South Bend 9" model 405 Lathe - Refurb / Restoration / Upgrade

[mr95gst]

I found an ad on craigslist for a $100 South Bend lathe. It had no pictures, but I bought it sight unseen. I figured at $100 it was worth the risk. When I picked it up that afternoon, I found out it was the sellers Dads and had been sitting in a barn for at least 20 years. It had significant rust and the apron was broken into 3 pieces. The head still moved but everything else was stuck. I initially thought it was a 9" model C but I later found out it was a model 405 with a 4' bed. The serial number looks like it was manufactured around 1935. Once the excitement of the purchase wore off, I began to have serious doubts. I figured I might be able to salvage some of the pieces, but most of it would be a lost cause. Spoiler Alert: I got the entire thing working again.

This is what I started with:















I started by disassembling, degreasing, electrolysis for rust removed, and a lot of hand scrubbing.











Then priming and paint:











Next I started reassembly:





I needed a bench to mount the lathe so I took a break to do some wood working. The top is made from pine 2x4s and the legs are 4x4s.





The original motor and drive assembly was lost at some point years ago. When I bought the lathe it came with an replacement AC motor and a horribly put together tensioning system. I decided to remake something out of tube steel that looked a little more like the original South Bend configuration. I decided to go with a DC treadmill motor and a variable speed DC drive. With the DC motor, I don't need step pulleys and I didn't have to configure a complex belt tensioning device. I cast the motor mount and motor pulley from aluminum scrap.









After running the lathe a bit, I noticed the motor was getting hot. This is a 12v motor and shroud I made that slips onto the back side of the motor.





This is a junction box that houses the on/off switch, speed controller, fan power supply and tachometer.




This is the tachometer sensor and mount. The rear pulley is only slightly larger than the pulley on the spindle. That means the spindle RPM is only slightly faster than my tachometer reading. I was really just trying to get a ballpark reading.





The lathe came with an independent 4 jaw chuck. I got fairly proficient with it, but I wanted a self-centering 3 jaw. The problem with a model 405 is that the spindle thread is 1-3/8" -10. No one make an adaptor or back plate. To my knowledge South Bend was the only company to use that thread on a spindle and they only did it for a couple years. I used decided to use the small back plate from the 4 jaw to make an adaptor. I cast a 6.5" disk from aluminum and turned it to accept the old back plate on one side and the new 3 jaw on the other.



















This is the lathe all finished up. I have done several hours of turning on it at this point. I have mostly done aluminum. So far it has exceeded my expectations. Everything is solid and the surface finish is great. South Bend produced a quality and capable machine 80 years ago!











Here is a piece of cast aluminum I turned before I had the 3-jaw chuck.

[ragsflh]

thanks,looks great

[Wmrra13]

Nice work! I'm very impressed, particularly with the VFD drive system and 3-jaw mounting solution - even the bench is really nice!
Please show us more of your foundry techniques.

Cheers,
Tyler

[pfredX1]

I can't believe they still wanted $100 for that lathe in the shape it was in. But hey you got it going again. I'm surprised they even knew it was a lathe. I can see why they didn't post any pictures of it too.

[olderdan]

Great restoration job mr95gst, if my SB 9B is anything to go by you will be well rewarded these are quality machines.
It looks as though all that muck on it did you a favor in the end.
I notice a lack of tumbler reverse so I can recommend a reversing electric leadscrew drive (No 1 mod for me).
Regards
Olderdan

[tonyfoale]

I notice a lack of tumbler reverse so I can recommend a reversing electric leadscrew drive (No 1 mod for me).
Regards
Olderdan

Alan,
Are you talking about a synchronised leadscrew drive that would enable screw cutting or a free running system just for turning/facing feed?
if synchronised, how are you doing that. I ask because I am thinking of doing that and there is no point reinventing the wheel.

Some years ago I bought a lathe that looked to be in bad rusted shape, but it turned out that it had spent years unused in a corner near the grinding area before being put out to pasture. The rust was mainly on the old grinding swarf and so when cleaned up there was little rust on the machine. Here are some before and after shots.

[olderdan]

Tony,
I am no help to you on this as my leadscrew drive is just for plain turning only.
Having said that I find it a vast improvement as its variable speed and adjustable during a cut.
I used a new golf cart 12v motor and gearbox powered by a battery charger, to be honest I do not have the knowledge to create a synchronised system.
That lathe you restored is one solid piece of machinery, and a very nice job you made of it.

[tonyfoale]

Tony,
I am no help to you on this as my leadscrew drive is just for plain turning only....., to be honest I do not have the knowledge to create a synchronised system.

There are many ways to do it. The easiest would probably be to put an encoder on the spindle which will tell you where that is. I am actually waiting for an encoder to arrive and I attach a pic. of the mounting that I have made for it. Then use a stepper motor on the screw, or geared down to the screw. Then it is only a matter of training some electrons to feed steps according to the gear ratio "spindle to screw" that you need. An Arduino with a stepper motor shield could run the electron circus at very low cost. Although this is probably the easiest way to do the job, it is not the best. If you use the half nuts for screw cutting you still have the need to engage them manually at the correct moment and you still have the reversing out problem when cutting metric threads with an inch lead screw and vice-versa.
One better method using the same basic hardware would be to define a "home" position of the saddle, which the control system would find on each startup. Then the position of the saddle is always known relative to "home", as long as you don't open the half nuts. If you accept not opening the half-nuts then you might as well replace the nuts and lead-screw with ball nut and screw (not overly expensive now). The downside is that you are then prevented from moving the saddle manually so you add a pulse wheel (see pic) to the apron.
Now that you've got that far you might as well do the same to cross slide and then you have a full CNC lathe.
Personally I don't like trusting steppers to never miss a beat and I prefer using servo motors and linear slides for position, but the cost is higher than the first option and fitting the slides is not always easy.


Pulse wheel.


Bracket for rotary encoder. Smart Alex will note that it prevents long stock being used. That bracket was designed to hold an encoder with none of the backlash or flex associated with a belt driven unit. This is for a specific accurate measurement task and not for general lathe work.

That lathe you restored is one solid piece of machinery, and a very nice job you made of it.

I hadn't much of a workshop for 20 years after I moved from England to Spain, but 10 years ago I came across the one pictured, but no sooner had I got it up and running than I got a job offer out of the blue from Segway and I went to live in the US for 3 years. Over there I acquired a nicer lathe, albeit smaller, a CNC Bridgeport mill and a bunch of other stuff which I shipped back. Workshop space was at a premium so I got rid of the big lathe. A decision that I regret on the odd occasion. Although it cleaned up nicely, it had had a hard working life and the bed was heavily worn, so precise work had its problems.

[Wmrra13]

Hey Tony,

Coincidentally, I'm the process of restoring/setting up that same Asian 12x36 lathe. Where do you find parts for yours?

Also, I'm a bit out of the loop now but, I was club level road racer and subscriber to RRW&MT for many years and always enjoyed your articles. At least the parts I could understand....

Cheers,
Tyler

[rossbotics]

That's a great job you did there on the restore, I myself have 4 older metal working machine tools that I have restored back to there originality, I'm from the old school and this is the kind of equipment I was taught on, I personally do not want anything but this kind of equipment in my shop, this stuff is indestructible, this summer I'm going to restore my 6913 Clausing lathe.
Love the back plate casting and VFD, did it have all the change gears?

Here is a link to my shop and some machines I restored
https://rossbotics.wixsite.com/machiningtechniques


You did a great job, keep up the good work