ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1864.

MAY 15, 1891.

minutes running at this speed, again take out
collar and spindle, and wipe clean from all
oil and dirt, repeat the operation, using this
time watchmakers' polishing rouge. After the
necks are quite polished, for the last time take
out, wipe clean, wash in oil or paraffin, dry, and
wipe clean; remount again, using now good
neat's-foot oil only. There now only remain
the lever and handle jj and the link k. The
lever j is in the original of hammered gun-metal,
as is also link k.
out of the solid and carries the joint-pin, as
shown. The hub or boss working on the fixed
stud n need not of necessity be turned, but it
The fork end of lever is cut
looks better if so treated. The whole apparatus
(former excepted) is now complete and ready for
action, and now consists of two elements-one,
with a radius equal, in this case, to the distance
from centre of post to centre of spindle in.
the swing cutter-head, having a segmental swing

pair marked, as also entrance hole in hub and through collar and tail-pin holes, from middle and spindle. The necks must now be accurately front of heads, into the two holes a3, a3, fitted to collars, run the chuck holding collar on mentioned previously; file off burr, oil both mandrel, and "readle" the conical-broached or collar and tail-pin, insert in place; with a spindle bored hole or neck; then with one end of spindle also, screw up to proper bearing, and tighten up (the tail end), supported by poppet-head centre, binding-screws, when the headstock may be enter the other or upper part into collar and try considered finished. It will be seen that by the for taper: the writer at this stage of the work above method of construction the spindle can be transferred the spindles, to finish, to a clock-readily removed at any time, either for cleaning, maker's bow turn (this tool is generally held changing, or altering height of cutter centres. We in the vice), as for small work it is preferable to yet have to finish the base or slide b: before pera treadle-lathe, as both speed and cut can be manently screwing in centre post b', we must better felt and regulated. Leave the necks of drill, tap, and countersink the hole and seat for spindles so that the butting shoulder does not the conical-seated fixed stud N, and to turn, quite bear on collar, as this will be effected when thread, or screw and fit the latter, as shown in grinding-in and finally polishing. We now have Figs. 1, 2, 3, and 4, after which the hole at front to finish off the collar, which was purposely left and of slide is to be bored and tapped to receive in the chuck. At its thickest part it will be (as the open loop or hook for the rubber spring s: it was turned down from ) about in. diameter; this may, be of brass, gun-metal, or iron. The leave a shoulder or collar of this about in. deep, post b' may now be screwed in hard to the slide finish the lower end of collar, and cut off just b, and the entire slide and swing head will be radius of cutter, which, however, is variable; beyond above-mentioned collar or shoulder, after finished, with the exception of the hardening of while, secondly, the entire cutter-head and slide having either filed or milled thereon two flats to the collar and two spindles. We now come to has a sliding motion square to lathe-bed, and the suit a spanner. The other, or top, end of collar the most essential and important part of the combination of these two movements will follow may be finished off either on a mandrel'or by apparatus screwing it into a boxwood chuck, recessing, of holder (the method of setting out the curves of In addition, the whole apparatus may be moved course, an oil-cap on top. On the body of the the latter will be treated further on): by inspect- to any part of lathe-bed. The swing action is namely, the bridge and former any curve cut on a former fixed on the bridge. swivelling headstock there is a boss to receive ing the drawings, it will be seen that the bridge given and regulated by the lever handle a', or by the screwed stem of the lever handle a'; this boss qq is a gun-metal casting, resting on and fixed an indiarubber-band spring looped over the end should be drilled right through into centre post- to the lathe saddle in the manner shown in Figs. knob of lever handle while, the other end of said hole, and finished with a plug top, also 1, 2, and 3. It is best seen in Figs. 1, and 3. band-spring is attached to any fixed point on countersunk to receive the conical seat of handle It will be noticed that one side, the left, is lathe-bed, headstock, or poppet-head to the stem a' shown in Figs. 1, 