Thanks, all! I'm only doing one fork at the moment, maybe a second one someday. The steerer is steel, so I'll stay with 32 tpi to maintain smooth saw action. I'll use a hose clamp or two to guide the saw. That all should help a lot! I think I'll measure three times, add 5 mm, then cut once, and fix it if wrong. For a steel steerer it looks like my hacksaw blade does not need to be any special alloy.