How to uncrimp this without damaging it? (Repairing antique switch)

I'm planning to disassemble an old switch to repair it but the panel with the contacts is crimped in place. Does anyone have any ideas of how to remove it without destroying it?

I've uncrimped a number of similar type devices with variable success. Hard to tell precisely from your photo, but I would approach it with a pair of pliers modified so one jaw is longer (to lever against the metal below the crimp) and the other jaw ground with a chisel point to get behind the lip of the crimp. That case almost looks like corroded aluminum so bets are off that the crimp will bend without cracking.

I've done ignition switches like this. One cheat is to simply machne away the crimped-over area to
diassemble. Often if you manage to uncrimp it, things do not go well when you try to re-crimp, the
crimped area then cracks off.

If you machine it away you don't damage the underlaid insulator, and then the choice is on now to
re-assemble, an adhesive will work sometimes.

jim rozen said:

I've done ignition switches like this. One cheat is to simply machne away the crimped-over area to
diassemble. Often if you manage to uncrimp it, things do not go well when you try to re-crimp, the
crimped area then cracks off.

If you machine it away you don't damage the underlaid insulator, and then the choice is on now to
re-assemble, an adhesive will work sometimes.

Click to expand...

100% agree on machining away the crimp.

Choices for reassembly:

Silver epoxy
Low temperature solder
Drill and tap terminal
Replace terminal completely with copper or brass rivet (best for appearance and electrical integrity)
Use brass screw and nut to replace terminal

PS: Copper nails can be used as replacement rivets if you can find some in the correct size.

I often replace rivets with nuts and bolts. You may have room in there to use nuts and bolts for reassembly if the crimp can not be redone.
Bil lD.

I'm not sure what repairs need to be done to those contacts, but can you do them without removing them?

I think the first thing I would do with that is treat it to an hour or so in the ultrasonic cleaner. Perhaps first with a soap solution and then with vinegar.

You can't just pry it out with a screwdriver? I've done this many times to fix old relays. Never had a problem. Most metal cases are ductile since they're formed in the first place.

Would be my first suggestion...

As long as the plastic insulator (that the metal part is crimped around) is strong enough to handle the
stress, that will work. If it isn't then the insulator crushes and that's often the hard part to replicate/replace.

Dismantling stuff like this is seldom a one-size-fits-all situation.

Bill D said:

I often replace rivets with nuts and bolts. You may have room in there to use nuts and bolts for reassembly if the crimp can not be redone.
Bil lD.

Click to expand...

And if someone has a metal lathe (anyone we know ) they can easily make a few brass rivets or screw posts. In the case of a DIY brass or copper tubalar rivet heating the end to red hot and quenching in water will make it soft and easy to crimp.

I even once made a replacement for a missing brass screw-on collar for a favorite pair of electrical meter probes and nickel plated it using a brush plating solution.

I had to re-insulate some ancient industrial lighting. The old insulation between the "fitter" (part which clamped the steel reflector and connected it to the socket base) was crumbling. Part of the fitter screwed right onto the outside of the metal socket for the bulb, and was enclosed in a porcelain socket base. The result was that if I had used the lighting as it was, the fitters & steel reflectors would have been "hot" (electrically energized). Parts were assembled with very small metal rivets, with a layer of some sort of insulation (which had crumbled with age) between them, and sufficient clearance around the rivets to avoid forming a current path.

I drilled out the rivets, and re-insulated using a new flexible material (some EPDM or neoprene sheet, IIRC). I replaced the rivets with black delrin screws and nuts, which solved the insulation problem handily. I got these materials from McMaster Carr. Wife is delighted with the old industrial lighting in our kitchen.

I've dealt with crimped electrical parts on old motorcycles. Typically, I get lucky and with a sharpened small screw driver and needlenose pliers, have been able to pry the crimping away to open up parts to access contacts, etc. Putting them back together, I've also been lucky as a rule.

