South Bend 9" JR Rebuild Question

DECOMGuy · Jan 6, 2011

I've finally gotten serious trying to clean/rebuild a 1928 South Bend 9" Junior lathe and I am scratching my head trying to figure out why the apron gearing alignment is, well, not in alignment. I appears that the aprom gear shaft is either bent from a handling misshap (not on my watch!) but perhaps is was designed this way as an eccentric to accomodate casting issues. Here's a photo of the part in question: Pictures by dmdawson - Photobucket

If anyone can confirm it should be straight (or not) I'd appreciate it. BTW, I will soon be posting more pics of the lathe now that I've figured out how to do it.

Dan

kitno455 · Jan 6, 2011

Trust your gut. It's bent ;( Probably got dropped on it's face at some point.

allan

MetalMunger · Jan 6, 2011

Not bent! The neutral axis is merely challenged

phantom71 · Jan 6, 2011

Definitely bent, I also have a 1928 9" jr. Does yours have the overhead drive as well?
The same shaft was bent on my 10" logan when I got it, my boss was able to heat it and straighten it good as new, if you have no luck fixing it or finding another from other members or fleabay get back with me, I may have an extra. I haven't been feeling well of late so it may take me a couple days to make it out to the shop and check.
Cheers'
Mitch

DECOMGuy · Jan 6, 2011

Thanks for the information. I'll take a bunch of pictures over the next day or so and post them. Mine has the overhead drive. The spindle is in good shape (as far as I can tell) but the drive shaft bushings (on the overhead drive) are in sad shape. I guess I'll try to see if I can straighten it out and see how that goes. I hope you get to feeling better.

gkemper · Jan 6, 2011

I vote for bent.

Dennis Turk · Jan 6, 2011

I think to date I have replaced five or six of these bent gear pins. These have not only been on the tool room lathe but also the Jr. models. On the tool room lathes it looked like the results of a crash wile power feeding but on the Jr. that cant happen. My only idea was there must have been a gorilla on the hand wheel trying to take a monster cut.

Turk

sledzil · Jan 6, 2011

DECOMGuy said:
the drive shaft bushings (on the overhead drive) are in sad shape. I guess I'll try to see if I can straighten it out and see how that goes. I hope you get to feeling better.

I have the exact same lathe, the 1928 9" Jr with the overhead drive unit and the used to be silent drive. I converted the silent drive to belt drive, using an idler to force the ax drive belt to get a full 1/2 wrap around the 1 3/4 pully on the motor. The babbit bearings on mine are a little loose, but seem ok. I think if they were to be repaired, I would see if I could bore out the babbit and insert bearings or oilite bushings. I also installed an automotive serpintine belt without splicing. When I run just the spindle, the only noise I hear is the hum of the motor....

If you need felt for the spindle, I have some. I managed to get a gallon of spindle oil and a gallon of ways oil from enco for about $50.

1955-view-showing-installed-serpentine-belt-without-splicing.jpg

Dennis Turk · Jan 6, 2011

When SB switched from the chain to the belt they used the two step pulley that was used on the workshop lathe as well as later on the heavy ten and also on the early heavy 9 under drive lathes. You will see a cross bar that is cast between the two extensions of the top plate that the motor is mounted to. This little cross brace was used to support the front of the chain guard on some models. When SB went to the large two step flat pulley they cut this little cross brace out for pulley clearance. SB also used the normal two step motor pulley that is larger than the one your using. I have a 11 inch as well as a 9 inch with this setup.

Turk

sledzil · Jan 7, 2011

Dennis Turk said:
You will see a cross bar that is cast between the two extensions of the top plate that the motor is mounted to. This little cross brace was used to support the front of the chain guard on some models. When SB went to the large two step flat pulley they cut this little cross brace out for pulley clearance.
Turk

Thats how I put in the belt. I cut out a 3/8 slice from the cross brace, then milled a filler section from aluminum that bolts into place from the rear of the brace. If you look at my picture, you can see a slightly lighter gray band just to the left of the belt on the top plate. I thought I was messing with something I shouldn't have, and I guess mother SB seemed fit to remove it later.

DECOMGuy · Jan 7, 2011

I've posted some "before and after" pics at: Pictures by dmdawson - Photobucket

So far other than rust removal and painting (appologies for the non-standard color choice) the only mechanical thing I've done is to fabricate some legs and add an automotive serpintine belt without splicing.

