Atlas 10D lathe. Modifying lead screw for longer bed? LONG STORY!

[Quick Cal]

I might have a work around just want to confirm it with you guys.

I just got a 42'' bed to replace my worn out 36'' bed. I grabbed the only 5/8'' lead screw the guy had. It's 5-1/2'' longer than my original so I thought it was the correct one. But it comes up 1-1/4'' short on the new bed.. Dammm!

I think the problem has something to do with if there was a quick change gear box? Not sure. I'm guessing. All I know is it's too short and I don't want to buy or make a lead screw if I don't have to.

Clausing told me the proper lead screw for a newer 42'' lathe is 41''. They will sell me one for $400. There has to be something different between the lathes. This new lead screw I just got measures 39-1/4''. There is one on ebay with this measurement. The guy says it's for a 48'' bed. But hasn't replied back if there was a qcgb or not. I don't know how accurate his info is?

Here's my lathe showing the gear box.



Here's the new lead screw on the new bed showing how short it is.




So here's my idea on how to make this lead screw work. Just looking for any "Gotcha's". Like the carriage will interfere or something?

If I move the lead screw bearing over to the left I can use the existing left hole for the right bolt on the bearing. But this butts the lead screw in tight on the left head stock end and no room for the thrust washer next to the bearing. Also, the gear box lever won't shift to the right.



I would need to drill a new left hole. There would be a little bit of the bearing plate not supported shown by the black marker. But I think it would be ok? Or I could add a shim under it maybe?




I discovered the shift collar in the gear box was not allowing the lead screw to go over far enough to the left because the key way slot was not as long as my original., this was also not allowing the lever to function properly. But it would be easy enough to cut the key way longer? Then EVERYTHING would work, I think,,,lol. I'm not sure if this an issue or not. But if I can get the right end to work like I want, the lead screw will not be going as far over to the left by about 3/8''. It will come up short from bottoming out in the head stock end. But there is still a lot of engagement into the left end gear. I'm hoping that will be fine?

New screw on bottom.





The only permanent modification will be the extra hole in the bed at the right end. And a longer slot in the lead screw. I'm certainly open for suggestions. You guys see anything wrong with this plan,,,,lol. Thanks for any input.

 

[silence dogood]

I don't have an Atlas lathe, but I notice that about 2" of thread on both sides of the lead screw are not used at least on my lathe. So, you may be good. My concern is lineup it carefully, so the carriage won't bind.

 

[Quick Cal]

I don't have an Atlas lathe, but I notice that about 2" of thread on both sides of the lead screw are not used at least on my lathe. So, you may be good. My concern is lineup it carefully, so the carriage won't bind.

Drilling the new hole is going to be the hardest part. The center of the hole is right on the edge of a casting line where it steps down. I guess I can just try to grind it flat there so I can center punch for my hole. If the hole is off a little I can just make the hole in the bearing bigger.






If you look at my first pic above you can see where the original threads stop. I will be gaining about 3'' of threads with the new screw. I've barely used this lathe so I don't know how it works. With the original screw, if I was power feeding toward the chuck, could it crash? Or would it run out of threads and stop. Maybe just crash the lead screw before hitting the chuck?

I wonder if I could/should put some kind of stop collar on the new screw? Or is it not necessary?

 

[GrifterGuru]

You say you might grind a flat to allow straight drilling..

Can I counter by suggesting making a drilling jig with a flat face with a plate plate behind to match the step in the casting? Make it so it can be bolted using the R/H bolt hole and it will be less likely to move about when using it as the jig it is intended to be.

Re the leadscrew. As a secondary option, is there a chance you could make a short extension for the gearbox end that you can drill tap, screw into place, then machine the keyway slot into it? Heck, it may take time, but you could file the slot into it by hand. It would seem the easier of the options out there and avoid modifying the bedway. If you could braze or weld the proposed L/S extension to fully secure it, that may help longevity.

 

[Quick Cal]

You say you might grind a flat to allow straight drilling..

