Tin & Terne Plate

Tin and terne plates are made of soft steel or iron sheets coated on both sides with tin or a mixture of tin and lead. When pure tin is used for coating, the plates are known as bright tin plates. For roofing purposes, the plates are coated usually with a mixture of tin and lead. Such plates are known to the trade as terne plates but are commonly called tin, or tin plate. Terne plates are coated with mixtures varying from 2 parts tin and 3 parts lead to 1 part tin and 4 parts lead. The weight of the coating varies from 8 to 60 pounds to the standard box, which consists of 112 plates 20 inches by 28 inches in size. The weight of the coating is independent of the proportions of tin and lead in the coating.

Gauge

Gauge denotes the weight and approximate thickness of the sheets to which the coating is applied. The gauges commonly used for roofing are No. 30 U. S. Standard Gauge (see Table II) having a weight of 8 ounces to the square foot, and No. 28 gauge, weighing 10 ounces to the square foot. These weights of sheets are known by the letters IC for the No. 30 gauge, and IX for the No. 28 gauge. The gauge of the sheet has no relation to the weight of the coating which is applied to it. IC plates are used for the main part of the roof. The IX plates are used for gutters, valleys, conductors, flashings, and similar work, and should be heavily coated.

The size of the plates is marked on the boxes in which they are shipped. The common sizes for roofing are 14 inches by 20 inches, and 20 inches by 28 inches. The box is also marked with the weight of the coating. Thus, a typical marking is "CHARCOAL IC 20X28-40," the word charcoal referring to the brand or grade, the IC to the weight of the steel or iron sheet, and the 40 meaning that 40 pounds of the mixture of tin and lead was applied to the box of 112 plates 20 by 28 inches in size. Perfect plates are stamped usually with the brand, gauge, and weight of the coating, and are called primes. Imperfect plates are called wasters, and are not stamped. Brands are the different marks or devices used by tin-plate makers to identify their products. Reliable manufacturers always endeavor to maintain a uniform merit in the different brands which they turn out. The best grades of roofing plates always have the brand stamped on the plate, as well as the weight of the sheet and the weight of the coating. For roofing purposes, it is well for the architect to specify a brand of tin that has a reputation for durability.

Soldering

Soldering is the process of joining two metal surfaces together by means of solder. Soldering is done by means of a copper bit, sometimes called a soldering copper or soldering iron. The edges of surfaces to be joined are cleaned and coated with a flux, such as powdered rosin. The copper bit, heated above the melting point of the solder, is cleaned and dipped in the flux. A bar of solder is then held against the end of the bit so that the solder will melt and run into the joint. The hot bit is rubbed back and forth along the joint, to keep the solder liquid, and to guide it into the joint. The solder unites the surfaces of the metal rooting, and forms a solid, metal, water-tight joint. Copper bits weigh from 2 to 8 pounds to the pair, and are used in pairs, one bit being heated while the other is in use. Practically all roof soldering is done by this method.

Solders

Solders are mixtures of two or more metals. When melted, solder adheres strongly to the clean surfaces of certain other metals, and is used to fasten such surfaces together. The solder used for tin roofing consists of tin and lead, the usual proportions being equal parts of each. For this reason the solder is sometimes referred to as halfand-half solder. This solder has a melting point of about 370° Fahrenheit.

Fluxes.

Fluxes are used to aid the melting of solder, and to clean the surfaces of metals to be joined. The fluxes commonly used, and the Metals to which they are applied are given in Table III.