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

 

Well Ted, and Benmychree, I think your cross slide stops are what I need. I have a hard time knowing with any precision where I am returning my cross slide to when threading.
Small dials, poor vision and backlash add up.
I bought this quality 60 degree dovetail cutter. I’ll give it a shot.
I plan on making a stop for the slide to positively return to zero so the compound can do the thread cutting with confidence.

 

That's good that you bought a dove tail cutter because they can certainly come in handy. Here's a solution for those, who like me at the time when I made my first stop for my 15" SB, don't have a dove tail cutter and don't want to buy one. Just use a smaller end mill and cut the 60 degree side undercutting the top surface.

Ted

 

Hi Guys,

FWIW I always try and thread away from the chuck ! I run the lathe backwards and plunge straight in with a carbide threading 60 degree insert.
I don't disengage the half nuts, preferring to wind back to the thread start by hand. I've never had a problem with backlash, even though I know that I do have some. It also helps to cut a groove, not just for tool runout, but for some clearance when running up to a face when the work is finished.


This M30 by 1.25 threaded collar was done this way. The runout groove allows the collar to sit right up against the mating face.


That thread is 4-48. I'm threading an elephants foot here. You can get a good view of the tool holder and carbide insert.

 

Why not just use a mag base dial indicator set your zero and return to zero every time? You can use that concept on saddle, cross slide and compound if wanted.

 

Why not just use a mag base dial indicator set your zero and return to zero every time? You can use that concept on saddle, cross slide and compound if wanted.

Yep, you sure can use an indicator and I've done so with machines that don't have positive stops before. For me though, and this is just personal preference, I like the feel of the positive hard stop since I always have my left hand on the cross feed crank ready to quickly withdraw the tool if something doesn't act quite right while threading. I also always have the hand crank at the 9 o'clock position so it's automatic what I have to do if I get into trouble... just push down quickly! With the positive stop, I know I won't accidentally move the crank to feed the tool in slightly while my hand is riding on the hand crank. I can feel it up against the stop the whole time. All the lathes at work when I was learning had built in adjustable hard stops and this just feels natural to me.

A lot of different techniques work... you just have to find the one that works best for you.

YMMV,
Ted

 

Im taking the good advice you all have provided.
I am making a stop. I like the dial indicator idea also, I need to learn to use these small dials anyway.
A dial indicator will tell me where I am, the stop will give me the accuracy I need to move the compound in .005” per pass.
Threading from the chuck out is something I’ll have to play with.

 

Hi Janderso,

One of the issues with hard lathe stops is if you hit it under power, you are likely to cause damage to the lathe. Probably a shear pin somewhere, although I've seen a picture of a lathe with a stripped gear after hitting a hard stop under power.

This is one reason I thread the way I do ! No chance of hitting the chuck, saddle stop or anything else. OK cutting metric threads may mean keeping the half nut engaged and winding back. I made a spindle handle to do that.

 

Made a big step forward today. I made a cross slide stop and cut some 1/2" 13 TPI. Best threads to date for me.
The stop really helped me stay on top of the compound feed in accuracy. That created an environment for good quality.

 

Hi Janderso,

That looks like a very acceptable thread ! Did you cut it towards or away from the chuck ?
I like the crosslide stop as well, very nicely finished.

I've no room on my lathe for anything like that, but I did build a dial gauge mount so that I can accurately measure crosslide movement.
However I don't use it much, since the dial on mine is spot on 1 thou per division and a known backlash amount of less than 10 thou

 

I did it the old fashioned way, but, I am going to try it your way.
I did grind the bit myself though, the threads are clean. The last time I tried carbide the threads looked like they were torn rather than cut.
I am very pleased at how this went.
I do get a bit anxious when I open the half nuts, what if they stick or bind?
Armageddon!