Milling, turning, drilling and grinding machines
The horizontal milling machine in the school workshop machines vertical and horizontal surfaces using cylindrical, disc, end and profile cutters. A cutter is a multi-tooth tool: the teeth cut in turn while the others cool. The machine table moves in three directions and the work zone is covered by a guard screen. The screw-cutting lathe is used to turn cylindrical and conical surfaces, face and part off, drill and cut threads. The cutting tool consists of a head (working part) and a shank; the shank is fixed in the tool holder. The tool-tip height depends on the job: for rough work it is set 0.5–1 mm above the centre line, for hard material 0.5–1 mm below, and for finishing level with it; the overhang must not exceed one and a half times its thickness. On a vertical drilling machine the part is clamped firmly in a vice, the bit is fixed in the chuck, and the hole centre is marked beforehand; pressure is lowered as the bit nears the bottom of the hole. A grinder is for sharpening drill bits and tools. At machines work only under the teacher’s supervision, in goggles, without gloves, with long hair tied back and no loose sleeves; the chuck key is removed before starting, the guard is down, and chips are brushed away after the machine has stopped.
Machine cards: pictures of 4 machines (milling, lathe, drill, grinder) and cards with their jobs are mixed; groups pair them and state one safety rule for each. Only the teacher demonstrates on the real machines.