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Information Please!

From The American Horologist magazine, July, 1944

Information Please
Directed by 
W. H. Samelius, Chairman 
Science of Horology and Technical Advisory Board

HRG: I have an Illinois 60 hour Bunn Special watch. Please advise if this watch should be wound every 24 or 48 hours?

Ans.- In all watches the maianspring power delivered varies throughout the running period of the watch. By designing the watch to run 60 hours, the variation of power during the first 24 hour period is less than the variation of power during the latter 24 hours so for that reason, as the mainspring delivers more constant power for the first 24 hour period, it is advisable to wind the watch each 24 hours. If you accidentally omit winding the watch after the first 24 hours, it naturally will keep running until the end of its running time, but the time piece is very likely to take a different rate during the latter part of the run, therefore, we repeat, to obtain a constant rate, it is best to wind your watch each 24 

JIT: When a watch is marked adjusted to heat and cold, 5 positions and isochronism, what is meant by isochronism?

Ans.- The word "isochronism" is derived from the Greek word meaning "equal time." As applied to a watch or timekeeping instrument, the term "Isochronism" means that the time or rate would be constant throughout the 24 hour period, that is, it will have a constant gain or a constant loss for each hour of the day. Theoretically, a balance and hairspring should oscillate at the same rate whether the arc of motion is low or high, meaning that the balance should return to center in the same length of time, regardless if the arcs are unequal during the 24 hours due to the variation of power. The resistance of the hairspring must be equal to the force of the balance. As all hairsprings are not isochronal; it is some. times necessary to test several hairsprings before one is found that will prove itself isochronal throughout the range of balance arc. The length of the hairspring has a great deal to do when striving for isochronism.

HMU: A friend informs me he always puts oil on a roller jewel? 'Is this good practice?

Answer - Oiling the roller jewel is bad practice as the oil soon turns black or will thicken or gather dust, which will soon have effects on the watch. If oiling the roller jewel was the proper thing to do, I am sure all watch factories would adopt that method, however, up to date, you will find all watches as delivered by the manufacturers, are left with the roller jewel dry.

YKG: When inserting teeth m clock wheels, is it advisable to use hard solder?

Answer - When inserting a tooth in a clock wheel, a dove tail slot is cut into the rim, a wedge filed to fit the slot and held fast by spreading or riveting the wedge to place. If hard solder· is used, the heat would take the hardness away from the teeth of the wheels when they would very likely bend over and cause trouble when the wheel is put into service. It is even advisable to avoid using soft solder when inserting teeth into clock wheels.

In the sixteenth and seventeenth centuries, an HOUR glass was standard equipment in the church, so the sermon wouldn't last too long. 

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