thread cutting

[irishwoodsman]

New journey beginning, Its my understanding when cutting a thread useing the threading dial you engage your machine when the dial lines up with the number on dial, does this mean i can engage maybe a 1/2 before my tool gets to the material, the reason i ask this some times i have to hold my hand wheel and tighten the clutch cause if i just tighten the clutch my hand wheel wants to move with it, i think there is some play behind the carriage some where:thinking:

 

[GK1918]

I have read your question five times and still confused. The clutch? or atleast thats what I read. Best of my
knowledge I never heard of using the clutch for threading unless you have some kind of different or special machine.
The half nut has been the standard since Ive been around. As far as the thread dial, that depends on the thread you
are about to cut being lines or numbers. There is much written on this and everyone has their style. Myself as far as
the dial goes (most dials can be swung out when not in use) I set the machine for the desired thread, then I engauge
my half nut for a little bit (to get rid of backlash) which they all have, then shut the machine off, then engauge the
thread dial so it lines up (mesh) with a line or number. Now it is in sync. Disengauge half nut start machine and now
engauging half nut it should pop in matching on lines or numbers, then the dial stops rotating (until) the half nut is
disengauged for the next pass. If the dial is revolving while the carriage is moving there is something wrong. Although
it could be possible to thread with the clutch by messing around with change gears (maybe) My oldest lathe was
made in 1918 and that has a half nut, my newest is a 1942. I think it would be good to tell us about your lathe. sam

 

[irishwoodsman]

maybe i explained it wrong, i've got a 1946 sheldon 11" lathe on the apron it has a dial which is the clutch dial, oops i know now the clutch is used for regular machining, and the leadscrew is for the thread cutting when engaged with the gear box

 

[irishwoodsman]

the question is though, when useing the thread dial at the end of each pass as long as i engage the feed when the thread dial comes to the top of the number the cutter will pick the thread back up in the same place

 

[irishwoodsman]

You should NOT be fiddling with the clutch at all when threading. This is done 100% with the engagement of the half-nut. When you engage it (and yes, 1 or more threads away from the start of the thread is good), the threading dial stops rotating because it's gear is now traveleing in perfect synchronization with the carriage and lead screw.

GK1918: What is the reason people swing the threading dial out of engagement when not in use? It really doesn't move much as you run the carriage back and forth, so what's the big deal?

understand, went brain dead for a secound:thinking:

 

[irishwoodsman]

this is a first for me on cutting a thread and i do have a lever on my carrage that engages the leadscrew with a built in safety so you cant engage it unless your compound is disengaged, which is great, when i come to the end of my threads is it better to turn my lathe off and bring the carrage back to the starting point or can i stop put my lathe in reverse and bring carrage back and then start my forward travel again:biggrin:

 

[GK1918]

Ya Paddy I know its just an old habit turning off lights, beer, forgetting to write notes, habits. No really I bought this
thread dial for $20 its from an Atlas but works but its well worn thats why I do that. Most if not all my threading is
for the big stuff that you cant buy local, boat shafts, fair amount of left hand treads (farm stuff).. One big help as
far as threading I bought for my lathes is those big soft rubber floor mats and people of this trade look at me funny
cause my most used SB I raised it way up so I dont have to bend over. Like said whatever floats Ya boat.

 

[Tony Wells]

this is a first for me on cutting a thread and i do have a lever on my carrage that engages the leadscrew with a built in safety so you cant engage it unless your compound is disengaged, which is great, when i come to the end of my threads is it better to turn my lathe off and bring the carrage back to the starting point or can i stop put my lathe in reverse and bring carrage back and then start my forward travel again:biggrin:

When cutting metric threads on many lathes, this is the only way to ensure that the lead screw and spindle stay in synch. But you MUST withdraw your threading tool before you reverse the spindle, as the backlash will allow the spindle to turn a bit before the tool starts moving, which will without fail break the tool or cause some other undesirable consequence. Normally, people in general disengage the half nut at the end of the thread while simultaneously pulling the tool out of the cut. Kind of depends on whether you have a thread relief groove of not. Just make sure you know about your lathe and whether you can re-engage the half nut on any line, or only certain ones. Different threads require different approaches.

 

[irishwoodsman]

Thank you tony thats what i needed to know. i watched a few vids on this but it was all done with newer lathes, i didnt know the dial would stop once the lead screw was engaged i guess i thought it worked like a travel dial, you learn something new every day i guess, but thats the fun of it. here's another question, does it matter what diameter you use as stock, what i mean is could you put a 2-1/4 8 tpi on a 1inch peice of round bar, i know the 2-1/4 is the diameter but will the threads be spaced the same, this is just practice

 

[irishwoodsman]

wow that explained alot right there, i got some aluminum round bar going to practice with before i try my hand at the hard metals, kinda started this to see if i got a odd ball gear on my lathe, fig i would cut a standard thread and if the nut fits it then i know the gear belongs on my lathe:thinking: thank you so much for your help:biggrin: