Fig. 50.
Fig. 50.
You will certainly find a difficulty in turning all exactly alike the little pillars of these baskets. You should turn several at once out of the same piece, separating them afterwards. Thus your pattern will always be close to the half-executed copy, which will somewhat assist you. Do your best in this respect, but be specially careful, at anyrate, to make all exactly the same length. One pillar is shown separate, but you can design a pattern for yourself.
Begin by turning a long cylinder; then set off the respective lengths of the pillars. Turn one complete as a pattern, and set the callipers to the largest part of it. Then go to work upon a second, using callipers freely at all parts of it. As these pillars will all be slender, you will be in great danger of breaking them; therefore use your tools lightly, taking only a very slight cut. But with all your care you will find it difficult to turn a row of more than two or three of the size wanted for such little baskets. I shall therefore show you how to make a support to fit at the back of the bar you are at work upon to support it against the pressure of the tool.
Fig. 50 gives a representation of one or two such supports, which are often required in turning. The first is the most simple, and is the one most generally in use, because easy to make and to apply, and it answers tolerably well. A is merely a piece of wood, about three-quarters of an inch thick, cut as shown. This is stood up between the lathe-beds, like C, and fastened with a wedge before and behind. It allows the work in the lathe to revolve in the notch which is cut in it, as is evident from the drawing. One, two, or more such may be used if necessary. They must be carefully adjusted, so as not to bend the piece which is to be turned, and which is to be just supported, but no more. Wheretheback-stay, as this contrivance is called, comes in contact with the work, the latter is to be left of the size it was when this was adjusted to it as long as possible. It must then be shifted a little, and that part which formerly rested against it finished.
B is another simple form of back-stay, capable of nicer adjustment. The foot is that of a common rest, but if you have not a spare one, any wooden support is quite as good. Into this fits a turned part of the uprightx y,—the upper part,y, of this being planed flat. Neither should be of deal; ash or elm is preferable. Thus the partx ycan be raised and lowered at pleasure in the rest-socket. The top part is made of a half-inch board, about 2 or 2½ inches wide; a slit is cut in it, and it is fastened tox yby a short bolt and nut. Thus it is easy to raise and lower the end of this part, and to put it nearer to, or farther from, the work in the lathe, against which it can be adjusted with great nicety. Although there are several forms of back-stay, of more or less complicated construction, I know of none more generally serviceable than this last, which the young mechanic can make for himself. The notch should be lubricated with soap, or, if the blackness is not of importance (as when this part, which rotates in the notch, has finally to be cut away), with a mixture of soap and blacklead. This, remember, is always to be applied to wooden surfaces that are to work easily upon each other.
It will sometimes happen that you require to bore a hole through a long piece of wood, as would be the case in making a wooden pipe, flute, bodkin-case, and many similar articles. To hold these in a chuck only would be often impossible, because the hole in the chuck would have to be as deep at least as half the length of the piece to be bored.
For this kind of work, therefore, and for turning up a point on the end of a cylinder of iron or steel, like that of your back poppit, the following contrivance is used, which is called a boring-collar or cone-plate. It is represented in Fig. 50, D and E. This consists of a circular plate of metal, three-quarters of an inch thick, turning upon a large screw or pivot at its centre, by which pivot it is attached to a short poppit head, fitting between the bearers of the lathe as usual. There are six or eight conical holes bored round the circular plate, each of a different size; and these are so arranged as to height, or distance from the centre, that the top one (being in a perpendicular line passing through its centre and that of the bolt) is exactly as high as the axis of the mandrel. Thus, if it is clamped in that position, with the largest side of the conical holes next the mandrel, a piece of wood might be held at one end in a chuck, while the other might rest in such hole as was best suited to its size, not actually passing through it, but resting in the inside of the conical hole, in which it would rotate almostas freely and as truly as if it were supported by the ordinary point of the back poppit.
Sometimes it may be preferred to allow the end of such a piece of work to project through the cone-plate, a collar being turned on it to prevent it from going too far. A tool-handle, for instance, of the pattern before given, may be beautifully bored in the lathe by allowing the ferule to rotate in one of the holes of the cone-plate, the shoulder behind preventing it from going too far. The rest is brought round in front of the end of the handle, and a hole bored by a drill for wood; or, the point of a drill is brought against it, while the other end (having had a slight hole made by a centre-punch for the purpose) is allowed to centre itself on the point of the back poppit. The screw of the latter is then advanced, and the drill being prevented from itself revolving either by being grasped by the hand or a vice, a beautifully straight and even hole is rapidly made.
Fig. 50, F, shows the position of the various pieces. The drill is here kept from rotating by a small spanner, the handle of which comes against the bed of the lathe. A great deal of work, both in wood and metal, is always drilled in this way.
