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StanF South Bend 9A Rebuild Thread

For the QC gearbox, I'd start taking measurement's for all the bushings, shafts, and gears you'd need to completely rebuild it, then put it back together with what you have. You can use the lathe to make some bushings and modify others off the shelf, and you might find with a little oil it's not bad enough to worry.

Locating the bores can be tricky since a cast iron gear box like this isn't your typical rectangular stock part, but it can be done. IMO it's worthwhile as 90% of the QC gearboxes are all worn out in the same fashion. Even if you get the bores +/- .005, it'll likely be better than where you start. Finding the bore locations takes a little trig, but otherwise can be broken down into an X-Y grid. I did a few holes in a Logan lathes QC gearbox years ago and found that I could see which sides of the bores were worn so I was able to indicate and bore the individual holes that way rather than trying to map out their dimensional locations. The wear rarely hits all the sides and typically just wears due to gravity dropping the shafts down, and/or the gears crawling up to one side under load.
QC Gearbox Shaft Slop:

Surprisingly, one end already has a bushing, so I'll look into replacing it. It measured oversized, so it'll take out some of the slop. There's also a few thousandths of shaft wear, but that will remain. Looks like McMaster has the Oilite bushings in many sizes, so I'm hoping that one will be a perfect fit.
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I'm still thinking about the other end, but will probably just live with it.
My QC had the same worn out bushing, and it had gone long enough to have worn out the shaft too. Was able to replace both which fixed 3/4's of the play in the gear box. They have an elaborate lubrication duct/tubing system built into the casting and I think it's important to make sure it's cleaned out and you have the felts in the proper places to meter the oil distribution, cause once it gets gummed up there's no way to oil the individual points. The two oil cups on top of the gearbox are linked together and lube most of the gearbox. I used a our solvent vat pump to flush mineral spirits through it using my fingers to cover the various holes and confirm solvent was getting all the way through the system.

IMO it's a good case study against detergent motor oils. I think a lot of guys grab it cause it's what they have and "any oil is better than no oil," but without the heat and filtrations system on an internal combustion engine, those detergents and other additives get gummy and start to build up in places. Just using the weight and type of oil SB recommends solves a lot of these issues. My lathe also had been used with water soluble flood collant which was a whole other can of worms. They can do it but I think you have to plan on regular disassembly for cleaning to keep the gunk out. Mist or spot coolant is better for machines like this.
The other problem with motor oil is it is designed to be hydrophilic to absorb moisture inside the crankcase when the engine is off. Running the engine heats up the oil and drives off the absorbed water. Years ago I had a '64 VW beetle that developed foamy oil, which is odd for an air cooled motor. Turns out I wasn't taking it out for long enough drives so the moisture was building up.
Nobody should be using any kind of coolant on a 9" SBL. Dab cutting oil with an acid brush as needed or squirt it out from a can IMO.
I recall cleaning out all of those oil passages in that casting. What a mess that was! I didn't have the luxury of a cleaning vat back then. Seem like I use a selection of drill bits and welding rods and a little Trichloroethane back then. Boy, I miss that stuff!
QC Gearbox Cleaning...

I removed the nameplate pins using the instructions here (Dremel, slot + well-fitting screwdriver).
(again, thanks to all the people who have posted all the info in the past - it is much appreciated!)
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All four came out cleanly...maybe I should go buy a lottery ticket tonight! 🤑

I also took off the lube chart tonight, and will paint under it. I popped these four out from the backside - they were sitting just proud enough to see them. As I mentioned earlier, I'm not going to try to re-paint this one - I just don't have the patience!
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I removed it because I bought an (alleged) original lube chart in nice shape off of eBay. It's just for cosmetics - the red part will pop on the new gray paint. I only care about originality to a point...so I'll probably just tap the holes for reinstallation. That way I can remove both the nameplate/lube chart in the future, if needed.
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Question of the Day!

The plug at the end of the oil gallery is hard metal, so I'm assuming it's some kind of tapered pin or just a straight plug. I can't imagine that it is threaded into place.

