Lead screw or thread dial not right?

jareese

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So I’m practicing on cutting 24tpi.
I have a 4tpi lead screw supposedly.
I start on number 4 on the thread dial. I “should” be able to go on number 2 as well, right?
When I try, it gives me like a quarter thread or so. Not quite half??

Eisen 1440EV
 
So I’m practicing on cutting 24tpi.
I have a 4tpi lead screw supposedly.
I start on number 4 on the thread dial. I “should” be able to go on number 2 as well, right?
When I try, it gives me like a quarter thread or so. Not quite half??

Eisen 1440EV
Depends on your machine but I've never restarted on a different number.
 
So I’m practicing on cutting 24tpi.
I have a 4tpi lead screw supposedly.
I start on number 4 on the thread dial. I “should” be able to go on number 2 as well, right?
When I try, it gives me like a quarter thread or so. Not quite half??

Eisen 1440EV

Is your lead screw really 4 TPI? That would mean it has a thread crest every 1/4”.
Are you sure it’s not 8 or 10 TPI?
 
I forget what the general "rule of thumb" is for the thread dial, if you search online should be able to find it.

But your lathe should have a chart for the thread dial showing what thread pitches can be enaged on what numbers & lines. If the thread dial chart is not on your gear train cover with all the feeds & thread pitches, check on the side of your apron. I've even seen the chart on the side of the thread dial itself but I assume you would have noticed that already.
 
 
My lathe has an 8 TPI leadscrew, so for cutting 8, 16, 24 TPI etc, I should be able to engage the halfnut anywhere, no thread dial needed.
 
My lathe has an 8 TPI leadscrew, so for cutting 8, 16, 24 TPI etc, I should be able to engage the halfnut anywhere, no thread dial needed.
Exactly. Same with 4.
What would cause it to not “line up”?
 
are you sure your lead screw is that coarse?
Don't know what would cause it not to line up... but on my 8tpi SB 9 I can do even # threads on any marking.
 
What would cause it to not “line up”?
No idea, unless you're not actually set for 24 TPI. If it was say 28 TPI I would say check to see if the thread dial gear is loose. It happens & on some lathes that gear is not keyed. But if you're set for 24 TPI should be able to engage anywhere.

What method are you using for advancing DOC? Cross slide or compound slide?
 
The thread dial rules depend on the lead screw pitch, the number of teeth on the thread dial gear, and the numbers on the dial.

My lathe has a 12 tpi lead screw and 36 48 teeth on the gear so the dial makes a complete revolution every 3 4 inches. There are 12 marks on the dial so for any thread evenly divisible by 3 the half nuts can be engaged on any mark. For the remaining whole number pitches, the half nuts can be engage on every third mark, For 1/2 number pitches, the half nuts can be engaged on every 6th mark. Were I cutting a 1/4 number pitch, I would need to engage on the same mark.

Edit: I misremembered my setup> Corrections above.
 
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