Thread dial question

chips&more said:
I’m not sure about the amount of carriage travel with one revolution of the threading dial? But, it definitely sounds like something moved on you. If you always start/engage on the same thread dial number, it will always cut on the same thread cut. Or maybe you did not engage the half nuts all the way, that will give you the problem you are having...Good Luck.
Click to expand...

I am sure I didn't miss the settings and it is possible I did something wrong but I don't think so however the thread dial should have worked on any number or any line on this setting so somewhere something I did must have changed it. I just do not see what I did incorrectly.

maybe I need to look at the half nut to see if it is worn or something ... I don't know what went wrong as I thought I had it all set up and ran it right. ( beginners learning curve !! )

- - - Updated - - -

Tozguy said:
Wouldn't it be a bit$h if the thread dial screws were loose and it was skipping on the leadscrew.
Click to expand...

nope that was the first thing I looked at...
 
john mullen said:
I am sure I didn't miss the settings and it is possible I did something wrong but I don't think so however the thread dial should have worked on any number or any line on this setting so somewhere something I did must have changed it. I just do not see what I did incorrectly.

maybe I need to look at the half nut to see if it is worn or something ... I don't know what went wrong as I thought I had it all set up and ran it right. ( beginners learning curve !! )

- - - Updated - - -



nope that was the first thing I looked at...
Click to expand...


Take a look at the gears between the spindle and the gear box. I suspect it might be set for metric threads. You may need to swap 2 gears around.
 
Don B said:
B 1 looks right is there a gear train form the spindle to the QC gear box that could have an improper gear installed in the wrong position..?
Put it in B 1 and engage the split nut, put an indicator on the saddle, rotate a little to remove backlash, then rotate the spindle one turn an see what you get (all by hand)[/QUOTE

after the first pass I stopped the lathe and backed the cross feed out one full turn and moved the saddle back to the start. I then checked the threads with a pitch gauge and all was correct .I then ran the cross feed back to the 0 as where it was on the first pass . I then moved the compound in .010 and dropped the half nut in on the same number and it cut a new thread about half way in between the threads on the first pass. It should have been correct ???
Click to expand...
 
john mullen said:
Don B said:
B 1 looks right is there a gear train form the spindle to the QC gear box that could have an improper gear installed in the wrong position..?
Put it in B 1 and engage the split nut, put an indicator on the saddle, rotate a little to remove backlash, then rotate the spindle one turn an see what you get (all by hand)[/QUOTE

after the first pass I stopped the lathe and backed the cross feed out one full turn and moved the saddle back to the start. I then checked the threads with a pitch gauge and all was correct .I then ran the cross feed back to the 0 as where it was on the first pass . I then moved the compound in .010 and dropped the half nut in on the same number and it cut a new thread about half way in between the threads on the first pass. It should have been correct ???
Click to expand...

Yes exactly it should have, but I'm describing a method to determine if B1 is giving you .125 per revolution of the spindle just to see where things stand and to see where to go from here.

Edit: have a look at Jim's post above, I think he called it right.
Click to expand...
 
Don B said:
B 1 looks right is there a gear train form the spindle to the QC gear box that could have an improper gear installed in the wrong position..?
Put it in B 1 and engage the split nut, put an indicator on the saddle, rotate a little to remove backlash, then rotate the spindle one turn an see what you get (all by hand)
Click to expand...

I'll do this on Saturday and see how much the saddle travels. thanks for the input ../John
 
A clear photo of the gears at the outboard end of the headstock would help other Jet owners to help figure it out.
 
If the pitch which was checked with a gauge was correct, I don't believe it is a gearing issue.

My first question is what degree is the compound set to?

Is there end play in the lead screw?

How much wear is in the half nuts?

Is the lead screw shear pin or friction clutch protected?
 
My lathe is not a Jet, so I don't know how similar they may or may not be. I was also making a 1 1/2" x 8 thread for the first time on a different machine. I made my first pass, and noticed immediately that something was not right. It made a 1 1/2" x 4 instead of 1 1/2" x 8. I looked at the side gears, and the stud gear was a 48T instead of a 24T. Put the 24T stud gear in and then all was right.

Very strange that your thread pitch was different between passes even though your settings had not changed. Is your threading dial fully engaged with the lead screw and tight enough to stay put?

Hope you find your gremlin.

GG
 
First have you cut threads on this lathe before and did thay come out fine? And did you shift the lathe into nutral between cuts by chance?
 
You must log in or register to reply here.
Back
Top