The rose engine, as hitherto constructed, has not been entirely
supplanted by the neat little apparatus already described, but is
still used almost universally by the watch case makers; and its
construction differs little, if at all, from that described by
Bergeron; although the slide rest used with it is somewhat modified
and improved. There are two kinds of rose engine, in one of which
the mandrel with its poppets and fittings oscillates between centres
fixed beneath the lathe bed; while in the other, the frame carrying
the slide rest is thus movable, the mandrel head remaining stationary
as in an ordinary lathe. In both cases the mandrel is allowed a
to-and-fro or pumping movement in its collars; as the rosettes used
are cut upon the face as well as upon the edge; and the rounded parts
of an article can be operated on as well as the plane surfaces.
The second pattern, in which the poppet remains a fixture, will be
first described, because it is capable of being applied to an ordinary
lathe for surface work, and if the lathe has a traversing mandrel, it
can be completely fitted for rose work.
The drawings and description annexed are from Bergeron's work; but the
slide rest there represented, and arrangement of screwed mandrel, are
omitted as obsolete:--
A strong iron frame, A, A, Figs. 295 A, 295 B, and 296, is made
with one of the ends carried up and branched, so as to embrace the
mandrel and rosette; which latter is attached to the back part of
the chuck which carries the work. The top of the frame is double, so
as to form of itself a lathe bed of small dimensions, upon which an
ordinary slide rest can be fitted. It must, however, be used with a
short socket, or it will be too high; as the top of the frame alluded
to stands slightly above the level of the bearers. B, is a point of
hardened steel which fits into a conical hole in the bottom of the
lathe poppet, or (if this is not long enough to reach a good way down
between the bearers) into a piece of iron arranged for the purpose
similar to that now to be described, and which is again shown in Figs.
297 and 298. This is a kind of poppet in a reversed position, the
clamping nut and screw being above the bed, and the head with centre
screw below. The frame lies, therefore, between the mandrel head and
this reversed poppet, or between two of the latter, and oscillates
upon their centres whenever the projections or depressions of the
rosette compel it to assume such motion.
[Illustration: FIG. 295A.]
[Illustration: FIG. 295B.]
[Illustration: FIG. 296.]
Fig. 299 is a section of the chuck which carries the rosette, the
latter being shown in position. A, is the body of the chuck; B, the
inside screw to fit the mandrel. On the outside of this part are a
few turns of a somewhat finer thread, beyond which a plain part is
left next to the flange, C, and on this the rosette is placed, and is
clamped by the nut, cut outside into beads, or milled, or left plain
and drilled for the insertion of a lever pin; this nut is marked D
in the figure. It will be seen to lie within a recess formed in the
face of the rosette, E. The latter is shown in Fig. 300. A, is the
recess just alluded to; B, C, the pattern on the face and edge; D, the
large hole in its centre, allowing it to be slipped on the back of
the chuck. It is prevented from turning on the latter by a pin, which
fits into the small hole, F. From the front face of the chuck rises
a conical pin, G, similar to that on the eccentric chuck, over which
fits the circular division plate, I, with its projecting screw, H, to
hold the ordinary chucks. This plate is recessed at the back, leaving
a mere ring of metal, _e, e_, which fits a corresponding circular
groove, and secures the steady movement of the plate, which is fixed
by a conical washer and screw, as seen in the plate. This division
plate is formed with cogs, into which a stop falls, as described,
when treating of the eccentric, but the divisions are differently
arranged, the cogs being divided into sets of eight or ten teeth. Let
the whole circumference be first divided into six equal parts, and,
beginning at the first division, cut six or eight teeth, as if the
whole circle were to be divided into 60. Pass to the second portion,
and cut eight teeth, as if the circle were to be divided into 72. Let
the third carry eight teeth, with a pitch of 80 to the circle; the
fourth a similar number, with a pitch of 84; the fifth 96; the sixth
100 to the circle. These must be cut with the same cutter, so that the
spring click, or stop teeth, may fit any of the six sets. There will
be several undivided spaces, which are to be left plain. The several
sets are to be marked in numbers, so that the pitch may be discovered
at a glance, and the teeth in each being so few will hardly require
separate numbering. The part of the apparatus which carries the
rubber--that is to say, the heads of the branched part of the swinging
frame, are made flat on the top, which projects on three sides,
forming small tables on which the actual holder or clamp can be fixed
by a turn of the screw, X, in the first figure. The rubbers are merely
flat pieces of steel, with edges sufficiently sharp to penetrate to
the lowest depths of the undulations and recesses on the rosettes, but
rounded off and polished, so as not to cut and damage the softer metal
against which they act; other materials have been tried, as ivory, and
