Let's clear some air.

First of all before considering the technical aspects, what is the intent for doing the job? If you're looking to cut the steerer to the final height and do a classic quill stem install, then it may be worth pursuing, and it may be possible. If you plan to leave the unsupported threaded section above the headset for some reason, then it'll be problematic for a number of reasons, whether it's possible or not.

So, assuming, you're attempting a classic build, with the fork length being equal to the headtube length + threaded headset stack height, including up to 5mm of added spacers under the locknut, here's what to consider.

1- the steerer must be steel,
2- the ID must be 7/8" (or 1" on a 1-1/8" fork) to match the existing quill stems, and have the 1/16" wall needed for the job. Many, but not all, steel threadless steerers meet this requirement.
3- the tube must be sufficiently soft for cutting, which can be verified with a file test.
4- you need a proper die and handle, plus a cutting oil made for threading steel.
5- you need some basic skill and knowledge. The job is relatively simple, but has pitfalls, and is easy to botch. It's that ease of botching that has given this job an unearned reputation for being impossible.

Over the years, I've cut and threaded countless hundreds of forks, and so far, enjoy a 100% success rate. But part of the reason is that I qualify the job before starting.