For wood, a small nose-bit, or auger-bit, or one of the American twist-drills, can be used, and this may be succeeded by a larger, until the hole will allow of the introductionof a finishing-tool of some kind, held in the hand. Of course the latter is not necessary in boring out handles for the tang of a tool, but only in turning boxes for pencils, needles, or other articles, which require to be neatly finished inside as well as out; all these are to be bored before the work is cut free from the superfluous wood out of which it was turned. You can even use the cross-chuck for this work.
It matters little, when using the cone-plate, whether you finish the turning of the outside before or after the boring is done. Very generally the box or other article is bored first, quite in its rough state, except that a short piece is turned down to fit into a hole of the cone-plate; and, keeping the latter in its place all the while, the wood is turned down and polished before removing it from the lathe. Sometimes, especially with metal, which is in no danger of splitting, the cone-plate is removed as soon as the hole has been made and replaced by the back-centre, the point of which, entering the hole, retains the work in its place while the outside is being fashioned. This of course insures the exterior surface being exactly concentric with the inside, which is often absolutely necessary in parts of machinery; but if wooden articles are finished in this way, there is great danger of their being split by the pressure of the back-centre as the work grows thinner and thinner under the action of the tools. Moreover, it mustbe remembered that the back-centre, being itself of a conical form, will injure the form of the hole in metal by making it wider at the mouth if used in this way, and sometimes this may be of importance.
There is a fault in the cone-plate which boys will understand, and men, too, I imagine.It costs money!Therefore I shall now show you how to make a substitute, which will cost something under a shilling, if you do not mind a little trouble; but, if you do, you will never make a good workman, nor will you be good for much, I fear, in any way! A metal cone-plate for a 5-inch lathe costs £2 at least.
I shall suppose you want a cone-plate in which to bore your tool-handles, for it is not easy to do this with a gimlet, so that the tools, when inserted, shall stand straight in their handles. If you have a 5-inch centre lathe,i.e., a lathe in which the central line or axis of the mandrel is 5 inches from the lathe-bed (in which case you can turn anything nearly 10 inches in diameter), cut out of a piece of beech, 3 inches thick, a short poppit 3½ inches high, of some such shape as seen in the fig. G; and in the lower part (which must be cut to fit between the lathe-bearers, and must be made square at the sides and true, so that the whole will stand squarely across the lathe-bed), either cut a mortice,a, for a wedge, or bore a hole for a screw, which must have a plate and nut to fasten under the bed like other poppits. Near the top, and exactlyin the centre, bore a hole to receive the bolt K, similar to that in the metal cone-plate already described, and which will be tightened by a nut at the back. This supplies the place of the short iron poppit, and now you have to contrive something to replace the circular plate of holes. Cut two or three strips of any tolerably hard wood, H (beech will answer very well), 6 inches long, half an inch thick, and 2 inches wide. Cut in these a slot and a round hole, which must be carefully made with a centrebit. This hole is to be for one of those in the usual round plate, so be careful in making it. Work thus: Plane up the piece from wood rather more than the half inch required; draw a line exactly down the middle of it on both sidese,f; choose a centrebit of the size you require; put the point upon this line, about 1½ inches or more, according to the size of the required hole, and bore steadily a little way into the wood. Then turn it over, measure carefully so as to get the precise spot right, and finish from that side. If the centrebit is sharp, and the wood sound, you will now have a neat round hole. Let the slot be also cut from both sides of the piece of wood with a sharp chisel, taking care that the centre of it agrees with the line that you made for a guide.
Three or four of these should be made, each with a different sized hole, or more if required; but you can add new ones at any time. The bolt, K, is to be made with a largehead flat on the under side, and the upper part, above the screw, is to be square for three-eighths of an inch, and the slot in the pieces of wood must just fit this squared part. Now, as this is three-eighths only, and the thickness of the wood is four-eighths or half an inch, it is plain that the nut will draw, and the head of the screw clamp this tightly. You can, if you like, however, make the hole in the poppit square also, and then let the squared part of the screw be long enough to reachalmostentirely through both pieces. Then slip a washer (an iron plate with a hole in it like L) over the end of the screw, and fix all with the nut. Thus you have a boring collar withonehole, and this you can raise or lower the length of the slot so as to get it exactly the right height, and when it is so arranged, one turn of the nut at the back will fix it.
This you will find a very simple form of boring-collar, easy to make, and of practical use. If you really take all the care you can, and follow the directions I have given, I do not see how you can possibly fail in constructing one. You should have a sliding-plate with a hole for each size of tool-handle ferule used, as you will frequently be making these.