the harder tusk of the hippopotamus, but hard steel is most generally
preferred. It is, of course, necessary that the rubber press with
some force against the rosette, which force should, moreover, admit
of being regulated at pleasure. This is effected by a spring of steel
under the lathe bed, to the end of which is affixed the arm, W, which
has a ring handle nearest to the operator, and is perforated with a
row of holes from end to end. This arm is flat, and falls into a fork
at the end of the tail piece, Y, which is seen in the second figure
attached to the centre of the lower bar of the frame. A pin passes
through holes in this fork, and through one of those in the arm. By
this arrangement it is easy to regulate the force which the spring
shall exercise, as this will be increased by moving the pin nearer
to the spring, and diminished by placing it in a hole nearer to the
ring handle. In forming the rosettes great care should be exercised
to make the corresponding parts agree. The depth of similar hollows
must be precisely equal, and elevated portions intended to match, must
do so with great accuracy. Supposing, for instance, a rosette to be
made with ten elevations and ten recesses, all of equal curves. If
these are accidentally unequal, and it is desired to arrange a set of
these waved rings one within the other, so that the depressions of
the one shall be opposite to the elevations of the other, or so that
this effect shall take place gradually--if the curves of the pattern
are unequally cut the several portions of the device will not tally,
and an irregularity will be produced of disagreeable appearance; an
inspection showing at once that such irregularity is not part of the
device, but unintentional and erroneous. This leads to a consideration
of the division plate of this rose engine, and an explanation of the
object of its peculiar construction. The pattern of the rosette is,
as it were, in sections; either similar elevations and recesses are
alternately repeated, or there may be a variety of such, extending
over a part of the circumference, and forming a certain complete
device, which may then give place to a second pattern, extending a
similar distance; and these two may alternate regularly round the
circumference. Each of these sections must be of precisely similar
length, and the repetition of the pattern must also be precisely
similar, for the reason stated above.
[Illustration: FIG. 299.]
[Illustration: FIG. 300.]
[Illustration: FIG. 297.]
[Illustration: FIG. 298.]
It is evident that all possible alternations of the device or set
of devices may be obtained by means of six or eight notches of the
division plate; for, by moving it forward to that extent, the whole
pattern may be compassed. In treating of the second form of rose
engine, and of the method of using it, this will again be adverted to,
and illustrated by an example.
Hitherto we have spoken only of the use of the pattern on the edge of
the rosette, but, as already stated, it is frequently repeated on the
face, and by this means it becomes easier to work upon the outside of
a cylindrical piece, as well as on the two ends. Patterns thus cut on
the face of a rosette tend, of course, to move the mandrel to and fro
in its collars, which is only possible when the lathe is made on the
plan of a screw-cutting or traversing mandrel lathe. The spring which
keeps the rubber in contact with the face of the rosette is shown at P.
The head on the top of the arm, which forms the clamp or holder of
the rubber, must be turned round to face the rosette, or a separate
rubber must be used, which passes through the clamp at right angles
to that used in surface work, and the frame must be prevented from
oscillating by a stop which fits between the bearers of the lathe, and
embraces the upright side of the frame. The top of the slide rest must
be turned round, or a side tool used. In this case, the rest and frame
with its rubber become fixtures, as in ordinary turning, the mandrel
and work being alone moved in correspondence with the pattern on the
face of the rosette. It would indeed be much better to do away with
the frame altogether, fixing the rubber to an upright pedestal mounted
on the lathe bed, and using the slide rest in the usual way, were it
not that in general the work is constantly being varied, the side
and face being worked in turn--and the apparatus is rather cumbrous
to remove and re-mount often. It is, nevertheless, easy to finish the
ornamentation of plane surfaces first, and then to remove the frame
altogether, and substitute a fixed rubber, as stated.
The rose engine now described has certain evident advantages over the
rose cutter frame, and is capable of the most exquisite devices. It
may be, perhaps, a mere question of taste, whether rose engine work
finely executed is not in point of beauty, superior to any that can
be done by geometric chucks, however elaborate. That it is so, is
decidedly the writer's opinion, more especially when this apparatus is
used in combination with the oval chuck. Moreover, there is nothing in
the form of rose engine described to make it a very expensive article,
or beyond the skill of an amateur; and with a set of only three
rosettes, the patterns may be varied continually, and multiplied--if
not _ad infinitum_--yet quite sufficiently for the display of skill
and taste of the operator.
