Playing around with a spare switch plate during the vacation. I spoke to Ben Martin a few weeks back and he walked me through some of the steps he uses for restoring function on warped switch plates.
I started by cleaning the plate with Eagle One Chrome Wheel Cleaner and a fine tooth brush. Then washed it in water with a little baking soda to neutralize the acid from the cleaner. I let it soak in warm water for about twenty minutes and after drying it off with a paper towel placed it between two large washers.
I drilled relief holes and made a cut out in one washer so the pressure would only be on the fiber disc and not the brass contacts. I also placed thicker washers (drive shaft thrust bearing races) on either side of the thinner washers. Then I placed the steel sandwiched disc in my vice and pressed the stack as tightly as I could using a pipe on the vice handle.
I left the disc in the vice for 24 hours and when I pulled it out it was perfectly flat. Then I carefully brushed a thin coat of sanding sealer on the edges and the sides of the disc and allowed them to dry. When dry a slight warp reappeared, but it was still much better than before. I think it might be better to seal the edges before removing the pressure. Iíll let it dry for another day and then sand the back of the disc using sand paper supported on a sheet of glass. Then Iíll give it a final coat of polyurethane and clean the contacts.
Two more pictures. The other side of the switch plate with the two washers placed against it. One is a thrust bearing race. The other shows the disc being pressed in a vice between the steel washers.
I also had to replace one of the threaded inserts. The one to the right is a new insert that was screwed and glued into place. After inserting I beveled the open with a large drill bit turned by hand to shave off just a little.
Very nice work. Thanks for taking photos of it.
I haven't worked on a lot of switches. How common are punched-in stops like those? All I've seen so far were round hemispherical depressions.
The depressions are on the side where the sliders run ... the raised brass fittings are the side where the wires are screwed down.
I like the cutout and drilled washer idea AND the fact that some lettering transferred to the washer!
I echo Steve's comment. Worked on a B&S Co pin type lately and the depressions are spherical also. I see yours is a B&S Corp switch.
If Larry sees this thread he'll tell about super glue for these switch plates. :-) He's correct. :-)
Thank you for posting this.
I did use super glue for inserting the replacement threaded insert. Canít imaging Larry using super glue ... it would have to be something like Spar Varnish to be an authentic and approved vintage repair. :-)
I assume you are referring to painting the disc with cyanoacrylate as an overall coating. Well, I havenít done the final coat yet .. so I could do that. I wonder if it would be better than polyurethane.
An update: I pressed the disc again after the sanding sealer dried and the disc reformed back to the very flat surface it was when I first removed it from the vice.
No I think you fill the cracks around the edge with supper glue then press the half's back together. The card/paper substrate become de-laminated. This may not be as much an issue with the tab type but as the paper substrate comes apart the pins pull out allowing the disk to ride up in that type.
Oh .. I see. Must be more of a problem with the pin type. The fiber disc on this one was the tab type and not delaminated. It was warped.
All I use is the pin type switch backs. I use no water either. As I've said many times on this forum I take a switch back and sand it on a surface plate, or drill press table until it's relatively flat. I only use the Crazy Glue on the warped areas. Since there are three pins, I clamp those while the Crazy Glue is still wet in a vise back to the original thickness. This method has always worked for me. I have an original pin type switch back on my '25 which I restored with Ben's approval years ago, and it works fine. I don't think anyone could tell it from NOS!
I did this tab type switch back based on Benís instructions. Since people seem to respect his restorations ... I thought it was a good place to start. If it had been a pin type it makes good sense to introduce the Crazy Glue into cavities then clamp it tight until set. For the life of me I donít know where you located the original 1920s Ford Crazy Glue. ;-)
But the reason for warping is probably due to relative humidity ... or lack of it on the aged material. So, wetting the compressed fiber and then pressing it back to spec seems to work fine. Then the trick is to apply a finish after pressing so that it canít absorb or release moisture again. When it was new there was still the original binder in the fibers to prevent it from absorbing moisture.