I only today rediscovered the existence of a splined freewheel interface subtly different to the splined cassette lockring interface. I thought my toolkit was pretty well stocked too.
It turns out neither of my cassette lockring tools fit it; I have two of those because one already didn't fit the almost identical Shimano disk lockring spline interface when it came along.
Even Sheldon Brown doesn't quite make it clear that Shimano cassettes and the freewheels are slightly different.
Aren't old bikes just a joy!?
I thought that was common knowledge? Or at least it was if you ever dealt with freewheels.
It's like the umpteen different cone spanners you need or c ring spanners or bloody Raleigh spec stuff (don't get me started on French standards).
FWIW I own none of those tools and I know fine I need them to sort a couple of bikes I have. I do have an adjustable c ring spanner though so that's one job I might get away with.
A freewheel tool is like a badly fitting cassette tool.
I recently restored a 1980's Peugeot to participate in the Spanish edition of L'Eroica which is held in a hilly part of La Rioja. I needed to find a lower bottom gear from the knee destroying 40/24 that was the norm way back when men were men. Getting the 5 speed freehub off required a tool that I couldn't find for less than £30 and even then was a stab in the dark. The whole bike had only cost me £50. I scoured my parts bin and ended up changing the chainset instead for a 32/44
Having received my new freewheel tool I immediately found the one I already had lurking forgotten in my toolbox. We've since taken our new-to-us 33 year old tandem out for a tentative first ten minutes of awkward starts and stops and picking up speed surprisingly easily.