Getting an old lathe tight again, HELP

[Robert Haas]

I acquired an old South Bend lathe, it is a very simple pre war unit. The head stock and tail stock are rock solid. the problem lies in the cross slide. the threaded rod and the cross feed nut have way too much play in them.

Is there anyway to get that slop out of it, I know less then nothing about lathes but I am a mechanic and I did take the sucker apart hoping to find some type of thrust bearing or other repairable option, and came up empty.


Any ideas?

 

[rlitman]

Threaded rod and nut? Are you talking about a lamppost toolholder? Or backlash in the leadscrew?

The cross slide is tightened by the gib screws. If you do not already have them, I suggest making sure that your gib screws have lock nuts.

The cross slide lead screw will always have some backlash. You always turn it inwards for cutting. Back it out at least as many turns as it takes to make up for the backlash (1-2), and then turn it back in to where you need. You can minimize this backlash by moving the dial, but you need some, so it doesn't bind.

 

[ttpete]

If it's excessively worn, the screw and nut will have to be replaced. That's what I did.

 

[DenisG]

If you know any local machine rebuilders, sometimes they can supply you with the parts. That's how I found and replaced parts on an old South Bend that I had. Sometimes you can find the parts on eBay, if you know what you're looking for. You might also check out the South Bend lathes users group on Yahoo and make contact with a source there. Here's another reference:
http://www.practicalmachinist.com/v...uth-bend-links-sources-parts-info-etc-129769/

 

[paulsomlo]

Is there anyway to get that slop out of it, I know less then nothing about lathes but I am a mechanic and I did take the sucker apart hoping to find some type of thrust bearing or other repairable option, and came up empty.
Any ideas?

On a prewar SB, there wouldn't be any thrust bearing. The newer ones with large dials had them.

You'll need to ID the source of the slop. It's either the nut, the screw or wear between one of the following interfaces; screw shoulder/bushing, graduated dial/bushing, graduated dial/handle.

If you pull the dial back towards the handle and lock it in place with the setscrew, does a space develop between the dial and bushing when you turn the handle? If so, you can shim it out.

Is the slop much worse in the middle, than at the extreme ends of travel? If so, suspect screw wear. If it's fairly evenly distributed, then look at the nut (and possibly the screw, as well).

You might go over to PracticalMachinist.com and register - this has been covered in the South Bend forum there many times, a quick search will tell all.

Here's a link that you might find useful as well, courtesy of Steve Wells:
http://www.wswells.com/crossfeed_screw/crossfeed_repair_index.html

 

[ttpete]

On a prewar SB, there wouldn't be any thrust bearing. The newer ones with large dials had them.

You'll need to ID the source of the slop. It's either the nut, the screw or wear between one of the following interfaces; screw shoulder/bushing, graduated dial/bushing, graduated dial/handle.

If you pull the dial back towards the handle and lock it in place with the setscrew, does a space develop between the dial and bushing when you turn the handle? If so, you can shim it out.

Is the slop much worse in the middle, than at the extreme ends of travel? If so, suspect screw wear. If it's fairly evenly distributed, then look at the nut (and possibly the screw, as well).

You might go over to PracticalMachinist.com and register - this has been covered in the South Bend forum there many times, a quick search will tell all.

Here's a link that you might find useful as well, courtesy of Steve Wells:
http://www.wswells.com/crossfeed_screw/crossfeed_repair_index.html

It's not too difficult to find. Just ease off the gib screws and grab the toolpost and slide it back and forth.

 

[Robert Haas]

the play is defiantly in the thread/nut interface. it is a ton, over hundred thou.

 

[Steevo]

Robert,
paulsomlo gave you great advice above, to which I can only add this:

Try over at
http://hobby-machinist.com/

The forums there are MUCH friendlier to non-professional machinists or garage machine owners than the guys at practical-machinist, who I have found to be "very elitist" and full of themselves, and seem to be above dealing with newbies.

