Cross Slide Stop for threading on my 13" South Bend?

Hello,
I am struggling to return the cross slide back to the zero point in order to feed the compound in for another pass when threading.
I have a single gear box (1941) 13" South Bend. It has the small dials with some backlash like all lathes.
If I could dial back the cross slide to clear the threads, move the saddle back to the starting point then move in the cross slide to a positive point each and every time, then I could feed the compound with confidence.
I am looking for the locking device, guide, stop or whatever will perform the intended cross slide location.
Thank you for your help and I apologize for my ignorance, I don't have very much experience.
Jeff
 
Establish your cross slide and compound slide zeroes after turning both of them in to just touch off on the piece to be threaded. All of the backlash will have been taken out of both lead screws in that direction. Then when you back the cross slide out before returning the carriage for the next pass, backlash will make that dial no longer an accurate reference for the exact amount you have backed the slide out. But, that is immaterial to the threading process. Just be sure to keep track of the number of turns that you backed it out. When you crank the cross slide back in, the backlash will be taken out and the dial will again be accurate. Crank it in the same number of turns that you cranked it out and align the zero and you’re ready to advance the compound slide for the next pass.

Tom
 
Establish your cross slide and compound slide zeroes after turning both of them in to just touch off on the piece to be threaded. All of the backlash will have been taken out of both lead screws in that direction.

This is what I am struggling with, you say the backlash will be taken out after moving in. What I find is, when the pressure of the tool touches the piece I am threading, the compound moves back slightly. I assumed this is the back side of the backlash. Since I know it is going to come back a bit, I am thinking I should physically pull back on the compound while moving it forward. In this way, I have a more accurate measurement of depth cut.
If this does not make sense, maybe I have something else loose or worn that I am not aware of.
I just had a thought, maybe my brass nut retaining screw is loose causing it to pivot.
In my simple mind, that may be my problem. When I installed the nut, I left it loose until I had everything lined up. I don't think I tightened it up.
I have to head to Tucson this evening. When I get back after Labor Day, I'll check the lathe over.
Thanks again for the advice.
I appreciate this forum very much. No one laughed out loud, or threw rocks.
 
Mr. Bemnychree, I saw that stop on one of Tubalcain's videos I believe.
Between that device, and introducing an indicator as someone suggested, I should be able to get a better handle on knowing where my cutting tool is.
 
I haven't seen this mentioned before. In threading, you've made one pass, you want to back out, turn the cross slide counter clockwise. the first part of the turn takes out the backlash. So if you have a quarter turn of backlash, the cross slide doesn't move until that quarter turn has been accomplished. Then you move 3/4 turn and you're out of the cut. Adjust your compound for another pass. .005 or whatever. Then return your cross slide to 0 or your stop, or what ever. The back lash is gone once you move it one quarter turn.
Hope this helps.

A positive stop on the cross slide in a welcome solution when threading. Having seen the above illustrations I'm going to have to make one.
 
I dont think your tool should move back when you start cutting if that is what you are saying... something must not be tight or worn.
 
I made these out of aluminum for my two South Bend lathes. 15" on the left and 13" on the right. I like a nice, positive stop when threading. Really cuts down on the time. Work great!

Ted
IMG_20180824_185513.jpg
 
After explaining one type of threading stop with the swinging stop bracket, I decided to make one for my small Monarch lathe; the pics show it completed.

lathe stop 001.JPG

lathe stop 002.JPG
 
Here is a carriage stop I made for my 14 x 40 Jet

EDit. This is not a carriage stop but a cross slide stop!! I tried to change the original text, but it keeps coming back as originally posted - sorry
A7847D45-C392-4E4C-9627-7311C478B876.jpegC8C41DA1-4686-4FAF-A654-13B673FED713.jpeg6346B401-4294-44CC-AF7E-80C1EBD1143A.jpegCE2A2B8A-9C6C-4EFF-8CD7-FFCB51291BFB.jpeg6346B401-4294-44CC-AF7E-80C1EBD1143A.jpeg
 
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Here's a picture of my 13" SB setup to cut a right hand thread. There is a small threading tool in the holder, but it's hard to see in this picture. The compound is set at 29 degrees. My dials measure on the diameter not the radius like the older SB lathes. Moving the dial in 0.010" actually only moves the tool 0.005". When taking a cut, I move the carriage back to the positive threading stop in the picture. I move the compound in for the next cut. When taking the cut, all the cutting forces are on the left side of the threading tool (the leading edge). You should not see your tool move backwards because all the slop is taken out of the lead screws in the cutting direction.

Moving in 0.015" is a heavy cut for threading! Correct me if I'm wrong, but does the dial on your older SB work of the radius like my older SB lathe does? If so, that's a LOT heavier cut than what I would take on a small thread size. At work, I've threaded 6" diameter screws and might have taken a cut like that then, but not on a screw 1/2" or so in diameter.

If you are doing things correctly and the tool is still pushing back, not cutting on some passes and then taking a heavy cut on the next, I would check the grind on your tool for proper clearance. The coarser the thread, the more clearance you will need. On a coarse thread, the tool is moving towards the chuck fairly fast and if you don't have enough clearance on that front cutting edge it will drag until you build up enough pressure and then it will cut hogging all that metal off from the pressure it's built up. I really learned this while cutting a coarse, double lead screw for a heavy duty vise. I had to grind the tool with a LOT of clearance so the tool would cut properly.

Also, make sure your cutting tool is set right on center height of your lathe, not too high because this could make the tool rub on the clearance as well as not giving you an accurate 60 degree profile.

Ted

13 SB set up to thread.jpg
 
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