2, 3, and 4, the thicker than the other, and to it are fitted the right wooden or, better, vulcanite handle for which vertical guide strip running against left side required; while the slide can be turned and driven on to taper stem at a of saddle, and the permanent stud pivot 1, on by-1st, the lever j and link k pivoting on the or left of future period. We next have to file the seat for which works the link kk, which is drilled fixed studs n and 7; 2nd, by the action of a stout apparatus as may be the guide-pulley standard; this should be done with five change holes to work on b is actuated carefully, so that the seat or bed be truly parallel pivot or and square to axis of headstock. The standard on the centre of its highest part provided with a motion lever as shown. When the swing action stud l. same rubber spring band s, attached to hook on slide b, may be either of iron, brass, gun-metal, or mal. guide-seat, on which are clamped the various is not required, as for wheel-cutting, drill The bridge 97 is also the other end being looped over the sliding cast iron. The original is of gun-metal, well formers in the manner shown in the drawings. fluting, or serrating, the swing-head can be hammered to stiffen it; the hole for guide- The bridge is adjusted and held in position by locked fast, by the contrivance shown in Fig. 5, pulley axis must be bored to be truly square with the two screws at either side, tapped into body and by means of the cam lever m, which is axis of centre post, and the standard fixed to of saddle on the left side and into the V strip pivoted on a screw tapped into body of slide 6, body by two in. screws, and when accurately on the other, passing through the necessary slots and held in position locked, or free, by a screw in position, two small holes for steady pins are in the wings of bridge. The screws are provided and lever also tapped into body of b, and working drilled right through standard, and about in. with tolerably stiff washers. We now come to through an arc slot in cam_m. into body of headstock, and two steady-pins the last item in the construction of the apparatus: front segmental face, has a V notch, which, when fitted in. Of course, the guide-pulleys must the hardening of collar and spindles. The writer locked, engages the tail-pin o', and thus holds be exactly of the bottom of gorge same diameter, at the has found, from experience, that mild steel, which the swing-head immovable. Supposing a former The cam, on its more especially, and the of itself is almost as stiff as cast steel, has the of any shape or width, within the scope of the axis must be provided at each end with washers property, no doubt from its purity, of taking apparatus, to be firmly fixed into the former and keeper pins. We left the centre post driven case-hardening remarkably well-better, indeed, guide-bed on bridge 7, and the swing-head into the headstock for the purpose of finishing than ordinary good iron, or even best stub, gun, locked, the action of the spring bands will at the latter, so after facing and finishing off the or dented irons-and on account of this property once bring the tail pin in contact with and ends of headstock, it may be driven out, reset the writer has, for such purposes as spindles, butting against whatever part of the curve of between lathe centres, about one-third of its collars, mandrels, and for most round work or outline of former is in line with it, which, in length in the middle turned down, say, 32, so as hitherto made of steel, but where no cutting edge the drawings, is the extreme point of curve to leave bearings at either end only. These two is required, adopted almost entirely the new metal. representing the outside or diametral point of a cylindrical bearings are then to be carefully It is, as before mentioned, very stiff; it is much gear cutter, or the bottom of a wheel-tooth space. reduced, so as to require (only a little grinding softer to work, and by cementing, say, a in. If now a prepared cutter blank be driven on, or in to headstock to make a perfect sliding fit spindle in a closed clay muffle or a piece of gas- otherwise held on a mandrel, and set, having without shake. Over the top of post a steel, iron, piping, simply packed round with powdered a carrier fixed, between lathe-centres, whator gunmetal washer is to be fitted tight, about prussiate of potash two-thirds, and charred ever in. thick. This is driven on so as to be flush leather or with top end of post. Now, with a fine centre- luted and covered, and exposed in a bright, extreme diameter of cutter ether animal charcoal one-third, will punch, and at the junction of the post and