I had a problem once building up a large frame bike. Could not find a suitable 1" threaded fork with a long enough steering tube. I was able to find NOS 1" unthreaded with hugely long steerers. (I think there was a brief transition stage from threaded to unthreaded that used 1".) So all I had to do was get it threaded. I was advised that it is difficult to start the threads out square, so I should ask lots of questions before paying someone to do it.

I did ask lots of questions. A couple of bike places said they could do it, but did not inspire much confidence. One place though seemed to have done it before and seemed to know what they were doing. I paid them a small amount (maybe $15?) to do it. Worked great. Still use that bike today and have not had one problem.

A previous poster mentioned that unthreaded forks might not all have the same (usable) inside diameter. I cannot speak to this except to say it was not an issue on the fork I used.

jim