In using the rose engine, it is necessary to carry the cord to the
pulley from a very small wheel on the axle. Sometimes the lowest speed
pulley of the flywheel may answer, but if the recesses of the rosette
are deep and sharp, or only slightly rounded, it may become necessary
to mount a still smaller wheel on purpose; else the rubber will jump
over and miss parts of the design, thereby spoiling the work. The
watch-case turners, indeed, altogether dispense with the flywheel, and
use instead a small pulley, fixed to the side of the lathe bed, and
turned by hand.
These artificers always use a more elaborate form of rose engine,
which will be presently described, and which is the most perfect in
detail of all similar contrivances, but it is necessarily costly, and
cannot be said to be well adapted for plain turning also, except in a
limited degree. The work, if not of soft material, like a watch-case,
should be turned first of all upon an ordinary lathe, the mandrel
screw of which is a counterpart to that of the rose engine, and the
latter should merely be used for the final cut, to perfect the form of
the material previous to its ornamentation.
In the Appendix will be found a new method of obtaining the required
oscillatory motion of the rose engine, which might apparently be
applied to tool holder[22] frame here described, or to the poppet head.
[22] _I.e._, the main frame carrying the slide rest.
The rose engine proper is arranged with an oscillating poppet head
carrying the mandrel and its rosettes, the tool being stationary. The
following account of this machine, and the drawings, are copied almost
exactly from Bergeron. The modern rose engine is not indeed made with
the projecting lugs referred to as intended for the application of
the guide ring in oval turning, as this guide is now altered to fit
a poppet head of ordinary form, as already detailed. The pulley and
division plate are also of obsolete form, but as the main arrangement
of parts described are sufficiently similar to that now followed,
Bergeron's drawing and description have been retained. Fig. 302 is
a longitudinal view, and Fig. 303 a transverse view of the working
parts of this lathe. A, A are the poppets, which are in one casting,
with the connecting piece shown by the dotted lines, which latter
has a tail piece firmly attached to its centre, to which a spring
is affixed as in the lathe previously described. In the drawing the
cylindrical collars carrying the mandrel are split, so that in case
of wear they can be tightened in the usual manner by a screw at the
top of the poppet marked B, 303. The lugs, _f, f_, with square holes
_e, e_, are for the application of the guide for oval turning, the
latter being originally a ring with slotted arms on either side. The
points of oscillation are precisely similar to those of the rose
engine first described, two short poppets C, Figs. 302 and 303, having
centre screws, whose points fall into conical holes made in opposite
faces of the poppet, a little below the level of the lathe bed. These
are formed with a slit to receive the stop _h_, which is hinged at
the point _o_, and which, when raised by a wedge, catches into a
small projection _p_, thereby fixing the poppet in a perpendicular
position and preventing its oscillation. The rose engine can then be
used as an ordinary lathe, to finish the preparation of the work to be
operated on, which should, if possible, be commenced and mainly formed
on an ordinary lathe, the mandrel of which is a counterpart of that
of the rose engine. The tail piece, E, does not require a separate
description, being precisely similar to that already described. The
to-and-fro movement of the mandrel caused by the action of the
rubbers on the face of rosette, is also arranged in a manner similar
to the last. F is the spring, turning in the middle of its length
on a pin in a piece of iron fixed on the bed, so that if both ends
wore free it could swing backwards and forwards between the cheeks
of the lathe on this pin as a centre. The upper end of this spring
is branched in a semicircular form to embrace the mandrel, this fork
falling into a groove formed to receive it. It can thus be brought to
bear against either of the shoulders visible at this part. The lower
end of the spring fits into a notch, or rather a slot in the arm H
of the second figure; the handle of this arm being L in both figs.
This piece is pivotted at K, and at its other end falls into one of
the notches in the retaining plate, G, of the first figure. By this
plan the tension of the spring, can be brought against the mandrel in
either direction at pleasure, for if the lever is placed in one of
the left hand notches, the tendency of the spring will be to move the
mandrel towards the right, and _vice versa_. The tension of the spring
can also be regulated by the use of the groove B or X at pleasure. In
the second figure of Bergeron's the piece which at first sight appears
to be a continuation of the holding down bolt of the short poppet
carrying the centre screw, is the tail piece or lower end of the long
spring just described, and its reduced extremity is visible passing
through a short slot in the lever H, near the handle of which appears
the _edge_ of the notched piece G of the other figure. All the above
parts are commonly of iron, the following are in brass or gun metal.
