I have had to replace the switch on my Sears Craftsman radial arm saw several times. I use a pushbutton single pole, single throw (SPST) switch from Radio Shack. It is stock number 275-671. The retail price is $ 5.99 US plus sales tax.
(The red rectangle is a label with my name. To be cautious about Internet security I made it illegible for this photo.)
Step 1: My radial arm saw
This Instructable applies to Sears radial arm saws that look like this one (The photo is from an earlier Instructable.) This series of saws was made from the late 1940's through the early 1970's. My saw was made in 1972.
Step 2: The original switch
I no longer have an original switch, but used a photo editing program to create the image of an original switch in place. It had a red button to stop the saw and a green button to start the saw. The yellow arrow points to a keyhole for a stamped metal key used to lock the switch so the saw cannot be turned "on" accidentally. Metal tabs flank the green button to avoid accidentally bumping it and turning the saw "on" when not intended.
The main reason I no longer use the original style switch is that it was no longer available through Sears parts depots just a few years after I purchased my saw. In addition, these switches lasted about six years for me and (at the time) they cost more than twice as much as the Radio Shack pushbutton switch I used to replace the original design. I am now on my 2nd switch from Radio Shack. The first one lasted 26 years for me!