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

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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
 

Comments

#2
Is it the backlash that is making it hard for you to do? If so , if you turn the handle to the right to get to your point of cutting then after you run the cut you can turn the handle to the left to back the tool out. When you move the tool back to the starting point make sure you turn the handle to the right again which will take the backlash out again and you should be able to go back to your first point of cut and add the extra to cut in further. Hope i explained it well.... Warren
 
#3
Cross slide is used to retract the compound slide. Compound slide is used to cut the thread depth (not all at once pls). Snug the cross slide gibs, if the cross slide & compound dials has a set screw, use it to hold your zero. Fenner, Abom79 & Oxtools have excellent threading vids. No worries, we all have to start somewhere.
 
#4
Just a hobbiest, can you put felt tip mark on the cross slide and it's mating surface and go past the mark and then turn it back to the mark matching the dial to the zero?
 
#5
If the front face of your cross slide has a tapped hole in it, you can make a screw to fit it with a threaded collar outboard of it and a stop bar to fit the dovetail of the male dovetail that clamps to the dovetail via a detachable dovetail on one side with a bolt through from the end to clamp it up and a hole through the center to accommodate the threaded rod attached to the cross slide, this is a stop to limit the amount of travel of the cross slide when threading; most lathes had a device like this, but most got lost (mine did). They would be an easy thing to make. I will see if I can get a picture of one and post it later. Having lots of backlash makes it a bit harder to back out and keep up with where you started, especially with very coarse threads are being cut, keeping track of the number of turns necessary to clear the threads.
 
#6
You know, I have not analyzed it, I made an assumption. I make a cut, make one full revolution to the left, move saddle, return the cross slide back one full turn to the right. By this action, I assumed I would not be in the same spot taking the backlash into consideration.
So you are saying it works both ways? One full turn out and back in will get you back to the same exact place?
Another study on my part, when I move the compound in (set at 29.5) I am moving the compound to the to the opposite side of the pressure of the screw. Meaning when I make a cut, the tool is pushed back to the opposite side of the screw.
Am I making any sense?
Regarding gibs, I have them as snug as I can before binding, the screws and brass are new.
I have watched plenty of videos, Mr. Pete, Tom's Techniques, Oxtools etc. The videos are extremely helpfull.
My threads are of good quality, clean cuts, I grind HSS, the thread gauge works flawlessly as long as I go back to the same number each time.
I am getting close, I just struggle with the exact depth I am attempting to cut. I can move in .015 and I only make a very light cut. Next time, I move in .015 and the cut is a bit too deep??
Practice and observation is needed on my part. I'll get it.
Thanks guys.
 
#7
If the front face of your cross slide has a tapped hole in it, you can make a screw to fit it with a threaded collar outboard of it and a stop bar to fit the dovetail of the male dovetail that clamps to the dovetail via a detachable dovetail on one side with a bolt through from the end to clamp it up and a hole through the center to accommodate the threaded rod attached to the cross slide, this is a stop to limit the amount of travel of the cross slide when threading; most lathes had a device like this, but most got lost (mine did). They would be an easy thing to make. I will see if I can get a picture of one and post it later. Having lots of backlash makes it a bit harder to back out and keep up with where you started, especially with very coarse threads are being cut, keeping track of the number of turns necessary to clear the threads.
I was hoping there was something like what you are describing.
Thank you.
 
#8
Here are some pics of a cross slide stop for threading the first pics are of the dovetail type, the last two are of another type where the stop rod is at the front left hand of the cross slide and another tapped hole on the front left of the carriage just below the cross slide, which mounts a slotted link that the stop rod engages with a adjustable stop nut, the link swings out of the way when not in use.
 

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#10
You know, I have not analyzed it, I made an assumption. I make a cut, make one full revolution to the left, move saddle, return the cross slide back one full turn to the right. By this action, I assumed I would not be in the same spot taking the backlash into consideration.
So you are saying it works both ways? One full turn out and back in will get you back to the same exact place?

You can't base it on turns if you want precision. You need to use the dials or an indicator. Set the cross slide where you want it, zero the dials or indicator. Now you can get back where you were to the limits of the graduations. Note that for the dials to be accurate, you need to move only in the same direction the entire time. You can't spin back to get there, you have to take up the backlash, move out a little, then do the same going the other way and stop on the mark.

One thing that might come up with a lot of backlash is if you need more than one turn to take it up. Then you have to remember to move 2 turns + go to the mark. You could practice with a dial indicator on the cross slide so you can see exactly where you are the whole time.

There's nothing wrong with building a stop as well, but make sure you know how to hit the right spots using the dials.

For depth, since you're using the compound you are at an angle and the graduations don't tell you exactly how much you're cutting. I believe there is a calculation to figure it out, but just use a gauge, or if you want to-spec threads, a thread mic or measurement wires. If the issue is more about depth of cut, you might have deflection in play as well.
 
#11
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
 
#12
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.
 
#13
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.
 
#14
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.
 
#15
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.
 
#16
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
 
#17
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.
 

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#18
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.jpeg C8C41DA1-4686-4FAF-A654-13B673FED713.jpeg 6346B401-4294-44CC-AF7E-80C1EBD1143A.jpeg CE2A2B8A-9C6C-4EFF-8CD7-FFCB51291BFB.jpeg 6346B401-4294-44CC-AF7E-80C1EBD1143A.jpeg
 
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#19
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.
Agreed, that’s why I am inquiring to the group. Something just ain’t right.
 
#20
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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