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Watchmakers' Hand Book

Part II,
MATERIALS EMPLOYED IN HOROLOGY
Page 15

POLISHING.

      181. To polish brass. When it is required that a surface be maintained perfectly flat, first dress with somewhat coarse water of Ayr with blue stone and then go over with a softer stone. Next work with fine rottenstone and oil on a felt or buffstick for objects of large dimensions and on a piece of pegwood for smaller articles. They are then soaped, washed and dried in sawdust (151).

      The work can be accomplished more rapidly, but without maintaining a perfectly flat surface, by first employing pumice-stone and oil spread over a large piece of soft wood or felt. It is then cleaned and polished with rottenstone.

      When the form permits of it, a tin disc charged with tripoli and rotating in a lathe can be employed.

      Observations. Pumice-stone is powdered fine and then sifted. In using rottenstone a piece an inch or two cube is crushed between the fingers into a cup of water, and this is decanted so as to give several degrees of fineness (168). The polishing can best be effected by using old wood from which the sap has dried up: French chalk has but little action if the polisher with which it is applied is from the animal kingdom, horn for example, etc.

      182. To polish watch wheels. Although the operation of polishing is extremely simple, it is very important that a certain degree of manual skill be acquired by practice, as otherwise the work is never of the best.

      We will here enumerate several methods of procedure, in order that, after trial, each can select the method with which he finds himself most successful.

      Smoothing. The smoothing should be done carefully with very soft water of Ayr stone, free from veins and hard grains and perfectly flat. The wheel must then be well cleaned.

      Polishing. In polishing, rods of walnut or boxwood, of tin, bronze or zinc are used. A buffstick and burnisher are also employed.

      The materials applicable are rottenstone (with oil or alcohol, being made very thin in the latter case) tripoli, prepared chalk, polishing rouge, crocus, etc. These materials have been sufficiently described in articles 165--7. Workmen sometimes prefer to make mixtures of two or more substances, but it is more usual to employ them separately.

      183. First Method. After smoothing and cleaning the wheel, it is polished while resting on a piece or cork, where it is held between the fingers which cause it to rotate; the best rottenstone is used and is applied by smooth pieces of boxwood, about 8 inches long, which are filed to a bevel edge. It is best to have the grain of the wood crosswise and the polishers should be of sufficient thickness to prevent their bending when in use.

      The rottenstone can be replaced by tripoli and the boxwood by walnut. Some wheel polishers prefer a triangular stick of pure tin or zinc which is often planed to ensure perfect flatness; rouge, rottenstone or tripoli can be used with it.

      The wheel, after being well washed in soap and hot water, is throughly dried and finished with a fine buffstick in good condition, while it rests on a cork covered with smooth felt; this operation is with a view to prepare the surface prior to using the burnisher.

      Some polishers, instead of the dry buffstick, prefer one charged with a little rouge, tripoli or rottenstone moistened. But such preparations must be applied very sparingly as they involve a risk of rounding the edges.

      The burnisher is next rapidly passed over the surface of the wheel, which rests on cork, covered with a linen rag, or on a piece of wood, covered with smooth paper. Some give long backward and forward strokes with the tool; others give semi-circular movements. It will be found sufficient to give short strokes from half an inch to an inch in length. A slight motion of the wrist is all that is required and after a few trials the necessary skill will be attained. We cannot say more. Practice must also be relied on for determining the most suitable pressure.

      The burnisher, about half an inch wide and four inches long, is curved in the direction of its length. A straight burnisher might be used, but is is less safe; the angle of the burnisher set against the pinion should be rounded off.

      The burnisher is cleaned and restored by drawing across a large flat piece of walnut charged with rouge of very good quality and very pure. After being washed, a little white wax is passed over it, and then it is again rubbed vigorously with a piece of cloth or a buffstick; finally with a soft linen rag. When a tendency to stick shows itself this operation must be repeated.

      184. Second process. By this method the surfaces are somewhat rounded off at the edges. But, although not so pleasing to the eye, this circumstance involves no inconvenience except that, when burnishing, the burnisher would not at once come in contact with the entire surface; we need not, however employ the burnisher.

      Laying the wheel on a cork, some workmen smooth the wheel by covering it with oil and fine tripoli and rubbing with a walnut-wood stick. Others spread a layer of such a mixture first on the stick and then rub the wheel. When no more lines are observable across the surface of the wheel it is cleaned, placed on a fresh cork that is covered with a soft linen rag, and polished with a fresh buffstick (or one that has already been used for a similar purpose) and an abundant supply of rouge or even fine rottenstone and oil may be used. The buffstick receives a semi-circular movement in all directions in order not to needlessly round the corners, the edges of the teeth and the crossings.

