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 must be 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 exactly in 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 sides e, 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 large head 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 reach almost entirely 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 with one hole, 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.
HOLLOWING OUT WORK.
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 as willow, 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 or hard wood, 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. [You may, 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 out the 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.