The same standard covers whether a lamp fits and whether it is safe, and because both live in one document, buyers often treat a dimensional test report as evidence of safety. It is not. The two sets of requirements use different test methods, different equipment and different acceptance criteria.
Gauges, contact-making checks and torque tests establish that the cap will mate with holders made to the standard, that electrical contact will be made, and that the mechanical joint will survive normal handling. They say nothing about insulation, leakage, or temperature.
Insulation resistance, dielectric strength, creepage and clearance distances, cap temperature rise and mechanical strength after thermal cycling are tested with electrical and thermal equipment. A cap that fails dielectric strength can be dimensionally perfect, and a cap that passes every electrical test can be impossible to insert.
When a supplier sends a compliance certificate, read which clauses it covers. A report covering only dimensional clauses is a useful incoming inspection tool and a useless safety document. Buying on that basis and then discovering the gap during a retail audit is the most expensive way to learn the difference.
