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Fitting New Cylinder and Plugs

In most cases of broken cylinders the upper half is left while the lower and most important part is missing. Take total length over all first, the same as in replacing staff, which can be done by the use of the Staff Length Gauge, and then measure the length of the old cylinder from the under side of the hub to the end of the top pivot, and the difference between the two measurements will give the length of the lower part of cylinder and pivot, and this will serve as a guide in selecting an unfinished cylinder of proper length. The cylinders and also cylinder plugs can be purchased from material houses. Having selected a cylinder, proceed to center it in the lathe in a finely centered chuck, leaving lower end exposed. Turn the lower pivot first; then finish off the lower plug, and if necessary, turn off any surplus body of shell from the lower part of the cylinder as occasion demands. For obtaining the requisite measurements for the work, the little tool shown in Fig. 19 and the Staff or Cylinder Height Gauge shown under Gauges will be found useful. Saunier advocates the use of experimental cylinders, and suggests that the workman will do well to make two or three different sizes during his leisure moments. They can be made from the cylinders kept in stock by material dealers. The cylinder and lower plug are better to be in one piece to increase the strength; the slot shallow and in different positions, (for the position of the banking slot is the most difficult to ascertain), and the cylinder only perforated where the top plug is inserted. The top plug should be removed, the hole tapped, and a new plug, somewhat longer, screwed in. The action of this tool is similar to the Staff Height Gauge mentioned above.

After the lower end is finished the wax is turned away and the cylinder turned true and finally cut off at the proper length, preserving as fine a center as possible, after which the cylinder is reversed and finished. In pivoting, it is very seldom necessary to drill the cylinder, as the upper and lower pivots are generally the extremity of plugs closely fitting in each end. In most cases the top pivot may be replaced by resting the cylinder on a stake, the hold of which is of a sufficient diameter to allow of the entrance of the plug, and too small to allow the cylinder to pass through. A knee punch and a few light taps of a hammer are generally sufficient to drive the plug out far enough to admit of the turning of a new pivot. The lower plug must be driven out entirely (being too short to admit of turning a new pivot) and a new plug inserted. The plugs must be made to fit tightly without taper, as with a taper plug there is great danger of splitting the cylinder. Should the plug be very tight and difficulty is encountered in driving it out, a few light taps all around the cylinder will generally stretch it enough to remove the plug easily.