As I have spoken of boring, I will go on to treat now of the general practice of hollowing out chucks and boxes, and such like. If this is to be done in soft wood, such aswillow, no tool will answer so well as the hook-tools, of which I have given drawings. But these are very difficult indeed to use, owing to their tendency to catch in, or take suddenly a deeper cut than was intended. Nothing but practice will teach exactly how to use these tools; but then, when the difficulty of so doing is once mastered, nothing can be more rapid or more satisfactory than the work which they will do. Small bowls are hollowed almost instantaneously by their means in skilled hands; whereas, with other tools, it becomes not only a tedious job, but if it is done at all, it is but roughly, the wood having to be rather scraped out than cut. Using, however, the back of the gouge as explained before, in the directions given for squaring up the end of a cylinder with this tool, it is possible to hollow out soft wood with it, but not very satisfactorily. In any case, other tools (generally a carpenter’s chisel) must be used to work into the angle which neither the gouge nor hook-tool can, of course, reach. Hence it is generally so much easier to cut out boxes and such like articles in box orhardwood, that this is nearly always used by amateurs.
The ordinary way to turn a box is as follows:—Prepare the wood as usual, turning it cylindrical, using any chuck you please for this work; cut off with the parting-tool rather more than the box and its cover together will require, and drive the piece thus separated into a cup-chuck. [Youmay, if you prefer it, screw upon the nose of the mandrel, or upon the taper screw-chuck, the rough piece of the proper length, instead of first turning a cylinder to cut from. If you have several boxes to make of one size, the cylinder method is to be preferred.] Turn it up again quite true, for although it was correct before you cut it off, it will not be so now. Square up the end, and turning round the rest so as to stand across the face of the wood, begin to hollow outthe cover. Use either the round end or pointed tool at first, and then a carpenter’s chisel or flat tool to finish. Be very careful that the sides (I must call it by this name, although a circle has not more sides than a plum-pudding) are turned square to the bottom, or else, when the cover is put on, it will perhaps fit just at the entry, and be quite loose when fairly on; or, it may be that it will be easy at first, and when you press it on, it will be tighter and become split,—a very common but unpleasant occurrence. Do not, moreover, turn down these sides as thin as they will ultimately be; because, after the box is hollowed and the cover fitted on, both will have to be slightly turned together to finish them nicely. Moreover, you may not wish your box to have plain sides, but may prefer to mould them into a more elegant form. All these little questions have to be duly considered in turning, for a mistake is often made, and the work spoiled, for want of a little timely consideration.
The next point on which you have to be on your guard is this,—having turned out the cover, you have to cut it off, not with a saw, but with your parting-tool. Now, be sure to leave thickness enough for the top of the cover; or, just as you think you have nearly severed the latter from the rest of the piece of wood, you will see a beautiful little ring tumble off,—sad relict of your box cover, which has come to an untimely end.
The sliding square of the turner, of which I gave a description among the list of tools, will always enable you to gauge both the depth to which the work is hollowed out, and also the squareness of the inside to the bottom. But if you have no turner’s square, you can easily gauge the depth inside, and thus see how much is necessary to be allowed for the thickness of the top. Keep the parting-tool edgewise on the rest, which should be raised to such a height that, when this tool is laid horizontally across it, it will point nearly to the centre of the work,i.e., the axis of it. After the parting-tool has cut into the wood a little way, widen the groove a little, and continue to give the tool a little play right and left, unless its end is so much wider than its blade generally that it will clear itself perfectly as it goes deeper and deeper into cut. If it should bind, it is almost certain to break, for it is a very thin tool; and it is better to waste a little more of your material than to have to replace a spoiled tool.
I shall suppose that you have now succeeded in cutting off the cover; pick it up and lay it near you. Directions are given generally to turn down next the flange upon which the cover of the box is to be fitted, but this is not to be wholly done yet, and you may proceed to hollow it out as soon as you have turned down just so much of this flange as will show you how much to leave in hollowing out the box. If youfitthe cover before you have hollowed out the box, you will have the mortification of finding it a great deal too loose when the box is finished, because the latter will contract in size as soon as ever the solid core is removed from it.Afteryou have hollowed it out, you must gauge the inside of the cover, and the outside of the place that it is to occupy, with the in-and-out callipers, or with a common pair, and turn the flange till it is almost correct to this gauge, and only a very little larger than it ought to be. When this is the case, do not trust any longer to the callipers, but try on the cover again and again until you get a nice fit. You must finish the flange with a chisel, held flat; and again I repeat the caution about keeping it truly square, so that the cover will hold equally tight in all positions. When this is the case, leave it on, and give a last touch to both box and cover together, when you ought barely to be able to see the joint.
You have now only to cut off the box as you did the cover, using the same precautions. Before it is quitesevered, however, you should give it a polish. Pick up a handful of shavings, and while the work is revolving as rapidly as possible, hold them with some pressure against it. Every fibre will be at once laid smooth, and it will look nice and bright at once. You can varnish it afterwards if you like, or French-polish it. Varnish is best for boxwood, and French-polishing requires special directions, which I shall give you separately in a future page.
