I have a 1900-91ish Merlin with the press fit bottom bracket. Which has been fine for 20 plus years of riding. I don't find it a problem to beat out and replace the bearing every couple of seasons.

But I'd like to totally replace the BB with a threaded one. Does anyone have any experience with having that done? From what I can tell, there seems to be only a few bike builders who even want to deal with that. Or am I looking in the wrong places?

What are people's experiences with the bike after having that done?

things to consider: 1) having enough thickness in BB wall to cut threads that will hold a BB. 2) proper size BB shell to hold thread-in type BB. 3) finding someone that has the equipment and know-how to cut an inch or or of threads in both sides of the BB shell.

i won't be surprised if there are those that will get into why this is being attempted. good luck though.

however, there are some press-in adapters that fit a certain diameter of BB shell that may be of help. for instance, BB30 to BSA. maybe PF30 to BSA.

like this:

The BB tube on a Merlin with the press in BB is too small of a diameter to thread. The BB tube will have to be cut off and a new threaded BB welded on.

A few Ti builders apparently will do this. Most, including, interesting enough, the guy who designed the frame, won't touch it.

Id just stick with pressed in bearings, you may consider Velo Orange's threadless BB Grand Cru Threadless Bottom Bracket

but that's still square taper , wont let you get in the latest External Bearing high end cranksets . <I guess that may have been the plan>