The same items, with the return spring
disassembled, showing its components.
The spring is ten turns of .065" piano wire,
wound on a 5/16" mandrel and then stress
relieved for an hour at 500 degrees F. It's
The bolt is about 1-3/4" long, threaded
1/4-20. Its head is 7/16" square, allowing
it to be turned with the same wrench as is
used on the tool post. This also allows the
bolt to be turned from 1/2" stock.
The small top collar turns out to be
unnecessary, since there's a collar turned
right into the bolt head. Still, if the
spring had turned out to be a little wider,
it would need that top collar to retain it.
The bottom collar is wider than the top one,
to make sure it catches the edge of the
clapper (or in this case, the nonskid tool
pad). It has a flat turned on it to clear
the clapper without having to remove the
whole spring assembly.
Top and bottom collars are a sliding fit on
the bolt. I suppose they could also have
been made a close fit on the inside of the
spring, too, but I made them before making
the spring. It's tough to predict what the
final diameter of a spring is going to be.