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ln CJ13.ptcr II, full details arc given as to this necessary process, so that anyone with no knowledge of geometry, when caJled upon to make up somet;hiug, for the shop or. joh, r.a.n do so without wading through figures and formul~ in a.n endeavour to carry out. the work in hand.
• Chapter 111 deals wit.h the a.ctual cuWng 1.md fanning ‘vork, usi11g hand tool!l ; while Chapters IV a.nd V deal with t,he machines that can be used for formiug sheet metal and describe how they arc operated to get the best, result~ .. Chapter VI, which desctibes the various methodR of joining sheet metal, com].>letes this section of t he work. The final chapter clea.ls with the method of shaping sheet metal known a.~ metal ::~pinning; it is believed t hat. ibis chapter will RUppiy much-needed infornmtion concerning a !:lhoot-ruetal pr&.Rh”lR on ”hich vory lit.t.Je info rmation of a practical nature har:: hitbert.o been published.
Tjnplate is sheet iron coated with tin to protect it o,gainst rust. This is used for nearly all soldered work, as it is the eat>iest metal to join by soldering and, due to tin being the main constituent of tinma.n’s solder, the solder alloys with the tin coating and makes a neat sound joint. Tin is a safe metal to use for culinary purposes, as food is not contaminated by contact. Common tin plate~ are rolled to the required thickness, annealed, immersed in an acid bath to romovo the scale, dipped in flux. and then into a bath of molten tin which adheres to the surface.
This first tinning leaves tiny pin holes and, while thiR is not detrimental for ::~ome classes of work, the hettct• qualities receive a second dip in another bath of tin, at a lower temperature, which “floats over ” t.he pin holes left in the first coating. The highest-quality sheets used for culinary and hotel work receive a third dipping in a tin bath, thus ensuring a heavy coating of pure tin on the surface of the iron. Great care is taken to preserve the surface of these sheets, and they arc packed in boxeH interleaved with tissue paper to prevent scmtching in transit. The qualities of tinplates arfl kno•w:n a.s Common, Best, and Best Best rcspecti vely.
The sizes and thickness of tinplates are denoted by special marks, not by gauge numbers, and can be very confusing to the uninitiatcrl. Jt will be noticed that tinplate is only obtainable in fairly small sheets of light gauge. If larger or heavier sheets of tinned iron are required, the material used is known as Manchester plate or ” tinned steel,” and this may be obtained in all sizes and gaugeH in which sheet iron is obtainable. )1anchester plate is a heavily coated sheet of the highest quality, and is much used for dairy utensils, hotel work, and petrol tanks.