      It is then washed in warm water, bathed in alcohol and dried with a fine linen rag.

      185. Third process. After smoothing with a very soft stone, rub it with a piece of the root of boxwood cut across the fibre, on which is a layer of the following composition:

      Two-thirds rottenstone mixed with one-third castile soap, worked into a paste with a few drops of water so that, although not a liquid, it can be spread out at will.

      Make the wheel move backwards and forwards between the fingers while resting on a smooth, good cork, without a linen rag, and, as the operation nears its completion, a semi-circular motion should be given to the wood. Wash with soap, boil in alcohol and dry.

      The wheel can be burnished on a cork without any linen rag and the (curved) burnisher should be moved with short circular strokes from the center towards the circumference, gradually working up towards the extremity of the burnisher; the same portion of the burnisher should not pass twice over the wheel (see also article 166). For common work, fairly satisfactory results may be obtained by using French chalk and a piece of hard wood.

      Clock wheels are polished with a piece of felt and rottenstone. They are subsequently soaped, washed and dried in sawdust. (151)

      186. To polish lever escape-wheel teeth. The Lancashire escape-wheel makers employ a triangular frame carrying at its corners, (1) a cutter to slit the teeth, (2) a cutter to shape them, and (3) a revolving piece of hard leather of a section corresponding to the form of the space. This latter is charged with the finest glossing stuff, used dry, and the sides of the teeth of six wheels at a time are polished by revolving the disc in each of the spaces in turn. It is hardly necessary to observe that the operation is completed before the wheels are removed from the cutting engine.

      187. To polish sinks or oil-cups. A piece of pegwood, rounded at the end, is used for this purpose, rotating it in a lathe; the watch plate or cock should be inclined in varying directions to the stick in order to remove scratches. If a very high polish is required it may be given by following with a stick, the end of which is covered with wash-leather charged with rouge.

TO POLISH STEEL.

      188. The polishing must always be preceded by a very thorough smoothing, either with oilstone dust, fine emery, or coarse rouge. If any lines are left to be erased by means of fine rouge, the operation becomes tedious and is rarely successful. The oilstone dust is applied on an iron or copper polisher. When it is desired to preserve the angles sharp, at a shoulder for example, the polisher should be of steel.

      When using diamantine an iron polisher, drawn out and flattened with a hammer, answers very well.

      With fine rouge, a bronze or bell-metal polisher is preferable for shoulders; and, for flat surfaces, discs or large zinc or tin polishers, although glass is preferable to either of these.

      After each operation with oilstone dust, coarse rouge, etc., the polisher, cork, etc., must be changed, and the object should be well cleaned--preferably by soaping; perfect cleanliness is essential to success.

      Fine rouge or diamantine should be made into a thick paste with oil; a little is then taken on the polisher or glass and worked until quite dry. As the object is thus not smeared over, a black polish is more readily obtained, and the process gets on better if the surface is cleaned from time to time.

      189. To get a good black polish. As just pointed out, this is mainly secured by using very little polishing material at once, in a very little liquid on either, the polisher or glass plate and drying up quickly. If the surface does not prove satisfactory at first, it will often be found that a final rapid and light application of dry diamantine or rouge on a piece of glass or pith will produce a brilliant black polish.

      If operating on an axis or staff, polish as well as possible, first erasing the marks of the graver or file, and then, hold the ferrule between the fingers, rotate it with one hand and with the other rub the axis lengthwise with a pegwood stick charged with rouge or diamantine.

      A rod will show a black polish if it be rubbed lengthwise with emery paper of gradually increasing fineness, oil being applied with the finest quality.

      To polish flat surfaces. Place the object on a sound piece of cork covered with a clean rag and rub with a long strip of ground glass.

      To polish a square shoulder. Fix a rod in place of the T-rest of the turns, and set it in such a position that the polisher rests on this vertical rod when lying flat against the shoulder. Another and better method consists in cementing or otherwise fixing in the plane of the shoulder a brass disc of such dimensions that the polisher is constrained to remain flat.

      Observations. The corner of the polisher that is used for polishing a shoulder should be neither right-angled nor too acute. In the first case it would round off the shoulder, and in the second it would become soon distorted and leave dull radial marks on the surface.

      Diamantine should not be used for polishing the acting surfaces of pivots, the pallets of escapments, etc., since this material, as well as emery, is liable to leave particles embedded in the steel which occasion rapid wear.

Submitted by: Samuel Kirk (##)

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