E14 shares the screw principle with E27 at roughly half the diameter, and the tolerance band scales down with it. The absolute allowance on thread form is therefore smaller in micrometres, which means the same amount of gauge wear that is harmless on an E27 member can push an E14 member out of tolerance.
Wear is a loss of material at the flanks and crests of the thread, and its absolute magnitude depends on how often the gauge is used rather than on its size. A shop that gauges ten thousand E14 caps a month will wear out an E14 thread gauge in the same calendar time it takes to wear an E27 gauge used at the same rate, but the E14 gauge reaches its tolerance limit after removing far less material. Recalibration intervals for small caps should therefore be shorter, not the same.
Small gauges get dropped and get carried loose in a pocket. A single burr on the go member will scratch the cap thread and can make a good cap fail, and a flattened crest on the no-go member will let a bad cap through. Inspect the gauge visually under low magnification before each shift; it takes seconds and catches most of the damage.
As with E27, the dimensional set is not enough. E14 lamps are often used in small decorative fittings where the holder is short, so a contact-making check against a reference holder is the fastest way to catch a batch of caps whose centre contact sits a fraction too deep.
