Appendix to Part 245

Set forth in this appendix are the thickness tolerances, and tests referred to in the foregoing Guides in this part.

1. Thickness tolerances: plated and electroplated cases. The minimum thicknesses specified in paragraphs (d), (e), and (f) of § 245.3 for the coatings of gold or gold alloy on watchcases shall mean that the coating of precious metal affixed to the surface of the metal stock shall be throughout the surface and at the thinnest point not less than the thickness specified after the completion of all finishing operations, including polishing, except, however, for such deviations therefrom, not exceeding 20 percent (minus) of the stated thickness, as may be proved by the manufacturer to have resulted from unavoidable variations in manufacturing processes and despite the exercise of due care, which deviation so proved shall be allowed if and when the quantity of precious metal remaining plated on the outside of the case is sufficient to equal the quantity necessary to provide the specified minimum thickness at all points on such watchcase including the thinnest point.

2. Gold electroplate: standards and tests. The gold electroplated surface coating of a watchcase should be free of cracks, blisters, pits or other flaws, and capable of successfully undergoing the following tests:

a. Adhesion. The watchcase should be heated to a temperature of not less than 360° nor more than 400 °C. and maintained at that temperature for not less than 5 minutes. At the end of that time such surface coating should show no signs of blistering, flaking, peeling, or similar defects.

b. Hardness. Such surface coating should undergo a Knoop hardness test with a 25 gram load and achieve a rating of not less than 130.

c. Porosity. After such surface coating has been thoroughly cleaned and freed of any foreign material, the case should be:

(1) Immersed in a solution of one part concentrated nitric acid (sp.gr. 1.42) and one part water at room temperature for 5 minutes; and

(2) Exposed to fumes of concentrated nitric acid (sp.gr. 1.42) in a closed vessel for 3 hours at room temperature.

At the conclusion of each of the foregoing porosity tests, the surface coating should show no signs of having been attacked. Any discoloration or pitting should be considered as signs of an attack. The nitric acid solution in which the watchcase was immersed should be tested for the presence of metal by making it slightly alkaline with ammonium hydroxide and by adding a solution of ammonium or sodium sulfide. The formation of a black precipitate indicates that the coating has been attacked.

3. Test for shock resistance. A watch should be tested for shock resistance in a room having a temperature between 18° and 25 °C. which does not vary by more than 2° during the test. A wrist watch which does not have a permanently affixed band should be tested without the band or strap.

The test should be conducted as follows:

a. One hour after the watch has been fully wound, its daily rate in each of the following three positions should be determined by observing it for 2 minutes in each position:

(1) Position HB (horizontal with the dial facing down);

(2) Position VC (vertical with 3 o'clock to the watch's left);

(3) Position VB (vertical with 3 o'clock pointed downwards).

b. Shocks equal to that which the watch would receive if it were dropped from a height of 3 feet onto a horizontal hardwood surface should be applied as follows:

(1) The first shock should be applied to the middle of the watch at a position directly opposite the crown and in a direction which is parallel to the plane of the watch;

(2) The second shock should be applied to the crystal, and in a direction which is perpendicular to the plane of the watch.

c. Five minutes after the last shock, the daily rate of the watch in each of the three positions described in a. above should be determined by observing it for 2 minutes in each position. The differences in daily rate before and after the shock should be determined for each position. The residual effect of the shocks will be equal to the greatest of these differences.

A watch will be considered to have passed the foregoing test, if after application of the shocks, it does not stop; the residual effect does not exceed 60 seconds per day; and an examination of the watch does not disclose any physical damage which would affect its operation or appearance, e.g., hands bent or out of position, cracked crystal, or automatic or calendar devices inoperable or out of alignment.

4. Test for water resistance. A watch should be tested for water resistance by immersing it completely for at least 5 minutes in water under atmospheric pressure of 15 pounds per square inch and for at least another 5 minutes in water under an additional pressure of at least 35 pounds per square inch (total pressure of 50 pounds per square inch). If the watch does not admit any water or moisture it will be considered to have passed the test.

5. Test for antimagnetic qualities. A watch should be tested for its resistance to magnetism by placing it in a demagnetized condition in an electrical field of not less than 60 Gauss for at least 5 seconds in a vertical position and for at least 5 seconds in a horizontal position. If the daily rate of the watch has not been changed by more than 15 seconds as a result of the foregoing exposure, it shall be considered to have passed the test.