clear cinder or charcoal fire for from 15 to 20 action of the band spring S, or by the lever j, cutter may be on the washer, make a centre dot, and with a tin. minutes, will give a coating of cemented steel with a pressure equal to the pull of the spring, be brought into cutter spindle contact with the lrill, drill a hole which shall be half in washer of quite in. thickness-quite sufficient for all minus friction of slide b. blank by the and half in centre post and parallel to axis, practical purposes, and to allow for grinding. of serrations to complete cutter blank having been into which is to be fitted tight a wire key. The article when quenched in quite cold water determined by a sketch, and the index set to O This is merely to prevent any action of will be of a uniform dull grey, and will resist all on division plate, put on the gut from overhead The requisite number the headstock revolving the washer, and but the best saw files, in fact it is quite equal to drum over guide pulleys and spindle pulley, make thereby, chancing, to slacken the screw b", which steel drawn to straw temper; it is also so tough a tentative cut for depth, but rather less than holds the headstock in its place; the washer is that the articles, after hardening, may be set full depth, move division-plate requisite number then turned down to thick; it remains to drill between centres, or on a lead block, and trued of holes, and make another cut (the swing-head up the top centre hole in post a little larger, say with a zinc hammer without the slightest fear being locked the while). Now with a magnifier 32-, tap it with a rather fine pitched thread of breakage, or of having a waster. (screw-plate threads are most suitable), and fit advantage is that in the hardening, the mild steel cuts; if about do of an inch shows uncut, the a cheese-headed screw, a good fit; the head may warps or distorts much less than does steel. Another examine the edge of cutter left between the two be finished with holes for tommy, or with kerf course before putting into the case or muffle, to ing former p must now be set forward so that the for screw-driver. their places in the headstock the collar a', and attached a piece of stout binding wire as a loop, when it is firmly clamped by the two screws on We next come to the fixing in whatever object is to be cemented must be extreme point of former buts against tail-pin O', Of depth will be about right. The bridge a carrythe tail-pin O'. The collar hole having been whereby to withdraw it quickly and quench. The wings. Now unlock the cam lever m, so that tapped with the special tap, as described, the spindles and collar being hardened and trued, the cutter-head is free to follow the contour of tail-pin hole is next tapped in a somewhat may now be put in place for final grinding and former, and make a complete cut on one side of similar manner by making a long 3in. special polishing. In this case, as the surfaces are very blank, keeping the tail guide pin well in contact steel wire tap, and fitting into collar hole a turned hard, a little washed emery and oil may be used, till the pin rests in one of the hollows of the and bored temporary boxwood collar, the tap and the spindle rotated either by its own former, when further action of milling-cutter fitting and running in hole; by this method we pulley, or by pinching a carrier on the pulley will stop. The action is repeated all round one insure the screwing or tapping being true and in end, and feeding up with tail-pin. When the side of blank. In cutting, do not crowd or force line. It now only remains to drill the holes for necks and stop shoulders have been ground to a the cut, but handle leverj gently. the binding-screws, as shown in section at outer fair bearing, take collar and spindle out and always lubricates cutter with oil in preference to ends of collar and tail-pin heads, first with a thoroughly remove, as drill half-way through for body of screw, then frequent oil cleaning, all traces of emery, put the writer cuts one side, the right, only at first, The writer with a for tapping hole, tap and finish with together again, and this time use purple crocus is because milling-cutters generally run from as possible, by soap-and-water for this work. tap right through tap-hole, and fit two and oil for polishing, running the spindle now left to right, and in cutting The reason why screws, with capstan heads, these fitted by pulley, and at a moderately quick speed, say side of n out, with a sharp hack-saw, cut right 500 to 600 revolutions per minute. After about ten has a tendency to override blank, the mill, the left-hand when in cut, or to cut too