To be able to make a boxwell, with its cover well fitted, is to be able to do all kinds of similar work. Yet in these may be specialdetailsdeserving notice. Probably, therefore, when speaking in a future page of particular objects which have to be turned, such special details will be more fitting than if given here. I shall therefore pass on to another part of the subject, namely, screwed and twisted work.
Neither of these can be very accurately made without special and somewhat expensive apparatus; but both can with practice be done tolerably well by the young mechanic with ordinary simple means. I need not describe a screw, for all boys know what it is; and sporting boys, of which in these days there are many, know what sort ofanimala screw is. Well, never mind. I am always riding a screw, I believe, for it is my hobby, and there is a great deal ofscience in a screw; and as for thevarietyof the manufactured article, there is plenty of it. There is the corkscrew, which is, after all, not a screw, but a twist,—and this is often the means of making men screwed; and the miserly screw, who skins fleas for the sake of their fat; and there is the mythical, invisible, moral (and im-moral) screw, which hard-fisted men inflict upon their weaker brethren; and there is the gigantic screw of theGreat Easternsteamship; and the minute, microscopic screw of the lady’s tiny jewelled watch.
There are several modes of cutting screws, in the lathe and out of it. The small ones required for holding together the different parts of machinery, as well as larger ones for the same purpose, are always cut with stock and dies. The very small ones used by watchmakers, and all below one-eighth of an inch diameter, are made by the screw-plate. But when either large or small screws are required of great accuracy, they are invariably cut in the lathe, and with the aid of mechanical appliances of the most delicately accurate description. These are all metal screws. But the young mechanic will often wish to put screwed covers to his boxes, and to join various parts of his work by screwed connections instead of glue; and all these may be cut in the lathe by simple hand-tools skilfully applied, although the operation is sufficiently fraught with difficulty to require a great deal of practice before it can be done with certaintyof success. At the same time, my young friends cannot possibly do better than practise this operation, for there are numberless cases in which screws cannot be conveniently cut in any other way, and it is, further, an accomplishment that will at once stamp them as skilful workmen.
Fig. 51.
Fig. 51.
The tools required are represented at A, B, Fig. 51. A is an outside, and B an inside screw chasing-tool. These are always made in pairs, of exactly the same pitch,i.e., the outside tool being applied to the inside, the respective notches and points will exactly fit into each other. If you were to examine the under side of these tools, shown at C, you would notice that the notches do not run straight, but slanting. They are in fact parts of screw threads; and youcould make a tool of this kind out of a common screw nut, as I have shown you at D, only it would be too much hollowed out to make a good tool.
Now, supposing you were to hold the tool A flat on the rest, while a cylindrical piece of wood revolved in contact with it, you would cut a series of rings only; but if you were at the same time to slide the tool sideways upon the rest, so that by the time the wood had revolved once, the first point of the tool would have just reached the spot which was occupied by the second when you started, you would have traced a screw thread of that particular pitch. This is what you have to learn to do always, and with certainty, no matter what pitch of tool you may be using, and it is easy to understand how difficult the operation must be to a beginner. Indeed, there are numbers of otherwise good turners who have never succeeded in mastering this work. Nevertheless it can be done, and, although difficult, it is not so much so as might be supposed. Indeed, at first sight it would hardly be believedpossible, because each different pitch of tool, and each different-sized piece of work, requires a different speed of traverse to be given to the tool. But a practised hand will strike thread after thread without failure, and those whose trade is to make all sorts of screw-covered boxes and similar articles, will execute the work with as much speed and apparent ease, as they would any ordinary operation of turning. I shall tell youby and by, however, of several ways to escape this difficulty of screw-cutting,—lathes being fitted in various ways to insure good work, in some cases by carrying forward the tool at exactly the right rate of traverse, and at others by moving along the work itself at the proper speed, while the cutting tool is held immovably fixed in one position,—and I will give one tool of great service which will guide you in starting the ordinary chasing-tool; and a good start is here truly “half the battle.”
The chasing-tool must run from right to left for an ordinary right-handed screw (and a left-handed one is very seldom required), so that the young mechanic need not trouble himself about it. Precise directions cannot be given further than to have a rest with a very smooth and even edge, which will not in the least hinder the traverse of the chasing-tool, and to get the lathe into steady, equable motion. Then hold the tool lightly, but firmly, keeping it at right angles with the work. Allow it only just to touch until you find you have got into the rightswing. It is all a matter of knack and practice; and if you succeed quickly, you may congratulate yourself.
The inside chasing-tool is used in precisely the same way, running it from the outer edge of the hole inwards. To some this is an easier tool to use than the outside chaser. I cannot say that I find it so; especially as one has to work more in the dark; unless the work is of largediameter like the cover of a box, and even then the work is sufficiently difficult owing to the shallowness of the lid, which necessitates the instant stopping of the tool for a fresh cut. For you must understand that you have to deepen the screw-threads very gradually, and it will take several traverses of the tool to cut them to a sufficient depth.
