But a good Machinist can roll threads , they have to be tooled up for it.

My father was a retired machinist when he passed .. made Armaments for the US Navy.

True , the usual fork threading die is a cutting tool.


to the OP : dont bother with the threading, just do the threadless conversion. thereby leaving steel tube wall thickness unchanged.

[otoh]
I used a long threaded steerer tube on my Touring bIke.
a mid ride frame repair had me knock out the headset,
got the welding done , then, I

found the long thread offered a built in headset press when
time came to put it back together ..

with just the short 32/15mm wrench I had for removing the pedals.