Fixing a Stuck Switch on a Vintage Circular Saw

The switch on my powerful 1970s 71/4 inch Super Sawcat on the left was sticking and then froze in the on position! Not exactly a safe way to operation a powerful cutting tool. No replacements are available anymore so I found a similar saw, a Builders Sawcat to use for parts ( on the right) but its in too good a shape to cannibalize. Plan B was to take the switch apart and attempt to repair it. I found a quick non destructive fix that worked instead.

Screwdrivers to disassemble the saw handle with ( like many old tools it had been repaired previously and required Flathead, Robertson & Phillips screwdrivers) . Electric heat gun. Safety gloves

When I tried my original saw there is no click & it just runs and won't shut off unless I pull the plug.

When I tried the Saw I got for parts the switch makes a very healthy click. and works turning the saw on when pressure put on the switch and cutting the power when pressure is released. Having a comparison to know how it is supposed to sound helps. Even when it worked I don't remember it clicking like that.

When I first disassembled the handle the switch was easy to access and there even was a circuit diagram! I looked online for replacement parts but nothing of that vintage is available anymore and this particular switch has 6 attachment points for wires and any possible modern replacements I might try only have 2 or 4 wires. A second saw I found for parts turned out to be too good to use for that purpose.

Original plan was to drill out the rivets and take the switch apart, lubricate it and hopefully get it back together in working order. Before I started drilling into it I thought about what non destructive options might work. The switch has a brown bakelite like body and opaque plastic on the bottom but no holes or places i could try spraying in contact cleaner. Then I thought to try heating it with an electric heat gun on low setting. That worked!

I heated the switch on low heat, rotating the switch and heat gun so I didn't melt anything. After a few minutes I started working the switch.

For safety I recommend wearing work gloves to protect your hands from the heat. Heatguns can cause burns.

It took a few minutes but eventually the switch started clicking consistently & it has stayed functional even after it cooled down.

Sometimes simple solutions actually work. I plan on trying the same technique on a other old tools I have with with sticky or slow working switches.