South Bend Clutch Repair

I recently picked up an old 13 inch South Bend lathe and have been working to get it up and running.  Here it sits, just off the trailer and inside the garage.. yay!  The first thing I noticed was that the clutch handle swiveled freely (not meant to work that way).

south bend lathe

The clutch worked but not well, and the set screw that locks the handle from rotating was fully set.  After taking things apart and pouring over the parts breakdown illustrations, I came to the conclusion that I must have inherited some hybrid assembly that was perhaps made up of more than one design.  Regardless, I needed something that would function like a pin and a key at the same time, so I made one on the Taig micro lathe!

Here you can see the clutch handle and set screw underneath the apron.  Pulling the handle out engages the clutch which starts the power feed.  Some of these lathes have a star shaped handle that is turned in order to engage or disengage.  This model uses the lever and allows for adjustment of the angle of the handle via set screw and collar.

south bend apron  south bend clutch lever set screw

The set screw was fully tightened and the handle was still free to rotate.  Meanwhile, the clutch assembly wasn't fully engaging.  After removing the apron and disassembling, it was obvious that something was missing or misconfigured.  The collar shown here presses up against a thrust bearing which allows it to remain stationary while the mechanism inside rotates.  A shaft that you will see later is what attaches to the handle and this shaft is supposed to be coupled to the collar.  The collar has a key way while the shaft has a hole.  I decided to make a small part from key stock that would fit both the key way and the hole.

clutch adjustment parts

 

Below is the key stock that I started with.

key stock

 

I mounted the stock in the four jaw chuck, off center so that only one side would need trimming.  Turning down approximately half the stock was quick and easy with a facing operation.

turning key stock in for jaw chuck  key stock four jaw chuck operation complete

 

Here you can see the turned piece.  Next I needed to trim off the end, which could have been done with a file, hack saw, or the milling attachment.  I chose to use the Taig mill.

key stock turned down

 

And here is the setup in a small vise.  I took light cuts to prevent the part from slipping.

milling extra length

 

After milling, this is the finished part and the rough dimensions I had sketched up.

completed key stock pin

 

Here you can see the shaft with key-pin combo installed.  I still haven't seen what the intended design was, but this works fine.  The key isn't put under any real loads and only occasionally is under light load when adjusting the clutch handle angle.

assemblying the part  key stock pin in clutch shaft

 

The collar slides on with no interference.  Note that this new part has to be installed after installing the shaft with clutch disks from the other side.  I tried a cotter pin, inserted and then bent and trimmed, but nothing I had on hand could make the sharp bend while providing a reasonable fit.  If anyone out there knows how this assembly is supposed to stack up, I'd be interested to learn about it.  Just use the contact form on this site to shoot me an email.

ready for reassembly

 

Here is the final installation with a thrust bearing washer shown clearing the key-pin part.

new part assembled in apron  thrust bearing clears

All is working well with the clutch assembly now.  I cleaned out many metal shavings and replaced the felt oil wicks.  Something to note about having a bigger lathe, is that it has not reduced my use of the smaller Taig micro lathe.  Machining this tiny key stock on the South Bend would have been quite difficult.  The four jaw chuck that I have for the larger South Bend wasn't designed to grip tiny parts.  The larger radius on the tips of the jaws would probably mean I would have had to start with larger stock and then mill down the other half afterwards.  Also, machining very close to the jaws on a larger lathe is nerve racking.  In other words, I don't think anyone has to worry about making a Taig lathe purchase and then having buyer's remorse if they decide to go bigger.  While in my shop, the Taig lathe will still be the right tool for many machining tasks to come.  Happy machining!