Modern practice is to use transparent plastic, fibre, or aluminium for T-square blades. For use in the workshop, and for 'full sizing' on sheets of plywood, a fibre bladed T-square, such as sold for school blackboard use, is ideal.
Clear plastic set squares have the advantage of the draughtsman being able to see what has already been drawn beneath them. A large adjustable set square is expensive but well worth the outlay. When buying or ordering remember that most manufacturers quote the hypotenuse of the closed set square as its size.
The same advice is given with regard to compasses. Cheap 'school' compasses are a frustrating nuisance. A large, well-engineered instrument of good quality is well worth the expense. Multiple outfits in velvet lined cases, or 'drawing sets' containing such items as ruling pens and ruling nibs for compasses are of little use in the workshop.
Circles under 2 in (50 mm) diameter are best dealt with using a circle template, the most practical being made of transparent plastic with a graded series of holes punched through them. They are accurate when used with a sharp pencil or a stylus pen and in the smallest sizes of circle are more comfortable to use than any pair of compasses.
For the drawing of curves, a set of large french curves makes a useful addition to the workshop, also a set of boat curves or railway curves which may well be picked up from junk shops. The latter are Victorian or Edwardian in origin, made of pear wood, and are frequently in well-constructed boxes. For the drawing of long sinuous or continuous curves a spline made from thin plywood, cut so that the grain of the outer skin lies across the width of the spline, is indispensable. It is a two-man job to use it.
Good quality HB or F pencils will give a thin and dark line, while a Japanese Pentel enables drawing office standard drawings to be made with a propelling pencil, the lead being half a millimetre in diameter. Should the drawing need to be reproduced, modern pencils and reprographic machines can make a very satisfactory copy without recourse to ink.
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THIS book is one of the series of Handbooks on industrial subjects being published by the Popular Mechanics Company. Like Popular Mechanics Magazine, and like the other books in this series, it is written so you can understand it. The purpose of Popular Mechanics Handbooks is to supply a growing demand for high-class, up-to-date and accurate text-books, suitable for home study as well as for class use, on all mechanical subjects. The textand illustrations, in each instance, have been prepared expressly for this series by well known experts, and revised by the editor of Popular Mechanics.