far

a

greedily, which would show bad work, and this a piece of fin. iron plate, having a handle riveted tendency has to be controlled by firmly handling to it; this, with the cutter on it, bright side up, the lever, and the spring s may in this case be is now held over a gas or a spirit flame, till a full unhooked. It is of the utmost importance in straw colour shows on the bright cutter, when it cutting such small work that there shall be no is at once tilted into cold water. If the steel shake or backlash between the carrier and catch used happens to be of extra fine quality, the or driving plate, or bad work will be the result, temper may be drawn to deep straw colour. The and perhaps a damaged cutter; and, therefore, form of cutter the writer mostly uses is shown at the writer strongly recommends for this kind of Figs. 9 and 10. As before stated, the serrated work, and also for screw-cutting, the form of cutters cannot well be sharpened, because no carrier shown in Fig. 2, which is made to grip emery wheel got up to such a sharp angle would firmly the driving stud on catch plate. The stand more than two or three teeth sharpening. hardening of these cutters requires care, and the In order, therefore, to obtain a cutter that can writer adopts the following method: Prepare a be sharpened, till the cutting teeth will no 3-wire stem of twisted wire (like a common longer stand the strain, but which will, in toasting-fork, but smaller wire), about 6in. or the long run, last quite as long, or longer, Sin. long, turn out equally at right angles to an ordinary serrated one, the writer, after stem about in. of the ends. The top of stem turning up the cutter blank to fit and must be small enough to pass through eye or shape, proceeds to drill round the body of centre hole of cutter; procure a small 131b. to blank, and just within and clear of the cutting 21b. crucible, in which drop some fine sand, portion, a series of eight, nine, or ten holes, about lin. deep; place this in a strong, clear quite through; he then cuts, with an angular cinder or charcoal fire, drop the cutter over stem cutter, the spaces, as shown in Figs. 9 and 10, of wire holder, when it will rest on the three afterwards backing off a portion of the teeth by bottom prongs; place this in crucible, resting on hand, although this could also be done by cutter the sand at bottom, and cover over cutter with in one operation by properly shaping the mill a few small pieces of charcoal, to partially exclude b', Fig. 9, in which fig. the process of cutting is air. When the steel is at the proper heat (which shown, while in Fig. 10 the grinding operation is will depend on the quality of the steel), say a depicted. It is to be noted that, in making full cherry-red, lift the wire stem and cutter out all cutters, a division plate or wheel is absoof crucible, and immerse quickly in a pail, or lutely necessary. Of course, the above-described large basinful, of cold water, moving stem and cutters have no clearance, i.e., the un-cut cutter, vertically, up and down in water till quite portion of each tooth, following the cutting edge, cold. One face of cutter is then brightened with remains in slight contact with the work operated an emery stick, wiped quite clean, and laid on lon; but they, nevertheless, cut remarkably well.

In order to toughen the bodies of these cutters, which the drilled holes somewhat weakened, the writer, after having hardened and tempered them, further lowered the temper of the body or centre, without in the least lowering the temper of the cutting portion of teeth, by the very simple operation of cutting through a raw potato a through hole about the diameter of cutter at pitch-line, forcing the cutter into this hole, so that the teeth are quite bedded in, and then inserting into eye or centre hole of cutter a taper iron rod a little smaller than hole, heated to a bright red; the hot iron soon lowers the temper round the eye from brown, vanishing outwards to colour of original temper, as the cold mass of potato prevents the imbedded teeth rising in temperature higher than boiling point, 212°. On withdrawing the rod, of course, all lowering or softening action ceases, and the cutter is very materially toughened. It is a well-known fact to those who have to do much steel-hardening, that sharp nicks or grooves give rise to "water cracks," which, although they may not be visible, except on very close inspection with a magnifier, will show plainly if the tool breaks, as it mostly does, at such a crack or flaw, and on two occasions this has happened in the writer's experience with finely serrated cutters, bought at one of our noted tool warehouses. By far the best, and, indeed, the only perfect, form of cutter at present known are those made by the celebrated American firm of Brown and Sharp, shown in Fig. 14, in which, although the shape of the teeth may not be exactly correct, the principle on which they ar

=

The outlines can now be filled in and the metal cut to the shape; the two circular plates of in. radius being also removed. The thick lined circles are not to be taken any notice of at present: they represent the positions of the diaphragm covers" and "bearing collar."

18.-Diaphragm Covers.

One of these is shown in section and in plan at Fig. 22. They are in. thick, and are bored at first with a hole in. diam. Into this hole a short length of in. round brass rod, turned down at one end a to fit into it, is sweated. A fin. hole is then run through the rod, and afterwards coned out at the upper end, as shown, to a diameter of in. The underside of the cover is slightly turned out (b) to permit of the vibrations of the diaphragm, a small, flat annular space c being left, 1in. inside diameter, to take the rubber rings which clamp the diaphragm in place. The larger annular projection d is to take eight in. screws, placed evenly, as seen in e.