[Illustration: FIG. 303.]
[Illustration: FIG. 304.]
[Illustration: FIG. 302.]
On the bed and parallel to it, two pieces of brass, or standards,
rise, similar to H in the first figure, the two being opposite to each
other, one on each side of the mandrel, as shown in the second figure.
Both these are firmly secured to the bed by long bolts and nuts, it
being of the utmost importance that they should not move or vibrate in
the least. They are in addition united to each other by two horizontal
braces, one of which is seen at N in the second figure. At _l, l_
are seen two rectangular notches, which are the ends of grooves made
in the upper part of the head piece, H, and which traverse its whole
length. They receive the crooked part, _a_, of the rubber holder,
Fig. 304, so that the latter can be slid along this bar, and brought
opposite to any one of the rosettes, after which it can be secured in
position by the screw, _b_, Fig. 304. The mandrel is thus arranged.
It is cylindrical, with a shoulder against which the chucks can rest,
as in an ordinary traversing mandrel, and a similar but reversed
shoulder at _g_, Fig. 302. Against the latter abuts the end of an
accurately turned sleeve of brass, which fits over the mandrel with
slight friction, so as to have no shake or play upon it. Upon this
sleeve the rosettes are placed. They fit accurately over it, and are
prevented from turning round upon it by a feather extending the length
of the sleeve, which fits into a corresponding notch cut on the inside
of the rosettes. These are arranged in pairs back to back, and each
couple is separated from the next by a short sleeve or ferrule, which
Bergeron recommends to be of wood, as tending to hold the rosettes
more securely than metal when pressed together by the nut at the end
of the set. The fibres of the wood are to be placed parallel with the
mandrel, because there is no shrinkage of this substance as regards
its length. The pulley is fixed beyond the rosettes on a part of the
mandrel filed into six faces for that purpose, and lastly comes the
nut, which secures all the parts to their several positions, but which
nevertheless does not so jam them together but that the mandrel can be
turned within the sleeve when the positions of the rosettes are to be
changed in the course of working a pattern. The division plate is not
attached to the pulley, though lying close upon its surface. It slips
on to the sleeve on which the rosettes fit, and its spring-catch only
on the face of the pulley. Thus the latter is held to the sleeve and
its fittings when the catch is down, so that all turn together, but,
when the catch is raised, the division plate, carrying with it the
rosettes, can be turned round upon the mandrel as may be required. It
is not necessary to repeat what has been said respecting the manner
of graduating the division plate, as that used with the lathe already
described is in that respect a counterpart of what is used with the
rose engine now treated of.
[Illustration: FIG. 305, 306.]
[Illustration: FIG. 307.]
The following description of the method pursued in turning a pattern
shown in Fig. 307 will suffice to show the working of the rose
engine:--First, says Bergeron:--It is not enough to know the general
construction of the rose engine, it is necessary to know thoroughly
the particular one in use, _i. e._, as regards the details of its
construction, the slight defects or imperfections it may chance to
have, and the means whereby they may be lessened or corrected. It is
necessary, in addition, to know well, and to have always at hand, the
numbers of each rosette, or any rate to have a table of them which
can be readily referred to. It is equally necessary to recognise at
a glance the various sets of divisions on the division plate, for
which purpose, and that no mistake may be made, such numbers ought
to be engraved upon each. The same holds good with regard to the
slide rest, and, in addition, practice should be frequent upon box or
other inexpensive material by which the turner may have made himself
perfect in the several combinations possible, and the various effects
producible by the rosettes and different shaped tools over which he
has control. It is thus, by actual experiment only, that the turner
can become acquainted with the powers of his own lathe and apparatus,
and thus only, after working out the patterns already executed, will
he be in a position to design new ones, and to work with ease and
certainty. The rose engines are usually fitted with tools of variously
shaped edges, as shown in Figs. 305 and 306, by this means a pattern
of some width and great variety is of course produced at once, and
by one rosette. In the following, however, a tool with single point,
Fig. 308, is to be used. This simplest design is supposed to be on
the cover of a box or other plane surface, and it is evident that
the movement or oscillation required of the mandrel is that at right
angles to the bed of the lathe. To obtain this movement, when the
rubber is fixed in its clamp, on the side of the workman, as it is
necessary that the rubber should press against the rosette through the
medium of the spring, the handle of the lever, Fig. 302, must be drawn
forward towards the operator, and kept by a pin, as described, passing
through it and the tail piece of the mandrel frame. The tension must
not be too great, especially if the rosette to be used is deeply
indented, and care must be taken to free the frame from the action of
