I can't think of an occasion where "to" would be used after "fit".

Other than the phrase, "fits to a tee", not generally. In both of your examples, I would omit the to.

I have heard plumbers and other craftsmen say something like, "Let's fit that pipe to this pipe."

Outside that sort of context, I don't think fit goes with to.

I can't think of an occasion where "to" would be used after "fit".
Isn't that because like "together" in "mix together", "to" is redundant?
And shouldn't it be "Let's fit that pipe onto this pipe."?
Most plumbers are not good grammarians, probably. :-)

And shouldn't it be "Let's fit that pipe onto this pipe."?
Most plumbers are not good grammarians, probably. :-)

Hi, mikefm.

I can't vouch for the grammatical stylings of plumbers, but it's a usage I've noticed several times from plumbers and carpenters, etc. (though, of course, carpenters are then fitting pieces of wood, etc., rather than pipes).

Not being a plumber, I can't say for sure, but I think fitting a pipe onto another pipe is not quite the same concept as fitting a pipe to another pipe. But I could very easily be wrong.

Finally, I note that while the OP seems to ask about putting "fit" and "to" in immediate proximity, my example in #3--"Let's fit that pipe to this pipe"--separates them a bit.

But this formulation can also occur: "This pipe needs to be fit to that pipe." Maybe that example more directly applies to the OP question?

Fit is synonymous with "match"; "it fits him" (no to); and (roughly) with "affix" I'd say. And for affix one can/should say "fit onto". How I see it.

Yes, in my #1 I should have added ...in the sense of "to match", as in the OP's context.