made is correctly given. It will be observed, The writer has been carried away by his subject describe the arcs fg. With centre x and radius by examining the drawing, that the shape or beyond the usual limits, and must, therefore, in., describe arc h. From the arch to the contour of cutter is not turned in the general postpone his intended observations on the arcs fg, draw two tangents, j k. A line, 7, acceptance of the term, as are the blanks for "Vertical Slide and its Uses" till his next parallel to the chord z, and at a distance of ordinary cutters, but each separate tooth has its article. He will, for the present, give a short 2in. from the point x, must now be drawn. own individual centre eccentric to the live or description of the two planing motions, which, Two lines, mn, are drawn from centre x through running centre. By this method of construction of course, are to be used separately, shown in the centres bc. On these lines at 3in. from a cutter is obtained which can not only be ground drawings Figs. 1, 2, 3, and 4. The apparatus, draw two perpendicular lines, p. These or sharpened till too weak to do more work, but consists of a saddle, ccc, sliding on lathe-bed, lines being in. long, and divided equally by the clearance is positively perfect, the portions but to which it can be firmly clamped at any the lines mn, the line I will then meet these short of teeth immediately behind the cutting faces, desired point, regulated only by the length lines at a r. Tangents st to the arcs fg are owing to their eccentricity, never touching the of the connecting-rods ff, of which the drawn meeting at the points u v; these points work. The writer believes that only one firm writer has two of different lengths, or by being already found. in England has license to make these cutters, the link i i. The saddle carries (cast with it) which are patented. In sharpening these cutters, two vertical horns connected at the top by a plateaccurate division is a positive necessity. Figs. 6 iron cross stay, and furnished with facing bosses', and 7 show the mode of obtaining the scale for through which run the two spindles e and d', diametral or (so-called) "Manchester pitch" which can easily be removed by simply taking wheels. Fig. 6 represents an 18 p. wheel, or out the keeper pins at back ends of spindles, and one having 18 teeth on a pitch line lin. diameter. releasing the pin connecting rod with saddle. Here the lin. diameter divided into 18 parts The hand motion is from the top spindle, fitted + two such parts gives the size of blank for with a flywheel at back, on which is percutting; 60 that for any blank, say for manently keyed a pinion, e, of 20 teeth 18 p., 45-toothed wheel, the diameter will be, by con- gearing into a plate-wheel of 85 teeth, keyed structed scale, 45 divisions + 2, or by measure fast on axis of spindle, d'. On the inside of 24in.in. nearly 2in. The above opera- this wheel are cast four small facings to corretion is shown in Fig. 7. Here is a lin. wheel spond with the four crank-pin holes ff' shown 14 p., or a wheel having 14 teeth on a pitch line on plate or disc-wheel, so as to be able to vary diameter of lin.; and here is also shown an the length of stroke This is a much easier 18-toothed wheel of the same pitch, and con- and quicker mode of construction than a slot structed on the given scale. The writer proposes disc, and quite as effective; it can, moreover, shortly to publish, for the use of wheel-cutters be made in a narrower space, which in this and machinists-but more especially for amateurs case was necessary. It will be observed that and readers of the "E. M."a table of scales or the centre d' of wheel d is higher than the pivot sizes of blanks for wheels of all pitches (diametral) centre, f", on lathe saddle. The effect of this from 12 p. to 40 p., from 12 teeth to 150, and arrangement is to give a slightly quicker in stroke also a division-plate table, printed on Bristol than out, or cut stroke. On the saddle c, c, c, is board and varnished. The form of cutter-blanks also cast the horizontal horn projecting over for these pitches is also shown in section, the back of lathe-bed, to receive the fulcrum stud h; inner line on tooth of each showing the depth of in this horn are drilled and tapped a series of serration, and this is the line or curve from which 5 holes, all to fit the stud h. On the stud h is to construct a former p., not the outside or pivoted the lever ', terminating in handle, h". tooth curve. Fig. 13 shows the method of This lever is also bored, but not tapped, with tracing a former. It is to be noted beforehand a series of five holes, besides the one for stud h, that the radius of the mill employed in serrating to receive the fixed stud r fast in the link i, said a blank must not be greater than the radius of stud being fitted with washer and keeper, as is any portion of the curve required on the blank, also stud n; the stud i, on gib of saddle, is perand this must be ascertained by actual trial by manently screwed in, but can be removed if spring dividers before commencing work. The required, although not at all in the way for suitable number of serrations must also be deter-every-day work. Planing or shaping work done mined by a working sketch, as the number of cuts on the lathe must necessarily be short, on account depends also on the angle of the mills in stock: of the spring which occurs on work held between thus, an acute-angled mill would require more cuts centres, and it is for this reason the writer has round a blank than an obtuser-angled one. The made the stroke so short. As a guide and slidingradius of smallest curve, say in., having been rest for the hand-lever h', a raised bed on found, a mill fin. dia. may be selected. This, saddle cc, bounded by the stop c", and the horn of course, cannot have a larger centre-hole c, is provided, and this is filed up tolerably true than in., and that size will fit the smaller of and smooth. As that part of the saddle between the two cutter spindles before described. When the series of holes h does not bear on lathe bed fixed on spindle with its proper numbered washer, (to save work) the raised guide bed and stop if required, mount in swing head by passing would be unsupported, and might spring; to through collar hole, screwing in collar to follow; prevent this, the screw z is inserted, as shown, tighten binding-screw at top (the tail or guide and is turned by the screwdriver, so as just to pin need never be moved, except for taking up take a bearing on lathe bed. In connection with wear or adjusting centre of cutters), and the head the planing and shaping motion, is a properly is ready for work. But to proceed with tracing devised, reversible pawl and ratchet-wheel, the former. With spring pencil bow and carrying on its axis a worm, gearing into a wheel radius equal to mill, describe, in contact with running on a fixed stud, and gearing into another inner line of tooth and beginning with extreme wheel shipped, as a change wheel, on tail end of point of cutter, a series of circles, pricking centres mandrel, the whole taking the place of the ordiwell, in close proximity all along inner contour; nary radial arm; this will also be described in a then with radius of tail or guide pin O', describe future article. another series of circles from the above-mentioned

