I like your idea, You might consider making the screw a tad bit larger than
the id of the existing spring so it will be nice and snug.



If it doesn't work you could always roll your own spring. Just get music
wire the right diameter and make yourself a mandrel for the lathe. With
back gears go slow and make a test run. The loops can be formed by hand.

The spring will tend to get bigger once the tension is off so the ID will be
a bit smaller when winding than when it relaxes.

Alternatively if it is only the hook that is broken you can sometimes make a
new hook from an existing loop and go with that. If the pull is a bit too
stiff, you can stretch it out a little.

Also if you can find a longer expansion spring you can shorten it.

Good luck and be sure to report back on your results.


--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.
"Bob Engelhardt" wrote in message
...
The same neighbor with the broken recip saw has a broken 7" angle
grinder that he'd like me to fix for him.

It's the switch on the grinder that's broken - the return spring on the
trigger has a broken end (it's an extension spring with hook ends).
I've checked the usual sources & can't find this one, but I have a good
repair, I think.

The repair is to make a plug with threads to match the coiled spring
profile. The plug would just thread into the broken end & have the
needed hook. The spring has a very high spring rate & extends very
little, so there would be little chance of the plug escaping during
extension.

As far as turning the threads on the plug, how closely do I have to
match the profile? Can I just use a standard 60 degree thread (with the
same pitch, of course), or do I have to use a form tool to get a
semicircular thread?

This will a small plug: the ID will be 3/32 & the pitch 24 tpi.

Anybody ever done this?

Thanks,
Bob

BTW - the spring is 3/16 OD, 1-9/16 OAL, .044 wire, preloaded - if
someone has a REALLY good source for springs (i.e., much better than
McM-C)