entirely satisfactory; and the opinion of other equally scientific and practical men being favourable, the chapter has been retained. It is possible, nevertheless, that there may be a mathematical reason which the writer is not competent to work out, and the objector being a man of great mechanical knowledge and experience, his remarks are worthy of consideration. The practical (not insuperable) difficulty appears to be the production of a proper tool for this work.
PLANT'S GEOMETRIC CHUCK.
This chuck is put in motion by an entirely new method; none of its parts being attached to the lathe head, the whole can be put in motion or released in an instant, and without stopping the lathe.
The whole of its work is executed by the continuous motion of the lathe, so that, when the chuck is adjusted, any figure (no matter how complex) may be begun and completed without once stopping the lathe.
By the different arrangements and adjustments of the chuck and slide rest, an infinite variety of the most beautiful geometrical figures may be produced; and some of them of so strange and fortuitous a nature as to bid defiance to any imitation.
_Description of the Drawings._
Fig. 1 is a front view, and
Fig. 2 a view of the back of the chuck.
A A. The foundation plate screwing on the plate of the mandrel and carrying the whole of the other parts of the chuck.
B, C. The two driving wheels giving an independent motion to the chuck.
D. Angular wheel moving freely on the wheel C for the angular adjustment of the figures.
E. Pinion of any number of teeth fitting on the shaft carrying D and C.
H. Large wheel of 120 teeth, forming the foundation of the second part, and driven from the pinion E by the wheels F, G, and T.
L. Large wheel of 96 teeth driven by the pinions and wheels U, I, J, K, and forming the foundation plate of the third part, M, which carries the nose of the chuck.
N, N. Self-adjusting radius plates for carrying the various change wheels.
O, P. The eccentric slides of the first and second parts.
Fig. 2 shows the arrangement of the driving wheels and pinions on the back of the chuck.
The working of the chuck is as follows:--
If the pinion E has 20 teeth, and is geared direct into the wheel H, by means of an intermediate wheel, it will give six loops inwards if the motions are similar, and outward loops if the motions are contrary.
If the wheel H is driven from the pinion G it will give 12, 24, or 48 loops.
Pinion of 24 teeth will give 5, 10, 20, or 40 loops.
Pinion of 30 teeth will give 4, 8, 16, or 32 loops.
Pinion of 40 teeth will give 3, 6, 18, or 36 loops.
Pinion of 60 teeth will give two loops inwards, if the motions are similar, but, if the motions are contrary, it will produce an ellipse of any proportion from a straight line to a circle.
Other combinations will give circulating or overlaying loops.
By the different arrangements of wheels and pinions on the plates N, N any number of loops can be produced up to 2,592 in the circle.
On the opposite page we illustrate some work executed with this chuck by Mr. Plant.
Fig. 3 is a side elevation of the chuck full size.
A, A, the foundation plate screwing on the nose of the mandrel, and carrying the whole of the other parts of the chuck.
B, C, the two driving wheels giving an independent motion to the chuck.
D, D, angular wheel moving freely on the wheel C, for the angular adjustment of the figures.
E, E, pinion of any number of teeth fitting on the shaft carrying C and D.
H, H, large wheel of 120 teeth, forming foundation of the second part, and driven from the pinion E by the wheels F, G, and T.
L, large wheel of 96 teeth driven by the wheels and pinions I, J, K, and forming the foundation of the third part, M, which carries the nose of the chuck.
N, N, self-adjusting radius plates for carrying the various change wheels, &c.
O, P, the eccentric slides of the first and second parts.
Q, R, the screws working the eccentric slides.
A PAPER ON THE PRINCIPLES WHICH GOVERN THE FORMATION AND APPLICATION OF ACUTE EDGES, WITH SPECIAL REFERENCE TO FIXED TURNING-TOOLS, CONTRIBUTED BY MR. DODSWORTH HAYDON.
"The formation of the tools used for turning and planing the metals is a subject of very great importance to the practical engineer, and it is indeed only when the mathematical principles upon which such tools act are closely followed by the workman that they produce their best effects."--Holtzapffel, vol. 2, p. 983.
As the best lathe can do no more than place the work in the most favourable position for the operation of the tool, and the best tool can only do good work when _applied_ as well as _constructed_ on true principles, no argument is needed to prove the truth of the statement taken as the text of this paper.
But while many of our most eminent practical authorities, such as Nasmyth, Holtzapffel, Babbage, Prof. Willis, and others, have contributed valuable papers on the subject, no single writer can be said to have embodied all that should be known upon it as a whole.