The following remarks refer in the main to foreign watches with a Lepine movement.
Rotate the wheels connecting the hour and minute hands by the aid of a key; a glance will suffice to show whether the several depths, which should be light, are satisfactory. The wheels should not rub against one another, the plate, barrel, or stopwork. The barrel should have been previously examined to ascertain that it was not inclined to one side, as, if it were, an error would probably be made in estimating the degree of freedom. The set - hands arbor (the square of which should be a trifle smaller than that of the barrel arbor) must turn rather stiffly in the centre pinion, and the cannon pinion must be held on the arbor sufficiently tight to avoid all chance of its rising and becoming loose; for this would alter the play of the hands and motion work. Any fault found in the adjustment should be corrected at once, to avoid doing so after the movement has been cleaned. Slightly round the lower end of the cannon pinion and the steel shield, taking care to avoid forming a burr on the pinion leaves.
There must be sufficient clearance between the plate and barrel; the barrel and centre wheel; the several wheels in succession, both between themselves, their cocks, and sinks; between the balance on the one hand and its cock, the centre wheel, fourth-wheel cock, the balance-spring coils and stud on the other. The fourth wheel is frequently found to pass too near to the jewel forming the lower pivot-hole of the escape wheel. End-shake of the wheels may be tested by taking hold of an arm of each with tweezers and lifting it. This may also be done in the case of the escape wheel, but, when the cock is slight, it will be sufficient to press gently upon it with a pegwood stick, then releasing it, and observing the apparent increase in the length of pivot. At the same time, ascertain that the width and height of the passage in the cock are enough to allow the teeth, when carrying oil, to pass with the requisite freedom. Holding the watch on a level with the eye, lightly raise the balance with a pegwood point several times, each time allowing it to fall.
The variation observed in the space between the collet and cock will indicate the end-shake of the balance staff.
Side play of the balance pivots in their holes can be easily estimated by touch, or by the eye, attentively watching the upper pivot through the end-stone with a powerful glass, while the watch lies flat, and the lower pivot in the same manner with the watch inverted. If the endstones are not clear enough, which is rare, first remove one endstone and examine the pivot; then replace it and remove the other. It should be possible to rotate the balance until the banking pin comes against its stop, without causing the escape wheel to recoil at all, or allowing a tooth to catch outside the cylinder behind the small lip. The banking pin sometimes passes too near to the fourth-wheel staff. The U-arms should rest as nearly as possible in the middle of the banking slot of the cylinder; that is to say, they should be as far from the upper as from the under edge of this slot, so that the end-shakes may have free play in all positions of the watch. See that the balance spring is flat; that it coils and uncoils regularly without constraint; that it does not touch the centre wheel, the stud, or the inner curb-pin (with its second coil).
The rapid examination of the escapement may now be regarded as complete, if the watch in hand is merely being cleaned after having previously gone well. But if a watch that has not gone well previously, or if a new one, the action of the escapement must be thoroughly tested.
The train being in motion through the force of the mainspring or the pressure of a finger against the barrel teeth, examine with a glass all the depths that are visible. That of the escapement, for example, can be easily seen through the jewelled pivot-hole when this is flat, the watch being laid horizontal and a powerful glass used. When the action cannot be seen in this manner with sufficient distinctness, hold the watch up against the light and look through it. Depths that cannot be clearly seen, or about which any doubt exists, must be subsequently verified by touch. With a new watch, it may be found necessary to form inclined notches at the edge of the cocks or near the centre hole of the plate, so as to see the action of the depths. But it is important that the settings of the jewels are not disturbed, and indeed that enough metal is left round these holes to admit of their being re-bushed if necessary.
Invisible and doubtful depths must be tested by touch, and the requisite corrections applied after having re-polished the pivots, etc, as may be necessary. Holes a trifle large are less inconvenient than those which afford too little play, providing the depths are in good condition.
Remove the endstone from the chariot, and see that the pivot projects enough beyond the pivot hole when the plate is inverted. Remove the cock and detach it from the balance. Take off the balance spring with its collet from this latter, and place it on the cock inverted, so as to see whether the collet is central when the outer coil is midway between the curb pins. Remove the cock endstone and endstone cap, place the top balance pivot in its hole, and see that it projects a little beyond the pivot hole. Put the balance into the "figure 8" calliper to test its truth, and, at the same time, to see that it is sufficiently in poise; remember, how* ever, that the balance is sometimes put out of poise intentionally.
Let the train run down: if it does so nosily or by jerks, it may be assumed that some of the depths are bad, in consequence of the teeth being badly formed, the holes too large, etc. To test the latter point, cause the wheels to revolve alternately in opposite directions by applying the finger to the barrel or centre-wheel teeth, at the same time noting the movement of each pivot in turn in its hole; a little practice, comparing several watches together, will soon enable the workman to judge whether the play is correct. The running down of the train will also indicate whether any pivots are bent.