The chasers require to be very sharp to cut wooden screws neatly, but observe you must only rub the upper flat face upon the oilstone, or, if a notch has been made by using the tools upon metal (they will cut brass well with care), grind them in the same way; the great secret being to hold the tool quite flat on the stone. You will thus, even by continual grinding, only thin the blade of the chaser, which will thus last for a long time. A practised hand will even cut a good thread with any flat piece of steel filed into equal notches, but a screw-chaser is the only tool really fit for the purpose.
Fig. 52.
Fig. 52.
The most effectual remedy for the screw-cutting difficulty, is unfortunately rather expensive in its best form. But in another, it is by no means costly; and although it may not look so well as the first, it is equally effective, and extensively used by the turners at Tunbridge Wells, who make those beautiful little inlaid boxes and other articles. I shall explain this to you, therefore, first:—
A, is a lathe-head, something like the one I have alreadydescribed, but you will notice that the mandrel is a much longer one, and has several short screws cut upon it, each one being of a different “thread” or “pitch.”[1]This mandrel runs through two collars, so that, besides turning round, it can be pushed endwise. Now, supposingI was to hold the point of a tool firmly against either of the screws, and at the same time was to turn the pulley and mandrel, you will understand that it would run backwards or forwards in its collars, at such a rate as the screw-thread compelled it to move. This is the plan of the traversing mandrel; and now supposing that you had a box held as usual in a chuck, and while the mandrel was compelled to move endwise as described, you were to hold a pointed tool against it, the tool would evidently cut a screw-thread of exactly the same pitch as that upon the mandrel against which the pointed tool first spoken of was applied. But in practice, a single-pointed tool held against the mandrel would not answer very well, and so the following plan is adopted instead, which answers perfectly.
Fig. 52, C, is called a half-nut. It has a set of screw-threads, cut where the semicircular hollow is, which threads fit one of the screws on the mandrel. A whole row of these half-nuts are fitted to turn at one end upon a long bar, so that either one can be raised up at pleasure to touch the screw upon the mandrel, which has threads of the same pitch as itself, B. These, then, are ranged under the mandrel, and when it is desired to make it traverse in its collars, one of these half-nuts is raised and kept up by a wedge placed underneath it. When no screw is required, a somewhat similar half-nut, but with merely a sharp edge instead of a thread, is raised, and this edge falls into anotch or groove turned upon the mandrel, or sometimes a back centre-screw is added like D, and when no screw has to be cut, this is run up against the mandrel like an ordinary lathe.
In the more expensive traversing mandrels, although the principle is the same, there is a little difference in the arrangement of the different parts. The mandrel is not very much longer than usual; and it has no screw-threads cut upon it. But a number of ferules like K, are made each with a screw upon its edge, and one of these of the desired pitch is slid upon the end of the mandrel atb, fig. P, and is there held by a nut or otherwise, so that it cannot move out of its place. The half-nut is seen ata. It consists of a piece of brass or steel of the form shown with a hole in the middle, and a screw cut uponeach hollow, so that it is a circle or set of half-nuts of different pitches. This slips over a pin ata, and when the screwbis turned, it draws up this pin and the nut attached, until the latter comes in contact with the ferule upon the end of the mandrel. This is very neat but expensive. Now, by far the cheapest and best way for the young mechanic, is to set boldly to work to conquer the difficulty of chasing screws by hand. There are even disadvantages in the expensive form of a traversing mandrel, which render it by no means a desirable mode of fitting up a lathe, and after all, the length of screw which it enables one to cut is very limited,and in addition, it is not every day, nor probably once a month, that screw-cutting will be necessary at all. My advice, therefore, is, do not get a traversing mandrel until you can cut screws well with the chaser. When you can do this, you will be able to judge of the advantage or disadvantage of one.
By far the greater number of common screws are cut without the lathe, by screw-plates, or stocks and dies, and the nut, or hole into which such screws are to fit, is cut with a tap. A screw-plate is a simple affair,—a mere flat plate of steel, in which several holes are drilled, which are afterwards threaded by screwing into them taps, or hard cutting steel screws of the size required; the plate is then hardened by being heated red-hot and suddenly cooled, after which being much harder than brass, iron, or steel which has not gone through such process, it will in turn cut a thread upon any of these by simply screwing them into it. But although this will answer for small and common screws, it is not at all suitable for better ones, because the thread isburredup, notcutcleanly as it would be with a proper tool. A far better plan is a stock and dies; the latter being practically a hardened steel nut sawn in half, and fitted so that the two halves can be pressed nearer and nearer together as the screw thread becomes deeper. The dies are screwed up by means of a thumbscrew opposite to the handle.