the stop, _p_, by removing its wedge before making any attempt to try
the pressure by moving the mandrel. The design under consideration is
produced from rosette numbered 2 in the drawing, and in fixing the
rubber care must be taken that it does not bear against the adjacent
rosette. Choose a rosette of forty-eight teeth or undulations, and
as the second circle of ornamentation exactly intersects the first,
the raised part of the one falling under the depression of the other,
and as it were _halving_ it, the set of divisions on the click plate
to be used will be twice 48, or 96. Place the rest parallel to the
face of the work and so that the forward motion of the tool shall be
perpendicular to it. By means of the leading screw of the rest, place
the tool near the edge of the work and level with the centre, and
gently moving it forward and putting the lathe in motion, commence
the cut. After having made a light cut, without moving the tool, stop
the lathe and judge of the depth of cut, and if sufficient, screw up
the stop screw of the slide rest, to insure all the following cuts
penetrating to the same depth. Observe the position of the tool as
marked by the graduations of the slide rest, and then withdrawing
it from the cut, move the click plate one notch, which will divide
exactly in half the several undulations of the rosette. By the rest
screw move the tool towards the centre of the work and mark the
number of divisions passed over, so that the circles of undulations
may be equidistant, and cut a second. Now for the third, _go back or
advance_ on the click plate one division, for the position of the
undulations in the third is precisely that of the first circle. It is
indeed immaterial whether an advance or retreat of one notch is made
in this case, but now is evident the reason for not dividing the plate
equally all round, five or six teeth being ample for each division. If
there are eight rosettes the plate should be first divided into eight
parts, and each rosette having a different number of undulations,
these eight parts should be divided into degrees proportionate to
the numbers on the rosette, the one being a multiple of the other.
In working the _side_ of a cylinder, that of a box, for example, the
longitudinal movement of the mandrel is required, the poppet being
retained immovable by the wedge and stop. The tool is to be placed at
right angles to the side of the work, the rubber brought to bear on
the face of the rosette. The method of working will be self-evident,
after the description already given. It is impossible in a brief work
like the present, to go into details of other patterns referred to and
illustrated by Bergeron, one or two of which are nevertheless of great
beauty, and are executed with the aid of the eccentric chuck mounted
on the mandrel of the rose engine. There is, however, a different
class of work, to which reference will be made in our next, and we
shall also give a description of a simple addition to the slide rest,
used by watch case turners, which does away with the necessity of
counting the number of divisions upon this instrument when used as
above.
The slide rest used by the watch case turners is almost identical
in form with one figured and described by Bergeron. It is necessary
that the tool holder should have a circular motion, somewhat similar
to that of a spherical rest, in order to reach the sides and curved
surfaces of the articles to be engine turned; hence the tool
receptacle and its bed work upon a central pin. The pin here called
"the bed" is usually a flat brass plate of a quadrant form, the
central pin being at the apex, and carrying on its face the guides for
the tool receptacle. The pin on which it turns is a reversed truncated
cone rising from a similar flat plate, which itself forms the sole
of the rest, or traverses the lower frame as usual; when the tool is
beyond the central pin, it will ornament conical surfaces, and _vice
versa_. On the edge of the arc is a racked part, and a tangent screw
works into it. The tool is moved to and fro by a lever, as usual, the
depth of cut being regulated by a stop screw. These details being
already entered into, in treating of slide rests and chucks, need not
be more specially explained here; but a contrivance for regulating the
traverse of the upper part upon the frame underneath, is ingenious and
serviceable, and will therefore be described. The end of the leading
screw is fitted with a ratchet wheel of the same construction as
that of the ratchet brace for drilling, patented by Fenn, of Newgate
Street, to which in the same way a handle and spring are attached,
as shown in the drawing, Fig. 309, A, and Fig. 310. The handle rises
between two semicircular plates drilled in the face, with holes for
the reception of stop pins, B, C. These regulate the traverse of
the handle, and thence of the screw. If the former, therefore, is
thrown over till the left stop is touched, and then pulled forward to
the other stop, between each cut of the tool, the latter will leave
equidistant spaces upon the work, without need of counting divisions
at each cut. As a traverse of one inch or more of the lever handle
at the place of the stop pins only moves the screw a very minute
quantity, the holes for the pins need not be very close together even
for fine work. This is a very simple contrivance, and perfect in
action, enabling the operator to work with ease and certainty, and
with great speed.
[Illustration: FIG. 309.]
[Illustration: FIG. 310.]