The Natural Philosopher wrote:

On 13/03/2019 09:54, Roger Hayter wrote:
I'd still try a new microswitch first. Their operating point does move
a lot as the contacts wear.

No. it doesn't.

If you look at how they work, it is a matter of levers within the thing
whose actions are more about where the button sits on the arm and the
arm length than where the contact is

https://www.components.omron.com/web...tch/basic02-01

what wears, is not the contact, but the actual BUTTON.

If the actuator has a mechanical advantage (which it does to a degree
dependent on the type of actuator) then wear at the contact will be
magnified by that advantage. I recently replaced a microswitch (with
one I had in stock since the early 1960s!) in the pressure switch in a
Saniflow macerator and found the nylon button had to be depressed to
nearly level with the case, while a new one moved about two mm. The
button wasn't visibly worn. So, n of 1, I disagree. You may be right
in other cases, my experience is limited. But contact wear or possibly
bending little metal parts was certainly the cause in my case, not
actuator wear.
--

Roger Hayter