To use it, a piece of iron is filed up or turned to the required size, which must be exactly that of the finished screw. The dies are then loosened and slipped on to the end of this screw-blank as it is called, and are then slightly tightened upon it. All that is now required is to keep turning the tool round and round upon the pin, which it will soon cut into a screw thread. When the stock is at the bottom or top, you may tighten the dies, and so work up or down; but never tighten them in any other part. If iron or steel is to be cut, use oil with the tool, but brass may be dry. If the screw is of steel, heat it red-hot and let it cool very gradually, to make it as soft as possible.
The hole or nut, into which the screw is to fit, is to be drilled so as just to allow the taper tap to enter about a couple of threads; a wrench, or, if small, a hand-vice is then applied to twist it forcibly into the hole, when the thread will be completed. Take great care to hold the tap upright, or else, if it is a screw with a flat head which has to fit into it, it will not lie correctly, but one side of the head will touch while the other is more or less raised.
There are other modes of screw cutting, but at present I need only mention one, which is used for wooden screws alone. It is called a screw-box, and is only made to cut one size, a tap being always sold to match. You can, however, purchase any size you like, from a quarter of an inch to 2 or 3 inches; but the latter are only intended for verylarge screws, such as are used for carpenters’ benches and various kinds of presses. A screw-box looks like a small block of wood with a hole in it, but if you take out two screws you will find a blade of a peculiar shape, which forms the thread by cutting the wood as it is screwed into the hole in the box.
We now discard almost entirely the gouge and chisel used for soft woods, and fall back upon an entirely different set of tools, similar to those used for metal, but ground to rather more acute angles. These tools are held horizontally upon the rest, because depressing the handles causes the bevel below the edge to rub upon the work; and in addition, the grain of hard foreign woods is such that it cannot well be cut by placing the tool at a more acute angle, as would theoretically be required. Hence we can only regard these as scraping tools; but as such they will do excellent work in skilful hands. I have said that we discard the gouge, but there are some woods that will bear this tool, to take off the roughest parts of the work, before the application of others. The roughing-tool, however, may now be considered to be the point-tool, and the round-end tool, or “round” as it isoften called; a narrow one makes a good tool for this purpose.
Hard wood is easier on the whole to work than soft, because we have for the purpose a large stock of tools of all shapes, suitable to the various mouldings required. Hollows, round-beading tools, compound and simple moulding tools of various sizes, to say nothing of those which are made for use with ornamental apparatus, such as are required for fluting, beading, and eccentric work, spirals, and so forth. It is indeed in hard wood that most amateurs are accustomed to work; ebony and ivory, singly or in combination, being more extensively used than any other.
To turn a cylinder, or any work requiring to be held at both ends, you will invariably find the cross-chuck the best to use,—the fork or prong not taking hold in the hard material. Rough down to shape as before, using the gouge if it will work, but keeping the rest as close as possible, and only taking a light cut. Then finish roughing with a round-tool, and proceed generally as in soft wood turning, except inasmuch as you have to scrape instead of cutting the work into form.
In addition to the tools already described, you will have to obtain a few beading-tools, if you want to do very good work, for these give far more beautiful mouldings than you can cut in any other manner. Fig. 53, A to C, representthese. The bevel is on the under side, and it is better to interfere with it as little as possible, by always sharpening the flat face only. If it should benecessary, however, to touch the bevel, it must be rubbed by a slip of oilstone, rounded on the edge, as used for sharpening gouges. Conical grinders, revolving in the lathe, are also used, especially for small beading-tools, to be fixed in the slide-rest. In the same figure, D and E represent another useful hard-wood and ivory tool. It is called the side-parting tool; and it is usual to have several of these, the hooks increasing in length. The edge is only on the extreme end of the hook. These tools are used for economy’s sake to cut solid blocks of ivory and hard-wood from the inside of boxes, instead of cutting the material into a heap of useless shavings. Similar tools, G, H, curved instead of rectangular, serve to cut out a solid piece from the inside of a bowl. In ivory work it is essential to use these tools, because such material is very costly; $2.50 a lb., and upwards, being a common price.
Fig. 53.
Fig. 53.
K is given to show what are meant by beadings. If these are exactly semicircular in section, they are far more beautiful in appearance than if of such curves as can be roughly cut by a chisel. The bead-tools are beautifully formed for this very purpose. To use the same side-parting tool, you must proceed as follows, which you will understand by the fig. L:—A common straight parting-tool ornarrow chisel is first applied to the face of the work to cut a deep circular groove or channel, as shown by the white space at N, and in section at L. This allows the narrowest of the hooked tools to be applied tounder-cutthe solid corex. This being withdrawn, a rather longer hook is applied, the hook being held downwards as at O, until it reaches the spot where it is to work, when it is gradually turned up (bevel below). Eventually, it is plain that the solid core or centre blockxwill fall out entire, which may be used for other purposes. M shows how a similar but curved block can be removed from the inside of a cup or bowl, the curved tool not requiring an entry to be made for it, as it cuts its own way entirely from first to last.