centres, when a line, tangential to these last circles, will give the outline or contour of former. The two terminal or stop hollows are not absolutely requisite, and the curve or remaining surface of former may resolve itself into a straight line at right angles to axis of former. In the coarser diametral pitches, above 18 p. it is not advisable to use a lin. wheel as the patterntooth for cutters. In the 14 p., as shown, a cutter made to this sized wheel would cut the teeth too pointed. The 18-teeth 14in. wheel,

Since writing the above, Mr. C. Churchill, of Cross-street, Finsbury, has kindly forwarded to me some of the American cutters alluded to, and of which I will give a correct drawing in my next.

HOW TO CONSTRUCT A

PHONOGRAPH.*-IV.
By W. GILLETT.
17.-Spectacle Frame.

M.

same pitch, gives a better form, but a 20-toothed T inspection of Fig. 21. It is cut from brass
HE method of laying this out can be seen by
would give a still better. To those of our
readers who have many wheels of various pitches in. thick. It may be drawn on paper which is
to cut, the writer would recommend to procure afterwards fastened to the brass, or it may be
a Manchester pitch-gauge. It is a brass disc marked off directly on the metal. Take any
about 3 in. or 4in. diameter, on the periphery of point as a in the figure (sufficiently removed
which are cut a few teeth, as of a wheel, of each from the edge of the metal to allow the required
pitch from, generally, 12 p. 36 p., in all from size of frame), and with
a radius of in..
nine to ten varieties. Formers should be made describe a half-circle, a. On this arc, mark off
of steel, hardened and tempered purple; but for two points, be, the chord joining these two
a single job, hard, rolled brass will do. For points being 2in. in length. With these two
cutting thin wheels, such as clock wheels, up to points as centres, and with a radius of in.,
n. thick with the new attachment, the swing of describe the circles de. With the same two
head is quite sufficient for traverse, as the points as centres, but with a radius of lin.,
A sine of such a small arc is not appreciable.

All rights reserved.

The spectacle-frame must now have circular recesses cut out, into which the diaphragm covers accurately fit, and these recesses are, of course, concentric with the 14in. holes already cut therein. The recesses are about in. deep, and receive the diaphragm covers, as shown in section at Fig. 23. The position of the screws with relation to the spectacle-frame is seen by a glance at Fig. 21, being placed in this position to admit the fastening of the stylus guides underneath the frame.

19.-Bearing Collar.

This is merely a short piece of round brass rod in. diam., turned down to size and shape of A, Fig. 23. The bottom part, it will be observed, has a thread cut on it, which fits into a similar threaded hole in the spectacle frame, the centre of this hole being the point x in Fig. 21. In addition to being screwed into the frame, it has circular washer a, in. thick, screwed on it against the under-side of the frame. The washer and the end of the collar must be eventually nicely surfaced off quite square with the axis of the hole; but this, of course, must be left until the final screwing together; but the hole itself must now be looked to, to see that it fits truly on the bearing-post, Fig. 17, p. 133.

