do it backwards
dee
;-D
Bit TEDIOUS to have to go and use another computer to view that. Yeah - he eventually got to the point, and even got me thinking a QCTP vs my beloved 4-ways might not be a BAD idea after all, wot with that "lift" fail-safe.
OTOH.. here's what also works - especially if.. the part is massive, costly, rare, etc - and the lathe is OLD, no stops, no QCTP, not a lot of "goodness" left in its bones of any kind.
Power-off..
- manually place the tool-tip where you plan to start walking AWAY from a shoulder or other feature.
- Engage threading.
- Engage half-nuts.
- Dig the HSS-not-Carbide tip INTO the metal. (F**king carbide would chip..)
- Tommy bar it to insure all is going the needed direction and in sync.
- NOW engage power & clutch whilst advancing tool the rest of the way for that pass.
Go light up a Camel. Or so was my won't back in the day.
Worst case, the threading tool is 6 feet down-bed clear of the 6" long thread on the work. No foul. Still four to six feet clear.
Now. REPEAT that finicky power-off and tommy-bar initial manual tool sync and alignment
each go. It is the ONLY critical step, after all. All else is vanilla threading 101 - just upside down tool.
Even on a nineteen-teens clapped out Niles fifty-incher, yah gets a downright lovely looking start to a good thread. That simple. That common back in the day. The video-maker's Grand Dad wudda been laffin' at how he made a "big deal" out of it.
The Hendey dog-clutch assist works really well. So, too the Cazeneuve system.
The Monarch 10EE earliest-days manual LSR and later Electrical LSR do NOT, in fact, work quite as well as either of those other worthies. More "latency" in the ELSR reaction time is unavoidable.
By cutting AWAY from a shoulder or feature, it simply no longer matters. Great lathe, average lathe, or outright POS lathe - we are not ASKING anything critical of it.
KISS method.