Need help w/ home made contact points (electrical)

[5ubtle]

I am looking to manufacture my own replacement piece for a set of electrical contacts. One of the leaf springs fatigued after 21 years. I have considered bridging the break in the leaf, but I would prefer to recreate the whole thing. I think that ideally, I would like to get some "relay contact spring" material that is the width of a single leaf, make 2 leaves, and mechanically bond them together at the pivot point. I believe that the material may be "beryllium copper".

Anybody here willing to admit that they have experience with something similar? Can you give me some pointers on were to get material? I have found some on eBay, but its in Argentina. It would be good if I could find a closer supplier and a smaller quantity.

The leaf material is 0.4 mm thick.

 

[RPH]

I work with induction equipment and beryllium copper is used quite often. The one thing I know for sure is that it’s dangerous for the machinists. They have to use extra safety gear and extra caution with it. But that being said they get the material Copper and Brass sales.
They have been bought out though. This should help with your search.
https://www.thyssenkrupp-materials-na.com/materials/copper/

 

[rlitman]

Beryllium copper is used in all sorts of things. Most commonly in the finger strips used to shield electronic cases from radio interference.

It's rather dangerous if you grind it, as you don't want to inhale any dust, but it's safe enough to punch cut and bend.

How do you plan to make the contacts? That's a different alloy.

0.4mm BeCu is going to be expensive. Can you work around this in a different way, without trying to re-make the spring?

 

[kd3pc]

regular spring steel will hold up for a decade or so. and no risk in using beyond the usual warnings.

should be available on the net in small dimensions.

 

[zeke67]

Worked at a place that had a door buzzer on the entry door. The sort of buzzer on old homes, before door bells became common. Door open, buzzer buzzed. We'd replace that thing a couple times each year because the contacts would burn out. We jury rigged a set of car points. The sound was different. Sharper with a flat tonal quality. But that thing lasted for several years.

 

[5ubtle]

Thanks to all for the informative replies. I was not aware of the dangers of beryllium copper dust. Now that I am, I would rather stay away from it if I can. As I understand it, beryllium copper is used in this application because it has a very high tensile strength (>200ksi depending on tempering for C17200). I wonder if I can get away with a more commonly available material like "cartridge brass" (C26000) with an tensile strength around 70ksi. I have found that I can get 0.4mm brass strips from the hobby shop. I wouldn't mind if I had to remake the contacts every 5 years or so. I like the idea of brass over spring steel because I would like to solder it to the circuit board.

I was able to bridge the broken leaf for a temporary fix, but with the shortened effective spring length, it is sure to fail again soon.

 

[rlitman]

...As I understand it, beryllium copper is used in this application because it has a very high tensile strength (>200ksi depending on tempering for C17200). I wonder if I can get away with a more commonly available material like "cartridge brass" (C26000) with an tensile strength around 70ksi...

Sorry, but probably not. It isn't the tensile strength, but the elasticity that is important. Brass may rapidly work harden and crack when used as a spring, though some brass alloys make better springs than others. A steel spring might work, but will necessarily have a higher electrical resistance (partly because of a lower conductivity, and partly because it will be thinner too).

 

[5ubtle]

It isn't the tensile strength, but the elasticity that is important.

Is there a material property that quantifies the elasticity? I thought that yield strength would quantify the elasticity, because a higher yield strength means it can bend more before yielding. Thank you again for the guidance.

 

[rlitman]

You just spelled it out, it is yield strength. However, you said "tensile strength" above, which is not a property we're concerned with in a spring.

 

[MBfreak]

Try to get hold of some old auxilliary relays of a a larger size.
Lots of now 100 % obsolete railroad signalling and telephone exchange circuits used them.
Find the appropriate size and file away to fit.
Will last forever,

Ola

 

[engineer2]

Can you tell us what the part is for or what it's from? With the vast knowledge base at GJ, someone might be able to come up with a replacement. I've seen similar contacts on industrial timers.

 

[The Cobbler]

just tossing out a suggestion, could you rig up a micro switch to replace that switch?