For the contacts in the picture posted by the OP, I believe I understand what needs uncrimping. It looks like the contact prongs are riveted to a molded piece of insulating material. The crimp comes in from the sides to hold that molded insulating material. Given the amount of corrosion and apparent age of the part, as well as the type of crimping, I would not be too optimistic about uncrimping/recrimping. Here are two ideas, but not knowing the whole anatomy of the assembly the contacts are on, I can't say with certainty they would work (space constraints within the device being one concern).

-uncrimp the existing block of insulating material with the contacts on it. Do whatever repairs you need to do to the contacts and wiring connected to them.

-Examine the aluminum (or die cast alloy) housing the contact assembly is crimped onto. If the contact assembly is seated on a "pad" with a hole for the wiring, there may be enough room to re-secure the contact assembly using some nylon or delrin screws. Small screws, either counterbored or countersunk so they are flush with the insulating material's surface and tapped into the lip or pad on the housing that the insulating material seats on would be one idea. Bed the insulating material on some epoxy adehsive aside from the small screws.

-If the housing does not have a pad or lip with enough material for screws to anchor the contact assembly, another idea is to make a new insulating block, making it thicker than original, if space in the housing permits. This insulating block is then secured into the housing with small screws coming in from the sides. The old rivets on the contacts are drilled out, and a variety of methods can be used to re-secure them. Using brass screws and silbrazing them to the contacts, with enough length to go thru the new insulating block. A nut then secures the contacts to the insulating block, and wiring can then be re-connected to the projecting length of the brass screws. Using silbrazing, the threaded shanks of the screws are brazed solidly to the contacts, and heads of the screws can be filed down as needed to approximate the original rivets. I've used "Micarta" or "reinforced phenolic" for this sort of replacement of parts similar to what the OP shows. Micarta or reinforced phenolic (aka "Bakelite") is readily machineable, can be drilled and tapped, and is quite strong as well as having good electrical insulating properties.

A thicker insulating block to mount the contacts on, with possibly a step machined in its edge so it "nests" down into the housing would be an idea to explore. By making the insulating block thicker than original, screws run in from the sides will really secure the contact assembly. Trick is not to tap so deep or in a location where the screws contact the brass screws holding the contacts to the insulating block.

Joe Michaels said:

I've dealt with crimped electrical parts on old motorcycles. Typically, I get lucky and with a sharpened small screw driver and needlenose pliers, have been able to pry the crimping away to open up parts to access contacts, etc. Putting them back together, I've also been lucky as a rule.

Click to expand...

You should be aware that the ignition switch on your BMW is an NLA part. You can't get those anymore, at best a repro. In my case the switch failed in the worst
way: intermittent. The ignition on my R75 would quit at random times, while riding. VERY dangerous. Cycling the switch would bring it back every time. I went
though a long list of possible intermittent fails before I realized what was going on - and simply replaced the key switch in the headlight with a bar mounted toggle switch,
which cured the problem once and for all.

Easy, says I. I'll just uncrimp it, clean up the contacts, and re-assemble. Contacts were pretty worn and installed in the insulator so it was tough to renew them. Then
crimping the shell back together, did not work out well in spite of the fixture I made. The bike still sports a heavy duty toggle switch on the handebars. Putting a
repro in would mean having two keys for the bike (ignition and fork lock) which is too complicated. Plus the repros look to be made pretty cheesy.

jim rozen said:

As long as the plastic insulator (that the metal part is crimped around) is strong enough to handle the
stress, that will work. If it isn't then the insulator crushes and that's often the hard part to replicate/replace.

Dismantling stuff like this is seldom a one-size-fits-all situation.

Click to expand...

All true.

Just my opinion, but if the insulator can't stand some gentle prying action, it needs replacement, too.

Being cheap we have done this many times.

Metal is usually soft so no worries.

Place in vice with edge of vice jaw at edge of metal.

Tiny chisel or modify small screwdriver to fit.

Light tap with sharp edge and it separated.

Regular blade now to finish.

A knife may be needed to open it up, reposition in vice to now allow side to bend a bit and place in a plastic bag first so all parts are captured

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Tony Quiring said:

....place in a plastic bag first so all parts are captured

Click to expand...

Often contain tiny springs or other parts that are expelled at the speed of sound! Bag or box *definitely*
required. Also safety glasses....