20.-Styluses and Guides. These are one of the most important parts of the phonograph, and, therefore, every care should be taken with them. from steel rod in. diam. They are made recording stylus, and c that of the reproducing. Fig. 236 shows the The recording stylus is shaped in such a manner, that a sharp gouged edge meets the advancing sides parallel with one another for about kin wax; the said edge being about in. wide, and the from the cutting edge. This stylus is seen at d and e, being the front and side views somewhat enlarged. The stylus is represented in the drawing as being fastened to the diaphragm by a small nut, which is screwed on the turned. down part of the stylus which passes through a hole in the diaphragm. A much simpler method, and one which does not necessitate the diaphragm being pierced, is to face the top of the stylus rod off quite square, and fasten it to the diaphragm by means of shellac.

wide and 2in. long, having at the centre a fin. The guides consist of a piece of in. brassia. of in. brass rod. This is screwed by means of a

screw at each end to the under-side of the spectacle frame, as seen in Fig. 23 at f f. It is with the centre of the hole in the spectacle frame, now drilled with a hole which exactly coincides and this hole must fit very accurately the cylin drical part of the stylus.

at g; h showing the end of the same stylus rather The reproducing stylus, with its guide, is seen enlarged. It is ground to a small spherical end, the diameter of which is slightly less than the width of the edge of the recording stylus. It is perhaps, needless to say that the surface of this

small knob should be highly polished, and this former having a very keen edge. The guide
remark also applies to the portion of both styluses should be turned down somewhat, as in the figure,
which pass through the hole. so that the smallest to give it a better appearance.
amount of force will move them. The edge of
the cutting stylus, and, in fact, the spherical
knob as well, must be as hard as possible, the

which there are two. They are of in. brass, and are bent at a slight angle as seen at e (which angle is best determined by trial), and screwed by two screws to the spectacle frame, the frame being seen in section at d. In between the two Fig. 24 a and b represent one of these, of screws a small semicircle is cut out from the

21.-Adjusting Stops.

91

FIC.27

and a lock nut, also milled, which screw is to adjust the depth of cut. This bridge is fastened down over the end of the turning tool by the screws at the corners of the guide-plate, these

spectacle frame, which is seen by referring to Fig. 21. A milled-headed screw e, the threaded part of which is in. long and in. diameter, is made of brass to screw into the bent piece, in the position shown in the figure. A fine saw-screws, together with those at the opposite cut, f, runs from this hole outwards, and a rin. corners, serving to hold the guide-plate firmly to screw with a small head runs through the metal the spectacle frame. The edge end of the tool has at right angles to the saw-cut; the hole in one a small hole, b, to take one end of a moderately half of the metal having a thread for the screw, stiff steel spiral spring, f, the opposite end of the the other half being bored larger, so that the spring being fastened to the guide-plate by a screw slips easily through. small screw.

The edge of the turning tool, and the edge of the recording stylus, should be exactly in line with each other, this line being perpendicular to the longest sides of the guide-plate, or, more exactly, perpendicular to the line m, Fig. 21, The next adjusting stop, of which there are which joins the centre x to the point of the also two, is very simple, being a piece of angle adjusting screw resting on the guide-rod. brass or plate bent to the shape and filed out, as The guide-plate, with the turning tool mounted seen in Fig. 24 in elevation and plan at g and thereon, is fastened to the spectacle frame in the h; and, like the former stop, is fastened to the position shown in F, Fig. 27, or, as represented spectacle frame by two screws. These pieces by the dotted lines in Fig. 25, the turning tool come against the adjusting screws of the stop-being above the recording stylus. plate (Fig. 18, p. 133), when the spectacle frame is mounted on the bearing-post.

The tool is mounted, as shown in B, being pivoted in a forked support, c, made of brass rod in. square, this support being fixed to the guide- To set the shaft on table for drilling, place as plate by a screw, d, at the base. This guide-plate for planing. The gauge is made in two sizes, as is double the width of the one in Fig. 23, and follows:-No. 1 gauge is for shafting lin. to 6in. can conveniently be divided into two equal parts in diameter; No. 2 is for shafting 3in. to 12in. by a line, the position of the stylus guide then in diameter. Two bars, 3gin. and 6gin. long are being in the centre of one half, and the screw which holds the forked support coming on the pitcding line at in from the centre, as seen in nine to tel. This guide-plate has four holes at the of steel, hardened CAWS.