P and Q show a ring-tool and the method of using it. A recess is turned in the face of a piece of wood as if it was intended to hollow out a box. The ring-tool is then applied bevel downwards, and with the left cutting edge a bead is cut half-through from the inside. The right edge is then applied to the outside, and when the cuts meet the ring neatly finished, will fall off. With this tool you can turn them very rapidly, and they will require only a rub of sand-paper to finish them.
R, S, T are three more tools for hard wood. The first two cut on the outside of the curved part all round. These would be used to hollow out humming-tops and all similararticles, and to finish the insides of bowls, for which T is also designed. Indeed, I might go on to describe all possible shapes of curved tools, each intended for some special work; but you will not do better than to go to Fenn, Buck, or any tool-maker in London, or elsewhere, and pick out at 7s., or so, per dozen, all shapes and sizes, or if you live at a distance and write to either of the above, they will select you the most useful; and you can trust these tradesmen and all first-class ones to send you no tools which are not of the best quality.
In finishing best work in hard wood, be very careful of all sharp edges of mouldings. Sand and glass paper round off these, and spoil the beauty of the work. If you areobligedto use such substances, touch off again the edges with very keen tools, which ought to leave brighter and more beautiful surfaces than any sand-paper can produce. Indeed, the secret offinishedwork in hard wood is to have tools whose edges and bevels arepolished. In ornamental eccentric and rose-engine turning, where to use sand-paper would be to ruin the appearance of it, the little drills and cutters pass through three stages of sharpening, being ground on the oilstone, finished on a slab of brass, fed with oil and oilstone powder, and polished on a slab of iron with oil alone or oil and rouge. After this every cut that is made with them reflects the light; and as the surface is otherwise purposely grailed or dulled by cutting a series of fine lightrings with a point tool, the pattern itself shows out clearly and lustrously.
I shall now teach you how to turn iron and brass, which, though harder than wood, are not very difficult to cut, if you go to work in a proper manner and understand how to use your tools. What these are like I have already told you, and also how to mount a bar in the lathe by using the driver or point-chuck with a carrier. If the piece to be turned isnota bar, you will have to drive it into a chuck of wood, or clamp it upon a face-plate, or in a self-centring chuck if you have one.
I shall suppose, first of all, a mere straight bar of iron, centred at the ends, as I have shown you. Take off the lathe-cord that you use for wood, and fit one to go upon the largest part of the mandrel pulley, and the smallest upon the fly-wheel. When you now put your foot upon the treadle to work at your usual speed, you will find the mandrel turn quite slowly; but I may at once tell you, that what you lose in speed you gain in power. Set your rest for iron (which is not that used for wood, but one with a broad, flat top) so that it stands a little below the central line of the lathe mandrel and work, which will bring the edge of the tool exactlyuponthat line. This is always the position of the tool for metal-turning, at any rate for iron.
Begin by trimming the end of the bar next to the back centre. Use a graver, held as I directed you; that is, with the bevel flat upon thefaceof the iron, which is in this case theendof it. Only let the point cut, and a very little of the edge beyond it, and do not expect to take adeepcut so as to bring off a thick shaving. In metal work you will always have to proceed slowly, but nothing is more pleasant when once you can do it well.
You will at first have to experimentalise a little as to the exact angle at which to hold the tool, but you will soon find out this; and the advantage of hand-tools is, that you can alwaysfeelas well asseehow they are working, and can ease them here and there to suit the material. It is rather difficult at first to hold the tool still in metal-working, but, like all else, it becomes easy by practice; so much so, that to hold the tool steadily in one hand is not only possible, but is the mode always followed by watchmakers. While you are about it, you should turn the graver over and try it in other positions; for although the two sides of the bevel nearest to the point are the only ones to be used, these may be applied in either direction, because they are both sharpened to angles of 60°, and so long as you present them at the correct angle (the smallest possible in respect of the work), it matters not which face of the tool lies uppermost. After squaring off one end, the approved plan is to remove the carrier, reverse the bar, and do the same to the other end. Then begin toturn from the right hand. Place the graver as before, with the point overlapping the end very slightly (so as only to use the extremity of the cutting edge close to the point), and take off a light shaving along the bar for a distance of about half an inch, or even a quarter, keeping the edge of the graver which is on the rest in one position, and moving the tool, not by sliding it along the rest, but by using the point upon which it lies as a pivot. It is very difficult to describe this exactly, but Fig. 52, O, will help to explain it. The tool is to rest upon one spot, and the point to move in short curves like the dotted lines, being shifted to a new position as you feel it getout of cut. The left hand should grasp the blade and hold it tightly down upon the rest, while the right moves the handle to and fro as required. The curved dotted lines are necessarily exaggerated, but theprincipleof the work is this, whether you use a graver or a heel-tool. You should turn about half an inch quite round, and then go on to the next, by which you will always have a littleshoulderupon the work for the tool to start upon, and this will be nice, clean, bright metal, and will not blunt the tool. But if you go to work differently, so that the edge of the tool comes continually in contact with the rough outside of the iron caused by the heat of the fire, and which is exceedingly hard, the point of the tool will be quickly ground down, while the iron will not be cut into at all.
