Reed Relays and
Electronics India Limited
Manufacturer of Reed Switches, Reed Sensors and Reed-based products
Reed Relays and Electronics India Limited Incorporated in 1971

Reed Switch Lead Formation Dimensions

Some rules apply to cropping and forming of Reed Switches. Stops or guides that use the end of the seal as a reference point for forming can damage the hermetic seals and this is why it is better for the Reed Switch manufacturer to crop or form leads.

Using the seal as a dimensional reference point invariably results in variation of the lead dimensions after forming. The recommended practice is to use the lead ends as a reference, providing clamping between the seal and the forming point.

A clamping device protects the seals from the stress that comes from formation. This approach also allows for normal variations in glass length and distance between seal and each lead end.

Requesting for formations

When requesting for reed switches with cropped or formed leads, it is important to note some points regarding dimensions and tolerances. Illustrated are two methods for drawing up dimensions for the same goal-post modification.

Wrong Reed Switch dimensioning
Reed Switch dimensions (illustration 1)

This first illustration presents an impossible situation mainly because the glass length and its position relative to the gap vary greatly between reed switches. Compared to the precise dimensions of the reeds, it is not advisable to use the sealed glass length as a reference point. It is also better to now stack three dimensions to come up with an overall length, as this would not be achievable.

Correct Reed Switch dimensioning
Reed Switch dimensions (illustration 2)

The better way to assign dimensions and tolerances to a cropped or formed reed second is explained here. The illustration 2 on the left has all the necessary dimensions referenced either from the air gap or the reed, both of which can be held with close tolerances. The bends are set up equally from the magnetic center of the reed switch, which is located at the air gap, where the blades overlap. When a magnet is used for actuation, the operating point for reed switches with the same Operate AT will be uniform. Requesting for a formed reed switch with such dimensions can have leads cut and formed in one operation, and the number of measurements required to inspect the modified switch is minimized.