The Hobby machinist forum has a sub-forum specifically for South Bend machines, and is full of very helpful folks (kinda the GJ of machining forums), who are always happy to assist anyone.

 

[Robert Haas]

Robert,
paulsomlo gave you great advice above, to which I can only add this:

Try over at
http://hobby-machinist.com/

The forums there are MUCH friendlier to non-professional machinists or garage machine owners than the guys at practical-machinist, who I have found to be "very elitist" and full of themselves, and seem to be above dealing with newbies.

The Hobby machinist forum has a sub-forum specifically for South Bend machines, and is full of very helpful folks (kinda the GJ of machining forums), who are always happy to assist anyone.

Thank you, heading there now

 

[spongerich]

.100 is high for backlash, but not necessarily terminal, just make sure you take it up before setting your dial. To repair it, I'd start with replacing the nut. They're bronze and do wear. They're also fairly inexpensive. If you still have excessive backlash, then you'll need to replace the screw too.

 

[paulsomlo]

There are three people on ebay making reproduction nuts for SB lathes, here's the one I'd go with: http://www.ebay.com/sch/tross96586/m.html?item=291687660771&hash=item43e9f07ce3%3Am%3AmrLBD-cEZOGbYD3t79uNBFQ&rt=nc&_trksid=p2047675.l2562

He can probably make you the screw, as well. If you want NOS, you might try emailing Ted, who used to work at SBL, [email protected], removing "deletethis" in the address.

How 'bout a picture of the lathe?

 

[mikegt4]

Robert,
paulsomlo gave you great advice above, to which I can only add this:

Try over at
http://hobby-machinist.com/

The forums there are MUCH friendlier to non-professional machinists or garage machine owners than the guys at practical-machinist, who I have found to be "very elitist" and full of themselves, and seem to be above dealing with newbies.

The Hobby machinist forum has a sub-forum specifically for South Bend machines, and is full of very helpful folks (kinda the GJ of machining forums), who are always happy to assist anyone.

The founder/owner of Practical Machinist owns a machine shop and started the forum to serve business owners and professional machinists. He makes it clear that he doesn't want hobbyists on his site hence the cold shoulder. There is a lot to learn by lurking there.

In addition to Steevos mention of Hobby Machinist there is also Home Shop Machinist and The Home Machinist, one if not both were started by hobbyists booted off of PM.
http://bbs.homeshopmachinist.net/forum.php
http://www.chaski.org/homemachinist/index.php

 

[My Old Tools]

Robert,
paulsomlo gave you great advice above, to which I can only add this:

Try over at
http://hobby-machinist.com/

The forums there are MUCH friendlier to non-professional machinists or garage machine owners than the guys at practical-machinist, who I have found to be "very elitist" and full of themselves, and seem to be above dealing with newbies.

The Hobby machinist forum has a sub-forum specifically for South Bend machines, and is full of very helpful folks (kinda the GJ of machining forums), who are always happy to assist anyone.

Steve, in general you are right, but the South Bend forum is very accomodating to newbees. The people are knowledgeable and some former SB employees hang out and have access to NOS parts.

 

[Robert Haas]

There are three people on ebay making reproduction nuts for SB lathes, here's the one I'd go with: http://www.ebay.com/sch/tross96586/m.html?item=291687660771&hash=item43e9f07ce3%3Am%3AmrLBD-cEZOGbYD3t79uNBFQ&rt=nc&_trksid=p2047675.l2562

He can probably make you the screw, as well. If you want NOS, you might try emailing Ted, who used to work at SBL, [email protected], removing "deletethis" in the address.

How 'bout a picture of the lathe?

The Screw on my lathe has a integrated gear on it. probably gonna be a pricey replacement.

 

[Robert Haas]

I have seen a couple complete carriage/apron assemblies on E-bay for older south bend lathes. how compatible are they from model to model?

 

[rlitman]

The Screw on my lathe has a integrated gear on it. probably gonna be a pricey replacement.