I need tell you no more about turning abarof iron in the lathe, because the above directions apply in all cases; but if you have to turn thefaceof a piece of metal that is carried in a chuck of some kind, you should always workfromthe middle towards the edge, and if the graver is used, its bevelled face will lie towards you during the process. Take care to chuck the metal very firmly, for it is most annoying to have it suddenly leave the chuck or shift its position after you have been at the trouble of turning part of it truly. In such case it is very difficult to replace it exactly as it was before, and all your work has in consequence to be gone over again. When taking the final cut, or before, if you like, dip the end of the tool into water, or soap and water, and see the effect. The surface turned in this way will be highly polished at once, and the tool will cut with much greater ease, so that a large, clean shaving will come off. When using a slide-rest, you will find it always better to keep water just dripping upon the work and point of the tool; but there is a drawback, nevertheless, to this plan, for, as might be expected, it makes a mess and rusts the lathe, and sometimes the work as well, so the water must be constantly wiped off it.
I shall now pass on to describe a mechanical arrangement called a slide-rest, of which there are two separate and distinctforms, one for metal and one for ornamental turning in ivory and hard wood. The ornamental work that can be done I shall pass by for the present, because few boys are provided with the costly apparatus required, and I am rather addressing those young mechanics whose tastes incline them to model machinery and to practise the various operations of mechanical engineering on a small scale. To such a slide-rest is analmostnecessary addition to the lathe, for there is a great deal of work which, I may say, cannot be done without it; for instance, boring the cylinders of engines (except small ones of brass), turning the piston-rods and various pieces which require to be accurately cylindrical and of equal size, perhaps for the length of a foot or more. Hand-work has accomplishedsomethingin this way in olden days, but the inability of workmen to advance beyond a certain standard of perfection with hand-tools alone, became such a hindrance to the manufacture of the steam-engine, as improved by Watt and others, that had not Maudsley, Naysmith, and others developed the principle of the slide-rest and planing machine, we should not yet have lived to see those gigantic engines which tear along like demon horses with breath of fire, at the rate of sixty miles or more in as many minutes. So likewise would various other machines, which now appear absolutely necessary to supply our various wants, have stood in their primitive and imperfectly developed forms; for it is necessary,before constructing a machine, to have the means of turning cylindrical parts truly, and producing perfectly level plates where required.
The object of a slide-rest is to provide means for holding a tool firmly, and giving it a power to traverse to and fro and from side to side, so that by the first we may be able to cause such tool to approach or recede from the work, and by the second we may cause it to move in a perfectly straight line along its surface from end to end. This is accomplished in the following manner:—The drawing being a representation of one of the first machines constructed for the purpose. A rectangular frame, A, of iron is carried by a pair of strong uprights, B B, fixed to the sole-plate, C, by which it is attached by a bolt to the bed of the lathe. Lengthwise of this frame runs a screw, prevented by collars from moving endwise, but which can be turned round by the winch-handle, D. Thus a nut through which this screw passes, and which only has endwise motion, will, when the latter is turned by its handle, traverse it from end to end in either direction, according as the screw may be turned from right to left or the contrary. This nut is attached to the under part of a sliding-plate, E, which has a part projecting between the sides of the frame, and also two others on its outside, by which it grasps the same with great accuracy, and is prevented from any shake or play as the wholewith the nut is made to traverse to and fro along the frame.
Lengthwise of this sliding-plate, that is, in a direction the opposite to that of its own traverse, are two bars bevelled underneath, fixed exactly parallel to each other, which are so arranged to guide the cross traverse of another plate with chamfered edges to fit the bevels of the guide bars. This second plate has on its upper surface two clamps which secure the tool. It is plain, then, that by this arrangement the two required movements are attained, the lower plate sliding along in one direction parallel with the lathe-bed, and the other across it. In the original rests, this upper plate with the tool was moved by hand, and in the modern rest for ornamental turning (which this was also constructed for) the same is done, but a hand-lever is added for the purpose.
But although a similar arrangement is needed for metal, it is plain that the top plate should have a more easily regulated motion, and that we should be able to advance the tool as near the work as may be desired, and then to retain it securely at that distance while giving the necessary movement in the direction of the length of the object to be turned. The method of effecting this is at once suggested by the screw and nut of the lower part, and by merely adding to the top a similar arrangement, the desired end is at once attained.