Bill Tindall, E.Tn.
I didn't ask if I needed a cap iron. If you go to the Gallery section you will find that I build stuff, a lot of stuff, only a fraction of which I have posted so far. It doesn't fall on a receptive ear being told what I need to build the stuff I build, the way I build it. Well, it might fall on a receptive ear if the advice givers offered some evidence that they too built a lot of stuff and didn't have but an inexpensive plane or two to employ in the building of the stuff they build. Sorry, but a video of flattening a piece of oak didn't do much for someone that would have done it on a jointer in a few seconds and gotten on to flattening the dozens of other pieces of wood necessary to make something.

I find a cap iron useful. Period, end of story. I have no interest in a discussion otherwise, though others are encouraged to argue its merits, in your own posts, and not hijack mine trying to ask a question. I would be delighted if the irrelevant posts to my question were deleted and resumed in a separate discussion of cap iron merit.

I'll get it stated by asking why the hell they were invented if they weren't useful to the people earning a living making furniture using them. Maybe one has to build stuff to discover the answer, I don't know. Answer elsewhere.