CHAPTER XII 
SPINNING 
The lathe-The pattern or forme-The section chuck-Other cucks followers—-Tools—Spinning—Lubricants. 

The bowls, stems and feet of cups, and hollow vessels of almost any form may be produced from discs of sheet metal by burnishing them into shape on a lathe. This process is known as spinning. It is applicable only to shapes which are circular in section : though the form of the work produced may, of course, be afterwards altered by the use of snarlingirons, or by shaping and planishing it on suitable shapes.Thus, the general form of Fig. 161 could have been produced on the spinning lathe, the flutes or lobes being afterwards snarled and hammered out. But, primarily, spinning is employed for shapes which are circular in plan, whatever their profile may be. The process is in very general use among manufacturing silversmiths, to whom the ease with which a number of exactly similar copies of a shape may be produced is of importance. It has, however, little interest for the artist, for to him variety and a less mechanically smoothed surface naturally appeal. 

The principal tools employed are the lathe, the pattern or forme, and the burnisher or spinning tool. We will look at these each in order and afterwards see how they are used. 

Considerable speed being necessary, backgearing is not required in the spinning lathe. Almost any single-gearedlathe which is large enough may be used. Small work maybe spun Avith a foot lathe, but, as in wood-turning, anydiameter greater than about five or six inches means very hard work unless you have power. A speed of from 800 to 1200 revolutions per minute is necessary for the metals with which we are dealing. The thicker the metal, the less the speed required. The rest employed is like the ordinary T-rest of the wood-turner, Fig. 175. It has, however, a row of holes drilled in its top edge. Into any conveniently placed one of which a stout steel peg, known as the " pin," is dropped. Its use is explained below. The tailstock is similar to that used for turning, but it is often fitted with a revolving centre. In this case the centre, which is not tapered, rests against one or two hardened steel buttons which take up most of the friction, Fig. 166. 

The forme, pattern or chuck upon which the metal is spun plays a very important part in the work. It is a block of wood or metal of the exact shape of the bowl required ; though it is made smaller than the design by just the thick ness of the metal employed for the bowl. When the shape of the bowl is such that the pattern can be withdrawn from it when the spinning is completed, Fig. 167 for example, the pattern is made in one piece. But if the shape would not allow of this, and you do not wish to destroy the pattern after it has done its work, a section chuck must be em ployed instead. The forme or pattern is generally of well-dried maple. The block from which it is made is bored and tapped to fit the nose of the lathe, and then turned to fit a templet which has been set out from the drawing. Due allowance is made for the thickness of the metal which is to be used for the bowl. 

For a shape like Fig. 171 a sectional chuck would be used. It would be made as shown in section in Fig. 172. The part A is fitted to the nose of the lathe by the screw shown in the drawing and extends as a thick parallel-sided pin, B, to the bottom of the bowl. Round it, completing the shape of the bowl, are a number of movable pieces, D, Figs. 172, 173. At least one of these, a " key " section, C, Fig. 173, has parallel sides. It is always rather thinner than the pin or core of the chuck B. When a bowl has been spun on to the chuck, the bowl and the movable sections are together pulled lengthwise from B, the core of the chuck. The key piece may then be wriggled free. It has room to shift now that the core has been removed. The remaining sections come out easily, and are replaced at once round the core, and the chuck is ready for the next bowl. Sometimes patterns are made with more than one key piece, but unless at least one is provided the radial pieces could not be removed. The projectingringEonpieceAfitsintoagrooveinthe movable sections and keeps them together. The shape, or " stock," or " shell," as the bowl is sometimes called, would be spun up as far as possible on another (a simple pattern), before being transferred to the section chucked for completion. Another form of section chuck suitable for a deeper bowl is shown in Figs. 176 to 179. Yet another kind, known as a plug chuck, is shown in Fig. 174. It is used for shapes which are constricted in the middle and open at each end. The bottom of the shape spun on Fig. 174, must, of course, be cut out before the movable section F of the chuck can be removed. A shape like this would, however, be more easily spun from a tapered tube than from a disc. 

Yet another kind is the nailhead chuck, Fig. 168. It is made from a hard wood, such as boxwood. This chuck is used for turning inwards the lip of any small bowl or dish. It thus saves the expense of making a sectional chuck for a shape like Fig. 169. The diameter of the chuck must be less than the mouth of the complete bowl. The chuck is rubbed with powdered pumice and water to make it grip the work. The latter, which has already been spun as far as possible on another chuck, is slipped over the nailhead and kept in position with the finger. With a little trouble the edge G, Fig. 170. may be worked round to the curve shown in Fig. 169. 

A bowl such as Fig. 180 can be made without the aid of a section chuck. It is spun on an ordinary pattern which fits it from the bottom to as far as the angle H. By the time that the bowl has been spun thus far the rim will have taken a curve something like that shown by N, Fig. 188. A hooked tool K, Figs. 181, 182, is now clamped firmly to the rest or to the lathe-bed. Seen from above the rounded end of the tool "takes up "-or continues the curve of the pattern beyond the corner H. The tool, of course, does not rotate, as the pattern does, but it remains permanently near the corner H, and so supports the boAvl against the pressure of the spinning tool. The bowl can, therefore, be spun to the required shape just as though it were on a section chuck. In some cases a hole is drilled through the shank of the tool at J, and the tool slipped over an extra pin in the T-rest. It may be held in place by an assistant. 

A shape like Fig. 167, say for the base of a cup, can be spun without difficulty. Even if the mouldings are under cut, as in Fig. 183, it would not be impossible. If the pattern were required again it would be necessary to cut away first those parts of it which would bind when the metal was spun over them. The metal at those places Avould be spun without support, " in the air " as it is called. 