Any tips for removal? I'm thinking of centerpunch/drill/tap, then try to pry it out. Or maybe a slide hammer.

I may not need to remove it - I've already cleaned all the galleries with brake cleaner with the flex straw on the tip. It worked pretty well. I did use an entire can of it!
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Sounds like you got the oil passages cleaned out sufficiently. I wouldn't mess with removing that plug unless you just want something to do. Trying to remove it may open up a can of worms. That plug is probably only about 1/8" in length.
New pulley arrived and installed. Also a new belt.
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The plug came out very easily:
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I set up a little fixture with a 3/4" bolt to drill the bushing. I bought 2 extras, just in case.
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New on left...old on right
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I used the bolt as an arbor to drive it home.
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I drilled and tapped for a new 5/18-18 plug.
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I started reassembly between paint coats 1 and 2 because I didn't want to scratch the final paint during assembly. All new felts were installed. The first shaft went together pretty easily.

The gears look dirty in the picture for some reason, but they were all completely cleaned. The new bushing took care of a lot of slop, so that was worthwhile.
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2nd shaft was also pretty easy. (the "B" next to the tapered pin was for "Bigger Hole")
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Then a 2nd coat of paint:
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I also cleaned up the levers.

Question of the Day!
How are these lubricated? I assume it's just a sleeve bearing in there? (this is a 1945 War Production model)
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and painted...first coat:
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And the lead screw end bracket was also cleaned and painted:
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The damn leadscrew is no fun to clean:
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Not shown...the lever gate bracket and two screws were cold blued.

Also not shown...I received the new brass threading chart/nameplate. I'll get a picture of it installed (hopefully) tomorrow.


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Fewer parts for the QC gear box means progress is being made. Not shown, but the leadscrew is fully clean.
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Some cold blued parts, and new nameplate:
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As the QC Gearbox gets close to completion, I'm moving over to the carriage/apron. This was dirty, but in great shape:
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The retaining screw was cold blued:
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I should make some more progress tomorrow, as I'm staying home from work. We're expecting bad traffic because of the eclipse. The last weather forecast that I saw called for clouds, so it might be disappointing.
Stan, for lubrication of the tumblers, I use 20w Non detergent, just like the rest of the gearbox. Progressing very nicely.
Well cleaning the lead screw is pretty easy if you can rotate it slowly and using something powered. Your done now, but after your lathe is fully assembled and the screw starts to get loaded up with crap, find a roll of some thick string that will fit down into the thread flanks, soak it in whatever oil you want to use. You want the string diameter to be about what the widest part of your screw thread is. Get the screw rotating and pull the string into the screw threads, as it fills up with all the junk, then slide it to the next clean area of that string. It's soft enough to help it conform to the ACME threads profile with a bit of tension on each end. Just be careful to use a long enough length and hold it so you can instantly let go if it happens to start wrapping around the screw for any reason. I stole the idea from an old machinist book, but can't remember which one now.

Or I just use some electrical contact cleaner, it will instantly flush and blow off all the old oil and debris as long as the screw thread has already been cleaned at some point. Either method will work.

I didn't realize you are in the San Antionio area. I'm south east of you. Yeah, we won't be able to see any of the eclipse here either, not even a partial.
In case you live under a rock...there was a full solar eclipse today. It was pretty cloudy here, but I was still able to see enough of it:
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Path of Totality! :cheers:
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More interesting...the QC Gearbox got assembled:
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And installed!
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The gear train also got finished. I borrowed a good gear from this 10k lever:
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Gear train installed:
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One door closes...
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...and another door opens...sigh :(
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I already finished two easy parts:
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First, I made a tool:
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Then I added another upgrade item to my list:
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Then I added a (minor) missing part to my list:
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The compound came apart pretty easily:
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The cross slide was a little more tricky...there's no spanner hole on my lead screw bushing:
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Cleaning went pretty well:
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You may notice that the compound is rounded off a bit. My compound had deep gouges in it. Likely from hitting the chuck. So I ground the gouges out and ended up with this:
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Unfortunately, sometimes cleaning reveals things you don't want to see...another part added to the list!
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