2 lead threading in a manual lathe

[cherokeechief79]

we are tryin to cut one of these in class tonite and I was going to cut one to depth and then advance the toolpost one thread pitch to cut the other.one of the students read in an old book that you could just hit different cobinations of lines and numbers on the threading dial.anyone ever do this?

our threading dial has 4 numbers and a line between each.

[crazy^millman]

4 Jaw chuck and mark your 0 and 180 degree jaws to know where to start for those leads and should be good to go. Can be done with 3 Jaws, but mark your 0 and 180 positions. Also mark Your thread chase dial to know which one is your 1st lead and which one if your 2nd lead.

[cherokeechief79]

thanks but your saying it can be done without releasing the part from the chuck?

lets say im going to cut a 1 inch 20 double lead thread.ill set it up to cut 10 threads per inch but what should I be hitting on the thread dial to alternate between the two?

[Matthew Hajicek - Singularity]

Which numbers you can hit on the dial depends on the pitch of the thread.  For some you can do any of the four, for some you can do opposite numbers, for some you have to always do the same number.  So for dual lead and a thread that requires you use the same number, you could alternate between the one and the opposite (1 and 3).  For one that normally you could use opposites, you can alternate between (1 or 3) and (2 or 4).

[buck30]

put the compound slide to Zero degrees, cut one thread then move  the compound slide the pitch between the 2 starts then machine the second start. As Metthew said above chances are the opposite thing on the dial most times won't work.

[cherokeechief79]

ok we will try this tonite.

I know already we can cut a even thread pitch by hitting any number or line and it will track down the same path.

[Matthew Hajicek - Singularity]

ok we will try this tonite.

I know already we can cut a even thread pitch by hitting any number or line and it will track down the same path.

 

Then you have to use Buck30's method.

[#Rekd™]

+1 to Buck.

 

If it is a 2 start thread you are esentially cutting 2 individual threads.

 

I have cut internal double start threads in a blind hole as small as #10 size on a manual lathe.

[jlw™]

Don't try to go back and forth no matter what method you use.  Take one lead to depth then the next.

[cherokeechief79]

we wound up cutting one and then advancing the compound to cut the other.

it worked great.

the class left happy!

next week we cut the internal.

 

the question came up about cutting a 3 lead thread in the manual and I said I would have to think about it.

it might be a little hard to divide up the threads available on the manual into 3 .