That is interesting. It makes sense. I cannot even imagine getting all that set up in a vice nor can I imagine a vise of that perfection outside a machine shop.

In distant past mechanics I knew did this entirely freehand. Or with just a vice grip, or a basic bench vise, or just a file sitting on a bench top. Should have been paying more attention. Perhaps this is simply a very difficult job and there is good reason it has always been taken to a mechanic. Except there is no longer a mechanic.

Two very senior mechanics I have been talking to tell me that in any LBS once the Var tool first arrived no one ever filed a cotter again. Only exception being the most troublesome cases, then it got passed to the old guy. Who filed.