Modern requirements have compelled the introduction of a great variety of machine tools of all sorts, whereby the tedium of production is greatly removed, and the rapidity of manufacture increased a hundredfold. By the use of turning lathes, planing, shaping, and slotting machines, together with milling and drilling machines, a never-ending variety of articles may be produced. As such are in a manner only copying machines, the exactness of the work will greatly depend on the perfection of the tool, so that although a piece of metal is shaped into cylindrical form by the use of a turning lathe, it does not follow that it will be a true cylinder, any more than that the surface produced by a planing machine will always be perfectly straight, flat, and true. Constant care must therefore be exercised in order that the slightest error may be detected at once, and, if possible, rectified.

Too much caution when engaged with any sort of power tool in motion is impossible, and unnecessarily close proximity to gearing of all kinds should be avoided. Every machine and hand tool should be carefully and thoroughly cleaned after use, and all portable parts laid away in their respective places. Constant observation of the old maxim "A place for everything, and everything in its place" should be a law in every workshop. Breakages and accidents should be reported without delay.