It is a simple description of the ISO 3040 taper ratio and an application to the ISO 5356.
According to ISO 3040 Geometrical product specifications
(GPS) — Dimensioning and tolerancing — Cones. The rate of taper is the ratio of the difference in the diameters of two sections of a cone to the distance between them. Like, can be seen in the figure below.
For example, in a 1:40 taper, the diameter will change 1 mm per 40 mm length.
1:40 = 0.025 = 2 * tan(alfa/2) => alfa/2 = 0.716 degree => alfa 0 1.43 degree
For example, in ISO 5356 Anaesthetic and respiratory equipment — Conical connectors — Part 1: Cones and sockets. In the table below, can be seen the different tapers for connectors sizes.
That means the alfa angle for :