Bayonet Mount

A bayonet mount (mainly as a method of mechanical attachment, as for fitting a lens to a camera) or bayonet connector (for electrical use) is a fastening mechanism consisting of a cylindrical male side with one or more radial pins, and a female receptor with matching L-shaped slot(s) and with spring(s) to keep the two parts locked together. The slots are shaped like a capital letter L with serif (a short upward segment at the end of the horizontal arm); the pin slides into the vertical arm of the L, rotates across the horizontal arm, then is pushed slightly upwards into the short vertical "serif" by the spring; the connector is no longer free to rotate unless pushed down against the spring until the pin is out of the "serif".

To couple the two parts, the pin(s) on the male are aligned with the slot(s) on the female and the two pushed together. Once the pins reach the bottom of the slot, one or both parts are rotated so that the pin slides along the horizontal arm of the L until it reaches the "serif". The spring then pushes the male connector up into the "serif" to keep the pin locked into place. A practised user can connect them quickly and, unlike screw connectors, they are not subject to cross-threading. To disconnect, the two parts are pushed together to move the pin out of the "serif" while twisting in the opposite direction than for connecting, and then pulling apart.

The strength of the joint comes from the strength of the pins and the L slots, and the spring. To disengage unintentionally, the pins must break, the sleeve into which the connector slides must be distorted or torn enough to free the pins, or the spring must fail and allow the connector to be pushed down and rotate due to, say, vibration.

It is often possible to push down the connector and rotate it, but not far enough to engage and lock; it will stay in place temporarily, but accidental disconnection is very likely.