How to Make Small Helical Springs

摘要

Small helical (spiral) springs used in model locomotive construction for safety-valves, axle-bxes, buffers, etc., and for many other purposes in model making, need to be correctly made if they are to function properly. If they are to be used in compression, as they mostly are, it is a mistake to close-wind them on a metal rod and afterwards stretch or pull them out to the required length. Using, that procedure, you may, by luck, produce a spring with equally-spaced coils and axially straight, but the odds are against it. A much better plan is to use a former to space the coils evenly when winding. Choose a suitable wood screw, cut off the head, and use it as a former, by gripping it in the vice or s.c. chuck and winding the wire tightly in the thread of the screw. The coils will spring back a little on being released, and a few trials with different sized screws will show the right size of screw to use to produce a spring of a definite diameter. As the working range of such springs is in most cases very small, there is no need to harden and temper them if made of hard "piano" wire, but it is important that the ends should be ground off in a plane perpendicular to the axis. Push in a match-stick (for very small springs), skewer or any bit of wood that will fit tightly inside the spring and dab the spring squarely against the side of a revolving grinding wheel. The end coil of the spring will immediately become red-hot and will be pressed down nearer to the coil below and at the same time be ground off to a tapering point. The operation is so quick that the heat has no time to travel down the spring and spoil its 'temper. Reverse on the stick and do the other end in the same way.