Before entering upon our subject proper, we think it advisable to explain a few points, simple though they are, which might cause confusion to some readers. Our experience has shown us that as soon as we use the words “millimeter” and “degree,” perplexity is the result. “What is a millimeter?” is propounded to us very often in the course of a year; nearly every new acquaintance is interested in having the metric system of measurement, together with the fine gauges used, explained to him.

The metric system of measurement originated at the time of the French Revolution, in the latter part of the 18th century; its divisions are decimal, just the same as the system of currency we use in this country.

A meter is the ten millionth part of an arc of the meridian of Paris, drawn from the equator to the north pole; as compared with the English inch there are 39³⁷⁰⁸₁₀₀₀₀inches in a meter, and there are 25.4millimeters in an inch.

The meter is sub-divided into decimeters, centimeters and millimeters; 1,000millimeters equal one meter; the millimeter is again divided into 10ths and the 10ths into 100ths of a millimeter, which could be continued indefinitely. The ¹₁₀₀millimeter is equal to the ¹₂₅₄₀ of an inch. These are measurements with which the watchmaker is concerned. ¹₁₀₀millimeter, written .01mm., is the side shake for a balance pivot; multiply it by 2¼ and we obtain the thickness for the spring detent of a pocket chronometer, which is about the thickness of a human hair.

The metric system of measurement is used in all the watch factories of Switzerland, France, Germany, and the United States, and nearly all the lathe makers number their chucks by it, and some of them cut the leading screws on their slide rests to it.

In any modern work on horology of value, the metric system is used. Skilled horologists use it on account of its convenience. The millimeter is a unit which can be handled on the small parts of a watch, whereas the inch must always be divided on anything smaller than the plates.

Equally as fine gauges can be and are made for the inch as for the metric system, and the inch is decimally divided, but we require another decimal point to express our measurement.

Metric gauges can now be procured from the material shops; they consist of tenth measures, verniers and micrometers; the finer ones of these come from Glashutte, and are the ones mentioned by Grossmann in his essay on the lever escapement. Any workman who has once used these instruments could not be persuaded to do without them.

No one can comprehend the geometrical principles employed in escapements without a knowledge of angles and their measurements, therefore we deem it of sufficient importance to at least explain what a degree is, as we know for a fact, that young workmen especially, often fail to see how to apply it.

Every circle, no matter how large or small it may be, contains 360°; a degree is therefore the 360th part of a circle; it is divided into minutes, seconds, thirds, etc.

To measure the value of a degree of any circle, we must multiply the diameter of it by 3.1416, which gives us the circumference, and then divide it by 360. It will be seen that it depends on the size of that circle or its radius, as to the value of a degree in any actual measurement. To illustrate; a degree on the earth’s circumference measures 60 geographical miles, while measured on the circumference of an escape wheel 7.5mm. in diameter, or as they would designate it in a material shop, No.7½, it would be 7.5×3.1416÷360=.0655mm., which is equal to the breadth of an ordinary human hair; it is a degree in both cases, but the difference is very great, therefore a degree cannot be associated with any actual measurement until the radius of the circle is known. Degrees are generated from the center of the circle, and should be thought of as to ascension or direction and relative value. Circles contain four right angles of 90° each. Degrees are commonly measured by means of the protractor, although the ordinary instruments of this kind leave very much to be desired. The lines can be verified by means of the compass, which is a good practical method.

It may also be well to give an explanation of some of the terms used.

Drop equals the amount of freedom which is allowed for the action of pallets and wheel. See Z, Fig.1.

Primitive or Geometrical Diameter.—In the ratchet tooth or English wheel, the primitive and real diameter are equal; in the club tooth wheel it means across the locking corners of the teeth; in such a wheel, therefore, the primitive is less than the real diameter by the height of two impulse planes.

Lock equals the depth of locking, measured from the locking corner of the pallet at the moment the drop has occurred.

Run equals the amount of angular motion of pallets and fork to the bankings after the drop has taken place.

Total Lock equals lock plus run.

A Tangent is a line which touches a curve, but does not intersect it. AC and AD, Figs. 2 and 3, are tangents to the primitive circle GH at the points of intersection of EB, AC, and GH and FB, AD and GH.

Impulse Angle equals the angular connection of the impulse or ruby pin with the lever fork; or in other words, of the balance with the escapement.

Impulse Radius.—From the face of the impulse jewel to the center of motion, which is in the balance staff, most writers assume the impulse angle and radius to be equal, and it is true that they must conform with one another. We have made a radical change in the radius and one which does not affect the angle. We shall prove this in due time, and also that the wider the impulse pin the greater must the impulse radius be, although the angle will remain unchanged.

Right here we wish to put in a word of advice to all young men, and that is to learn to draw. No one can be a thorough watchmaker unless he can draw, because he cannot comprehend his trade unless he can do so.

We know what it has done for us, and we have noticed the same results with others, therefore we speak from personal experience. Attend night schools and mechanic’s institutes and improve yourselves.

The young workmen of Toronto have a great advantage in the Toronto Technical School, but we are sorry to see that out of some 600 students, only five watchmakers attended last year. We can account for the majority of them, so it would seem as if the young men of the trade were not much interested, or thought they could not apply the knowledge to be gained there. This is a great mistake; we might almost say that knowledge of any kind can be applied to horology. The young men who take up these studies, will see the great advantage of them later on; one workman will labor intelligently and the other do blind “guess” work.

We are now about to enter upon our subject and deem it well to say, we have endeavored to make it as plain as possible. It is a deep subject and is difficult to treat lightly; we will treat it in our own way, paying special attention to all these points which bothered us during the many years of painstaking study which we gave to the subject. We especially endeavor to point out how theory can be applied to practice; while we cannot expect that everyone will understand the subject without study, we think we have made it comparatively easy of comprehension.

We will give our method of drafting the escapement, which happens in some respects to differ from others. We believe in making a drawing which we can reproduce in a watch.