The decoration of a bellows pipe, such as Fig. 184, can be effected by holding the tapering pipe or tube between centres or arbors, and spinning it to shape without any further support inside. The baluster stem of a cup may be spun in the same way. But it is better to turn a wooden pattern to the required shape first; to slip the tube from which the stem is to be spun over the Avooden pattern, and then to spin the metal hard down against the wood. The latter may be burnt out afterwards. 

The disc of metal from which a bowl is spun is kept in position against the forme by a small block of Avood known as the " folloAver." The latter in its turn is supported by the revolving centre of the tailstock. This is shown in Fig. 188, where L is the head of the lathe, M the forme, N the blank or disc of metal which is to being spun, 0 the folloAver, P the revolving centre, R the tailstock, S the rest, T the pin, and V the tool. Followers are made in different shapes Avithflatorhollowfaces,Figs. 185to 187.The importantthing to notice about them is that as large a follower as possible is ahvays chosen. With a large follower the disc of metal is not so likely to jam and stop rotating; for the grip of a large folloAver is so much greater than that of a small one. Nevertheless, some difficulty is frequently met with in spinning a shape like No. 189 as so small a part of the pattern would be in contact with the disc of metal at first. Spinners frequently flatten the bottom of the forme like Fig. 190, just to give a better grip. They also rub pitch or powdered pumice on it for the same reason. Another way to obtain the same result is to raise a good-sized shallow bump in the centre of the disc of metal to be spun. This bump may be pressed almost flat again between the forme and the flat follower by screAving the tailstock tightly, and the extra pressure obtained in this way will naturally give a better grip. 

The tools are longer and heavier than those used by Avood-turners. Including handle, they measure from tAvo to three feet in length, and may be from half an inch to an inchinthickness. Theyare forgedfromtoolsteel,hardened, tempered, and polished very brightly. They are made in a number of shapes, but that shown in Fig. 191 is perhaps the most convenient for general use. It, like all spinning tools, has a smooth, highly polished surface with no sharp angles or corners which might cut or tear the metal. Fig. 192 is a similar tool but with flat face for smoothing up. Fig. 193 is a ball tool which goes into curves rather well. Fig. 194 is a hook tool useful for a variety of curves. Another tool is a pair of long handled pliers, the jaAvs of which have been bent round in a curve, Fig. 196. The inner edges of the jaAvs arecarefullyroundedandpolished. Theedgeoftherotating disc may be seized lightly Avith the tool and bent round in a quick curve to form a bead, the shape being completed Avith the aid of a hollow-faced wheel tool, Fig. 197, which is known as the beading tool. The diamond-point, Fig. 195, made from a square bar of steel, is useful for cutting the edges of the Avork true. It is the ordinary metal-turner's hand tool. If the metal Avhich is being spun is thick enough shallow mouldings and lines are sometimes turned in it, and its surface smoothed up with a sharp-edged turning tool. The work may also be smoothed with emery cloth and polished, while still on the forme. The backstick is a piece of hard wood which is held in the left hand against the reverse side of the rotating disc when the spinning tool is working it into shape. The backstick is of great assistance in keeping the edge of the disc from wobbling or getting into pleats. It should follow the tool about as it moves. 

To spin a bowl, Fig. 189 for instance. First turn in the lathe a forme of the right shape, but flattened at the bottom a little to give a better grip, Fig. 190. Rub a little pitch or resin on the flat part of the pattern for the same reason. Take a disc of metal of suitable size and grip it between the flattened end of the forme and a suitable folloAver; centre the disc by holding a piece of hard wood against it as it rotates. When true, screw up the tailstock tightly and clamp it. See that the centre is kept well oiled. Slide the rest to a convenient position and clamp it also. Take a tool, Fig. 191, and hold it to the left side of the pin in the rest, against the metal disc close to the follower. Starting from that place, slowly and very firmly press against the disc as it rotates, stroking it from near the centre to the edge again and again. Try to force it against the forme. Considerable pressure is necessary in spite of the great leverage you have against the pin. You will have no difficulty in pressing the metal in near the centre, but the rim will give you some trouble. As in raising, the most difficult part of the work consists in getting the edge to come in, and in preventing it from becoming waved or pleated. As the tool approaches the edge little pleats will begin to form, and they become largish waves at last. If you press hard the disc will just go out of shape, and buckle or wave, or even pleat badly. To prevent this you must steady the edge of the metal by holding the backstick against it. This will do something to counteract the pressure of the 
tool on the outer surface of the bowl, and it will keep the edge true. The secret of success in spinning consists in catching the pleats when and where they are small, just as they begin to rise above the surface of the metal. Press them out there. If, however, they will not disappear, and the work is getting uneven, remove it from the lathe. It has got hard ; so anneal it and then hammer it true on a stake. Whenever the work becomes hard and springy it must be annealed. When part of the metal has been spun right down on to the pattern, take the diamond-tool and turn the edge true. Be careful how you hold this tool, for if held carelessly it is liable to run in and mark your work badly. It is well ahvays to keep the edge' of the disc trued up in this way for it will spin better. When the shape is correct, slip the work off the forme and boss out the bottom with a mallet on a sandbag. It will require but little planishing. Of course, if the bottom of the bowl is not very pointed there will be no need to flatten the forme as described here. 

To lessen the friction it is necessary to lubricate the work well. Use a mixture oftallow and oil. Keep it in a covered pot and dip the tool into it from time to time. Silver and gold can be spun with oil alone, but for brass tallow is almost essential, though beeswax, or soap, is sometimes used 
instead.