Now, if the pinion is put in the centres and tried, it will probably be found to have warped a little in hardening. This is corrected in the following manner: The rounding side of the arbor is laid on a soft iron stake, and the hollow side is stretched by a series of light blows with the pane of the hammer, given at regular intervals along the curve. Having got the leaves to run quite true by this means, turn both arbors true, and polish them with the double sticks - these are simply 2 pieces of thin boxwood, about $ in. wide and 3 in. long, fastened together at one extremity and open at the other; between these the arbor is pinched with oil and fine emery, and they are traversed from end to end, to take out the graver marks. The brass for the collet, to which the wheel is riveted, is now drilled, broached, and turned roughly to shape on an arbor. The position on the pinion arbor is marked with a fine nick, and the collet is soldered on with soft solder and a spirit lamp, taking care not to draw the temper of the arbor when doing so. Wash it out in soda and water, and polish the arbors with crocus, turn the collet true, and fit the wheel on.
If the pinion face is to be polished, it is now done, the facing tool being a piece of iron about -1/16- in. thick, with a slit in it to fit over the arbor with slight freedom, and using oil-stone dust first, and then sharp red stuff.
Generally, cut pinions are used for the centres, and in this case the body of the arbor is sufficiently large to allow the front pivot to be made from the solid arbor; but in some movements, particularly those used for spring dials, the centre pinions are made from pinion wire in the manner just described; but for the front pivot a hollow tube of hardened and tempered steel is soldered on to the arbor. This piece should always project sufficiently far through the pivot hole to allow it to be squared to receive the friction spring which carries the motion work. In cases where this pivot is much cut, it is best to remove this piece and substitute a new one, and as these pinions are very long and flexible, some difficulty will be experienced in turning this pivot unless some form of backstay is used to support the arbor, and prevent it springing from the graver.
In common clocks, where both third and escape pinions are worn by the wheel teeth, if the pivots are still in good condition, and the expense of new pinions is objected to, very good results can be obtained by the following alteration. The third pinion leaves must be turned back from the outer end rather more than the thickness of the centre wheel, the pivot shoulder also turned back the same distance, the pivot remade, burnished, and shortened. Then the pivot hole in the front plate is carefully opened with a broach to about twice its original size, and a stopping with a good large shoulder is turned true on an arbor and riveted into the plate. The thickness of the shoulder of this stopping will depend on the amount that you have shortened the arbor, and must be such as just to give correct end-shake to the pinion. By shifting the third wheel and its pinion thus, a fresh portion of both the third and escape pinions is brought into action, and as good results will be obtained as by putting 2 new pinions, with a very small expenditure of time and trouble.
One often finds in old clocks that the escape wheel is so much out of truth that anything like close scaping is out of the question, as so much drop has to be given to enable some teeth to escape, that nearly all the power is lost; in such a case a new wheel is a necessity, and if you want to get a good hard wheel you must make the blank yourself. Take a piece of hard sheet brass, about twice as thick as the wheel is to be when finished, and cut from it a square sufficiently large for your wheel; then with a hammer with a slightly rounded face, reduce it to nearly the thickness you require. In hammering, go regularly over the surface, so that no 2 consecutive blows fall on the same spot; and when one side is done, turn it over, and treat the other in the same way. File one side flat, find the centre, and drill a hole nearly as large as required for the collet; cement it with shellac to a flat-faced chuck in the lathe, and centre it true by the centre hole. Mark with the graver the size of the wheel, and with a narrow cutter remove the corners; face the blank with the graver, and turn it to size, leaving it slightly larger than the old wheel; knock it off the chuck and reverse it, bringing the turned face next the chuck, turn that face flat and to thickness, and it is ready for cutting.
After it is cut, remove any burrs with a fine file, and mark a circle to show the thickness of the rim, and on that circle divide it into the number of arms it is to have; mark also a smaller circle slightly larger than the collet on which it is to be riveted, draw lines through the divisions in the outer circle and the centre of wheel to mark the centre of the arms. Drill a hole beat tween each 2 arms to enable you to enter the file, which to begin with should be a coarse round one, then follow with the crossing file, holding the wheel between a piece of thick card in the vice; finish by draw-filing the arms and crosses with a very smooth file, followed by a half-round scraper used as when draw-filing. This leaves the surface smooth and ready for the burnisher, of which tool two different shapes will be required, one oval, and the other half-round. These tools, when in use, require to be repeatedly cleaned on a piece of leather, and passed over the palm of the hand, to prevent tearing up the surface of the metal.
The wheel teeth are now polished out with a short-haired brush and fine crocus and oil; then take out the file marks from both sides of the wheel with water-of-Ayr stone and oil, and it is ready for riveting on.
The riveting stake for clockwork is exactly like the ordinary pinion riveting stake used by watchmakers, only it is in 2 pieces dividing down the centre of the holes; if it were in one piece, the pinion head would prevent it passing through a hole of the proper size to fit the collet; it has 2 steady pins to ensure its coming together properly. Take a slight chamfer out of the front of the wheel hole, and roughen the surface of it with a graver, turn the collet down to fit in tightly, and rivet it on with a half-round punch, taking care to strike light blows and keep the wheel turning while riveting. It is then ready for stoning off and polishing with a flat wood polisher and fine crocus and oil. In crossing out a small delicate wheel, it is a good plan to fasten it with shellac to a flat plate of brass, having a hole in it rather larger than the inside of the rim of the wheel. In this way all danger of bending a tooth of the wheel accidentally is avoided, and the crossing can be finished without removing it from the plate.