Dennis Turk · Jan 7, 2011

Just a thought here. With the use of the smaller pulleys then what SB did and the addition of the idler I think you are putting more load on the babbit bearings the counter shaft runs in. One feature of the large pulleys and especially the flat non V grooved pulley on the counter shaft they exert less load or force on the bearings. With the greater area in contact with the belt (5L size) you would have just as much torque transmission from motor to counter shaft. Mite not be much but there would be some reduction in the bearing load.

Turk

sledzil · Jan 10, 2011

Dennis Turk said:
Just a thought here. With the use of the smaller pulleys then what SB did and the addition of the idler I think you are putting more load on the babbit bearings the counter shaft runs in. Turk

I agree. However, using an idler to wrap the belt around the motor pulley allowed me to use a very light belt tension. I'm using a 1.75" motor pully and a 6" cone pully for about 825 rpm max.

Dennis Turk · Jan 10, 2011

sledzil said:
I agree. However, using an idler to wrap the belt around the motor pulley allowed me to use a very light belt tension. I'm using a 1.75" motor pully and a 6" cone pully for about 825 rpm max.

Remember these old girls spindle speed was only 480 rpm or close to that. The one of mine you see on Tony's site I know runs under 500. I would not want to run one of these old plain bearing soft spindle SB's much over 800. Even then I would think you would run into some vibration problems in the head stock. Given a counter shaft speed of 825 when your on the high speed setting on the spindle pulley I would think that you would be over speeding the spindle. I know a friend of mine tried to speed his Dads old 11 inch up and when it went over 800 the lathe tried to run out of the shop. With the introduction of the capillary oil feed system to the spindle bearings SB was able to speed the spindles up but on these old total loss oiling systems you run a very big danger of seizing up or galling the spindle. If you run it very fast watch the heat build up in the bearings.

Turk

sledzil · Jan 10, 2011

Dennis Turk said:
Remember these old girls spindle speed was only 480 rpm or close to that.
Turk

Something tells me my memory of what my rpm meter said might be faulty. I did find that the problem DECOMGuy has is also affected my lathe. I thought things were worn and had started shimming the rack. I decided to get the half nuts repaired and upon disassembly, found my apron gear shaft is also bent...Grrrrr.

Dennis Turk · Jan 10, 2011

I have made several of these apron bed feed gear shafts from pre heat treated
17-4 Ph Stainless but a pre heat treated 4140 should be about the same. Good stuff both of them. The shaft in your apron was not leaded stock like so much many others in a SB lathe so I figured SB knew they had a problem area. Fact its a problem with all single wall aprons. SB kept using them a lot longer than other mfg's did.

Turk

DECOMGuy · Jan 11, 2011

I chucked the apron gear shaft in my lathe; started turning it slowly; applied a oxy/acetylene flame until the base was plastic; slowly "re-aligned" the bent shaft and brought the tail stock up w/ a dead center until the shaft ran true. I'm sure I screwed the hardness of the steel but the shaft is performing well now and the whole operation took less than 20 minutes. I still can't figure out how the shaft got bent given the integrity of the apron and bed were not compromised.

bbass408 · Jul 26, 2012

Is heating and bending the only way to straighten these bent apron gear shafts?

My lathe clearly fell over (at least) and that shaft is bent w/ noticeable wobble in the crank wheel. It's also a little loose (up and down only) in it's hole in the apron. I'm curious how I'd even get it out of there? I don't want to heat it while it's on there. And, if I try to bend it while it's in there cold (if I even could) I'm worried I'd break something. I'm thinking I might have to dremel saw it out of there.

jayhawkman · Jul 26, 2012

If any 9" junior owners need their half nuts rebuilt I can help them out there. I have pics of the ones I did for my lathe but havent been able to get them to load up here on PM.

Mgrder1 · Jan 20, 2015

I know this is an old thread but has anyone else ran into this bent shaft problem lately? I tried to straighten mine cold by putting in a 3/4" collet in the mill and using the side of the vise to bend it back but it just springs right back. I think heating it is the only option at this point. When I took the apron off I could see where someone had brazed the top half-nut back together so it's my guess that someone at some point crashed it. Who ever fixed the half nut did a pretty good job so I think I'll let it ride and not replace it...what do you guys think? I don't see any wear on the lead screw that suggests the top half nut is riding unevenly.

South Bend 9" JR Rebuild Question

Plastic

Titanium

Aluminum

Hot Rolled

Plastic

Aluminum

Stainless

Plastic

Stainless

Plastic

Plastic

Stainless

Plastic

Stainless

Plastic

Stainless

Plastic

Plastic

Stainless

Aluminum

Similar threads