After approximately forever, the shackle on the Corbin K436 padlock securing the tandem-length cable we use for the Tour Easy ‘bents refused to push into the body. Lubrication being unavailing, I soaked it in acetone and shook it around for a day to get the inevitable crud out, then pondered the problem.
Peering into the hole where the shackle enters the body showed the situation:

Half a century (more or less: it didn’t accumulate those nicks & dings & tarnish last year) of pushing the shackle into the lock eroded the locking cam, to the extent that the cam no longer slides sideways to let the shackle slide the rest of the way into the body.
So I introduced the shackle to Mr Bench Grinder and reshaped the end to hit the cam farther down on its angled side:

While that certainly reduces the strength of the shackle, there’s a similar notch engaging a similar cam on the other end of the shackle, so it remains as secure as it must be for our simple needs.
Spraying silicone lube into the body and applying a dab of silicone grease to the cam restored the lock to (nearly) new condition.
The riding season approaches!
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