Sounds like you now have a lathe project now that you have a lathe.

 

[paulsomlo]

I have seen a couple complete carriage/apron assemblies on E-bay for older south bend lathes. how compatible are they from model to model?

I seem to remember that at one point, there was a casting change which may hang up the geared section. I wouldn't go in that direction, it has it's own set of perils.

Here's a link to Miller Machine, where $275 buys a new screw (w/gear) and a new nut: http://www.millermachineandfabrication.com/1.htm

I'd bet that's a good portion of what you paid for the machine, though.

The way this is typically dealt with is, you cut off the threaded section, turn or purchase a new threaded section, then drill/bore/ream and slip fit the new section to the old portion which still has the gear. If you scratch around steve wells website, wswells.com, you'll find examples of people that have done so. And I think it's been documented over on the SB forum of Practical Machinist. It may be beyond you at this point, but in a year or so, you may be ready to tackle it. And the lathe is still usable - maybe annoying, but usable.

Even if you don't register/post over on PM, you might do some searching on the SB forum there. There is a wealth of info, and I can pretty much guarantee that any question you may have, has already been answered there.

So where's those pictures?

 

[justanengineer]

The founder/owner of Practical Machinist owns a machine shop and started the forum to serve business owners and professional machinists. He makes it clear that he doesn't want hobbyists on his site hence the cold shoulder. There is a lot to learn by lurking there.

In addition to Steevos mention of Hobby Machinist there is also Home Shop Machinist and The Home Machinist, one if not both were started by hobbyists booted off of PM.
http://bbs.homeshopmachinist.net/forum.php
http://www.chaski.org/homemachinist/index.php

Nah, Don (Milacron) is simply a machinist turned machine tool dealer. He doesnt mind hobbyists, heck, the SB subforum on PM is mostly hobbyists who know little/nothing of machine operation or repair. Several of the other subforums are similar - mostly hobbyists talking antique iron and nobody cares if they ignore a few rules so long as theyre civil. There's only a few subforums where hobbyists need be careful on there, those that deal with modern machines/machining. Even a few teenagers get along well there.

The HSM bbs site and Chaski have both been around longer, HSM started naturally bc of the magazines. Don/Milacron is a member there and occasionally posts. PM was actually started bc of Chaski, quite a few folks didnt like how it was operated ~15 years ago so PM began. With that one as well there isnt any animosity and owners/mods are on both, its just an old simple disagreement.

The only forum I'm aware of that started bc of folks booted on other forums was the hobby-machinist site which was started by a member booted from PM, HSM, and Chaski for well over the top bad behavior, who subsequently spammed the **** out of those forums, copy/pasted entire threads from them into his own forum, copied popular usernames to make it appear popular senior members elsewhere were on his site, and a whole host of other nonsense which continues. Nope, I have no dog in that fight but I am an active member of several clubs, attend several model engineering shows annually, hate douchebags, and nobody I know in the hobby will touch that site with a 10' pole bc everyone knows the history.

 

[justanengineer]

As for the OP's backlash issue, I say learn to use the machine and make your own feedscrews and nuts on it.

 

[pbkelley]

My late 30's South Bend required a few washers to tighten up the cross feed screw. The Ebay manual on rebuilding a South Bend lathe that comes with the felts shows the process. I was able to get my backlash down to .010".

I also use a dial indicator for mounted on the crossfeed when I need to do accurate cuts.

 

[MushCreek]

I've made some quick 'n dirty screws out of acme threaded rod. Make sure you get left hand thread; I worked in a shop where they made their own parts and used right hand thread. You had to turn the handle counterclockwise to move towards the work. No one ever used that lathe after that.

Another wear point on old lathes is the threading lead screw on the front of the bed. The good news is that they generally wear out just in one small area. I cut the ends off, and flip it end for end, making new ends and pressing/pinning them on. Now the worn area is way out near the tailstock.