Clutch Not Engaging on South Bend 14 Lathe

I have owned a South Bend Lathe for a couple of years and was slowly learning to use it as I worked out a few issues. My electrician had the wiring out of phase and I finally got around to experimenting with the connections at my rotary phase converter. I got that sorted out and I don't have to run it in reverse to get it to cut properly.

I recently worked on troubleshooting the speed control and discussion here was very helpful. I was puzzled because the speed control worked when I tested it under power at the seller's shop. I finally figured out that during the trip in a trailer and locating it in my garage/shop, the gear on the small motor to move the Reeves pully became disengaged from the gear on the Reeves pulley. The speed control works but the tachometer on the headstock is not displaying the speed. The needle occasionally jumps to the right and returns to the left position.



The speed control does adjust the speed of the spindle. I use a laser hand-held tachometer to determine the speed. That is working, for now, so I'll get to the point.

The clutch to move the saddle under power will not engage. The half nut does engage and the saddle moves in the neutral position. If I engage either the longitudinal movement or the crossfeed with the toggle in the up or down position respectively, nothing happens

I have tried following the directions I found in a couple of maintenance manuals for South Bend 14 lathes that appeared to be similar to mine did not fix this.

The manuals state:

TO ADJUST CLUTCH

1. With allen wrench, loosen set screw "U" and turn lever clockwise until clutch engages in proper position. (see Figs 10-11). Clutch lever should not go beyond the perpendicular to the thrust collar "R".

2. Clutch lever should be just tight enough to stay engaged in a heavy cut. If clutch is too loose, repeat steps outlined above. If too tight, turn clutch lever counter-clockwise in steps outlined above.​

The clutch lever on my SBL 14 has the set screw "U" as pictured below. I have loosened it, however, when I turn the clutch lever, nothing happens. There does not feel to be any change in the tightness of the nut.[/INDENT]

Behind the headstock there is an electrical box and about the top left side there is a large coil that is used to adjust the tach so it is correct.
Check for contact. The manual describes the procedure for setting the tach. If lucky it is just a continuity problem.

If the engagement lever is screwed in far enough (CW), the lever cannot be pulled to the 'up-horizontal' position. If there is no change the apron may have to come off.
I'd tell you more but no longer have the manual.

Don't flip spindle direction forward-reverse. There is a special collet within the long tube attached to the Reeves Drive sheave. SB made the
collet keyway with square corners and then hardened the collet. The collet has very little material at the nose and that is where it will crack.
I made a replacement and had it hard chrome plated and ground back to size instead of being hardened.
That sheet metal bed puts a twist in the lathe bed - my opinion.
John

jhruska,

Thank you for taking the time to respond. I haven't had time to do any additional work on my SBL 14. Below is a photo of the electrical box on the back of this lathe.

jhruska said:

Behind the headstock there is an electrical box and about the top left side there is a large coil that is used to adjust the tach so it is correct.
Check for contact. The manual describes the procedure for setting the tach. If lucky it is just a continuity problem.

Click to expand...

The coil, variable resistance coil for lack of a better name is smaller than the one I worked on. Should work just as well but fine tuning the rpm in the meter may tricky as the length of resistance wire is shorter. Check the connections for the little transformer and see that they are tight as well as all the other leads screwed into the board. Power off of course
John

jhruska,

I'll check the transformer and connections. Thanks again.

Apron clutch...

The 14 has but a lead screw, (no separate feed rod) so it has to have a full length keyway in the lead screw to drive apron gearing for feeding. Naturally a key will be involved in this design. Such keys wear thin and then fail. Has that happened on this lathe?

johnoder has a good point about checking the the key.
I believe it is U-shape and hugs the left and right end of the worm that the drive rod goes thru.
ie: no key no engagement.
John

jhruska said:

johnoder has a good point about checking the the key.
I believe it is U-shape and hugs the left and right end of the worm that the drive rod goes thru.
ie: no key no engagement.
John

Click to expand...

When I engage the clutch lever with either crossfeed or longitudinal power feed I can't move the handwheel on the apron. Doesn't this indicate the clutch is engaging and further confirms what you're both saying about the key?

A further eyeball confirmation is the seeing by mirrors / good lights if the gear (or worm or whatever) on the lead screw turns with the lead screw when one of those feeds is engaged

Failure of that item to turn plainly says failed or missing key

Here is a parts diagram for a South Bend 14 that is from 1979. My lathe was purchased by a Houston-area school district in 1985, so it appears to be similar to the manual I found online.

The odd thing is that this SBL 14 doesn't appear to have much wear, all moving parts do not have visible damage or wear. Perhaps the key was sheared by misuse since it was originally in a school? Number 18, the "worm key", on the diagram makes sense to me now, but it seems like it would take a lot to damage that.

The question for you, since you say you have had the lathe for several years - has the feed ever worked? If you never tried it, I'll suppose the lathe's apron has been apart and put back together without that key - before you ever got it

I'll suppose its even possible that this disabling was decreed by school management - to make it more difficult for the "children" to maim themselves

exphiveoh said:

Here is a parts diagram for a South Bend 14 that is from 1979. My lathe was purchased by a Houston-area school district in 1985, so it appears to be similar to the manual I found online.

The odd thing is that this SBL 14 doesn't appear to have much wear, all moving parts do not have visible damage or wear. Perhaps the key was sheared by misuse since it was originally in a school? Number 18, the "worm key", on the diagram makes sense to me now, but it seems like it would take a lot to damage that.


View attachment 278483

Click to expand...

exphiveoh said:

When I engage the clutch lever with eithercrossfeed or longitudinal power feed I can't move the handwheel on the apron. Doesn't this indicate the clutch is engaging and further confirms what you're both saying about the key?

Click to expand...

If you have them would you post the other assembly drawings of the apron?
Here is the clutch group with a tweak:

The SB-14 as introduced in 1969. The Hi-Lo lever for spindle rpm is not present in the panel below the apron.

John

johnoder said:

The question for you, since you say you have had the lathe for several years - has the feed ever worked? If you never tried it, I'll suppose the lathe's apron has been apart and put back together without that key - before you ever got it

I'll suppose its even possible that this disabling was decreed by school management - to make it more difficult for the "children" to maim themselves

Click to expand...

Although I've had the lathe for a couple of years now, I only recently really concentrated on learning the controls and how to use it. I discovered, among a number of other minor details, that the saddle did not move so I could only move it with the hand dials. I thought I was using the controls wrong.

So I think your theory on keeping the kiddies from maming themselves pans out.

What's wrong with this picture?


There is no key in the worm gear! I checked eBay, with no luck yet. I will contact Grizzly tomorrow and see if this is one of the few parts they may still have.

I'm excited to get this part and use my lathe more effectively. I will say that with help here and too much time watching youtube videos, I have learned alot about my SBL 14.

Easy to make such things if you need to - and good practice - and a confidence builder

Glad the cause for "no worky" was easy to find