Can I counter by suggesting making a drilling jig with a flat face with a plate plate behind to match the step in the casting? Make it so it can be bolted using the R/H bolt hole and it will be less likely to move about when using it as the jig it is intended to be.

Re the leadscrew. As a secondary option, is there a chance you could make a short extension for the gearbox end that you can drill tap, screw into place, then machine the keyway slot into it? Heck, it may take time, but you could file the slot into it by hand. It would seem the easier of the options out there and avoid modifying the bedway. If you could braze or weld the proposed L/S extension to fully secure it, that may help longevity.

Great minds think alike,,,lol. I tossed and turned all night thinking how I was going to drill the new hole. I settled on using a piece of bar stock to make a drill guide. But honestly I didn't think of using the right hole to keep it from moving. Great idea.

Not sure how I'm going to flatten out that edge were the new hole is going to go. I only need to remove about 1/16 thickness. Yes I could just use a die grinder. But that might look messy. It would suck if I slipped and put a scratch all the way down the bed,,,,lol. I could do it if I had too. But I did have another idea that may or may not work. As long as I'm making a drill guide I thought I could just make the hole the correct size for an end mill and just flatten it out that way. Then use a center drill to start the new hole. Only problem might be will a cordless, or electric hand drill turn the end mill fast enough to cut? Like I said. I only need to remove about 1/16th.

I don't think the left end is going to be an issue at all. I'll cut the slot to match the original. I've read the free play is set at the right end and the left end lands where it lands. I don't think it's supposed to jam in tight anyway?

 

[GrifterGuru]

In all honesty, were it me, I would go with the L/S extension as the easier, less stressful, less risky option.

As to an endmill in a drill, It may work, it may not, that is the risk you take.

Re the drilling jig, why not make it long enough to bolt to BOTH the existing holes for extra rigidity? Only realised that after re-reading my original post.

 

[Quick Cal]

In all honesty, were it me, I would go with the L/S extension as the easier, less stressful, less risky option.

As to an endmill in a drill, It may work, it may not, that is the risk you take.

Re the drilling jig, why not make it long enough to bolt to BOTH the existing holes for extra rigidity? Only realised that after re-reading my original post.

Oh wait. I think I didn't understand what you meant.

So the right end comes up 1-1/4'' short. I think you are saying insted of doing anything to the right end just add that 1-1/4'' to the left end?

 

[GrifterGuru]

Oh wait. I think I didn't understand what you meant.

So the right end comes up 1-1/4'' short. I think you are saying insted of doing anything to the right end just add that 1-1/4'' to the left end?

Exactly that. Add the 1-1/4" to the left hand end of the leadscrew. It is certainly the easier, less stressful option.

That then means no mods to the bedway, no new holes, no stress about drilling the bed either.

It also means that you can use the lathe itself to machine the extension, as well as to drill the end of the leadscrew before tapping it for the extension to be screwed into place on the end, providing the leadscrew will fit through the spindle bore...

 

[Firstram]

Exactly that. Add the 1-1/4" to the left hand end of the leadscrew. It is certainly the easier, less stressful option.

That then means no mods to the bedway, no new holes, no stress about drilling the bed either.

It also means that you can use the lathe itself to machine the extension, as well as to drill the end of the leadscrew before tapping it for the extension to be screwed into place on the end, providing the leadscrew will fit through the spindle bore...

This is the way!

 

[Quick Cal]

Exactly that. Add the 1-1/4" to the left hand end of the leadscrew. It is certainly the easier, less stressful option.

That then means no mods to the bedway, no new holes, no stress about drilling the bed either.

It also means that you can use the lathe itself to machine the extension, as well as to drill the end of the leadscrew before tapping it for the extension to be screwed into place on the end.

Well it depends on who's getting stressed,,,lol. Drilling the new hole I can do myself stress free.

I have a friend with a full machine shop. He says I'm free to do what I want up there. But I don't know what I'm doing. It stresses me to no end worried about tearing up his machines. And it's hard to get him in the mood to work on "My old junk" as he calls it,,,lol. But he will if he has time, which isn't very often. That's why he tells me to do it.