Help with Identification and Restoration of South Bend Lathe 420-YN

[Inquisitivan]

Hello all. This is my first post. I would like to thank everyone on this site as it is truly a wealth of knowledge. I have recently aquired a South Bend lathe. This was gifted to me by a friend. I have been doing extensive searches on the web and cannot seem to find much info on this particular lathe. The model is 420-YN. I don't like assuming things, so please correct me if I am wrong.

1. This is a early lathe that was made before the popular 9 inch lathes?
2. This lathe will be more similar to the "Junior" series of lathes?
3. Parts for the newer 9 inch lathes will not fit this version?

The lathe appears to have been modified. Several parts are missing, spindle gear, change gears, forward/reverse tumbler...am I missing anything else? My friend who I aquired only used the lathe for turning projects. I however, if possible, would like to safely use the lathe for threading as well as creating my own metric shaft size pulleys. I apologize if this post is asking for too much info at once! I'm just trying to figure out what I have first and then work on the availablity of parts. Any help is greatly appreciated!

 

[johnoder]

Its a "toolmaker" from the thirties.

See Mr. Wells catalog 94

The SBL Workshop

documentation and information on South Bend Lathes

www.wswells.com

 

[john.k]

Also note there is an electric motor unit geared to the feed shaft ,so its electric feed ...........you may be able to use the electric feed to cut threads with suitable controll unit.

 

[kitno455]

John's got it- a 1935 Series 20 Toolmaker. It is an interesting development in South Bend's response to the great depression. In terms of features, they are very similar to the later 9" workshop, but I'm not sure how much interchangeability you have in parts. If you can find a reverser that fits, metric threading will be easy with the right gears.

The power long feed assembly will be pretty useful, so I would not entirely discard it. But it could be redesigned so that it is mounted to the table and you drop the banjo gears down to engage with it.

allan

 

[jmm03]

I wonder if that was the original banjo and gears modified to it's existing location?

 

[Inquisitivan]

Thank-you all for the help with identification! I have just a few more questions. Please forgive me if this sounds silly but....

What if I was to substitite the current gearmotor with a stepper motor running off an arduino so that I could set the lead screw at a precise RPM?
Does anyone have info on the RPM's at which given thread is cut? I have a VFD laying around to control the spindle speed...

Again, forgive me if I'm missing a critical element of how these lathes work. If I would modify anything on the lathe I would be sure to make the changes reversible.

Also...the banjo is a "v" shape...not sure if that is original to this machine...?

 

[hudstr]

You can definitely use a stepper or servo to drive the lead screw. The term would be Electronic Lead Screw or ELS. If all you do is add a stepper to what's there currently, you could use it for power feed, but if you wanted to do threading you would need to add an encoder to the spindle. If a spindle bogs down from a cut, the lead screw also needs to slow down to maintain the correct thread pitch. You also need to know where exactly in a rotation the spindle is to stay in the same thread groove from the last pass.

The banjo is the cast piece that looks like an upside-down v where the feed motor is connected to the lead screw.

 

[Inquisitivan]

Yes! Encoder on the spindle. Now It's obvious for me to see the reason for the gears, to keep the lead screw feed proportional to the spindle speed! I will get started on the project. I think going the ELS route will be far easier and less costly than if I was to try to find all the change gears for this machine.

 

[johnoder]

Yes! Encoder on the spindle. Now It's obvious for me to see the reason for the gears, to keep the lead screw feed proportional to the spindle speed! I will get started on the project. I think going the ELS route will be far easier and less costly than if I was to try to find all the change gears for this machine.

"to keep the lead screw feed proportional to the spindle speed! "

Has nothing to do with speed and everything to do with RATIO between spindle and lead screw for that particular thread pitch

 

[animal12]

Keep us posted oh how you go about your ELS . There's a few group.io for a ELS

E-Leadscrew groups.io Group

"ELS" - Electronic Lead Screw — is an alternative to full CNC for simple bench lathes — especially those lathes which do not have a "Quick Change Gear Box". For such lathes, it would be useful to have a cheap method of sychronizing spindle speed to lead screw speed. If this can be realized...

groups.io

AtomicELS groups.io Group

Discussion and development of Jon Bryan's Atomic Leadscrew project

groups.io

Clough 42 on youtube is another & there's another , google Russian ELS & it should pop up .
good luck
animal