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Schaublin 135 rebuilding project- ongoing thread

Another topic I wanted to ask for your advice- the internal compartment of the apron, the gearbox and the headstock are originally painted. I’m not sure why they decided to paint them. I thought about rust control but these areas are always full with oil. Anyway, inside the apron and the gearbox the paint started to swell and to come off. I’m hesitating to leave it as is, to remove the paint with paint remover (w/o complete disassembly of all parts) or to make complete disassembly, clean and repaint. I assume repainting will be challenging, as all oil must be removed completely from these internal cavities and special paint must be used (similar to what they use for oil containments). This will probably require soaking / sand blasting. What do you think?
 

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The reasons for painting the inside of cavities in cast iron components is 1. To prevent dust and casting sand from coming loose, 2.To make the surface smoother and easier to clean out (when changing oil etc). The problem is that the paints used often dissolve in the oil over the years, and acts opposite to what is intended. I have used 2-pack polyurethane machine paint for the in- and outside of my machines, as this is both quite oil resistant and adheres extremely well, like glue. First you need to get out as much as possible of the old paint with mechanical and/or chemical means. I have used Finnish Tikkurilla Temadur 50 (the number is the gloss in %). Another supplier is Friedrich Pietzcker ltd. in Hamburg, I have used their Strukturlack PU, it is a highly tixotropic ("thick") paint that may be used to achieve a rough structured surface both by spraying and rolling. This paint is probably not available in your area, i have bought it directly at the factory (yes, I drove by).
 
Ole thanks for the elaborated info. Various industrial paints for harsh environemnt and chemical resistancy are available here, both from local production and imported. Specifcially PU paints are easily available. There are two hurdles which come to mind:
1. Full disassembly of the gearbox and the apron are a long projects on their own and there is always a chance of damaging something.
2. These paints will fail prematurely if the oil is not completely removed in the sense that even microscopic oil film should not remain on the metal. This is usually not easy to obtain w/o sandblasting. How do you usually remove any oil residue?

If I must go there, then I must go there...

Aviv.
 
If you have an engine rebuilder facility around, they usually have boiling vats to clean engine blocks and such. This will work very well to clean your castings of everything, paint, oil etc. Of course you'll need to strip down the components to nothing. I don't know if this would be available there, but two part tub and sink epoxy worked quite well for me, and is still hard immersed in oil over 20 yrs.
 
Daryl is right, epoxy also works fine. Regarding getting rid of all oil, filler and old paint: Hardly ever realistic with a complete lathe. Clean as well as you reasonably can. Scrape off all loose flaking paint. Clean with solvent, rags and brushes. In your case; Is the white paint someone put on, possible to remove completely with thinner or similar? If you plan to use filler, decide on type, and prime with a compatible primer. Fill, and sand everything wet with 250 paper. Roll or spray 3 topcoats. Do not use a gloss topcoat, max. 60% shine - this is not a car. The reflective surface will reveal every little blemish, and you might be afraid to ever use the machine for real work!
 
Today I completed the disassembly of the apron inner parts, as well as most of the gearbox. Both contain many small parts and bearing balls that can easily get lost. I hope my documentation is good enough so I can later assemble all the gears and the selectors in sync. If anyone can identify synchronization insteuctions in the manual/diagram, please let me onow ao I can check myself against. Here are some photos. I have more, if anyone needs- PM me.
 

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And the gearbox. The upper parts (e.g. the top selector mechamism) show signs of lubricant starvation, suggesting that oil splashing to the upper part of the gearbox is not very good.
 

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And more.
 

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Now I’m bit stuck with the KM5 lock nut that can be seen in the first photo of post #68. Access is quite chellenging as obviously socket cannot be used. I assume they had some soecial tool for this purpose. I tried to punch it but it didn’t work. Any ideas are welcome.
 
A 'tool' is going to be needed, not sure there are any off the shelf ones but maybe a hand made one made with some steel plate, an angle grinder and a welder.

Impressed with the work you are doing, its a huge job but having empty castings and the knowledge that as you get to start re-assembling you can check every part and ensure its going to be great for the next 50 years!
 
1711265097596.png

You might be able to find something like this, a 'castle nut wrench' and modify it to suit your access and size needs, there are also nut versions of this tool again which might be a starting point to make a tool to suit.

Good luck.
 
Thanks Marc. I saw OTS spanner and socket are available, none of them can be used (the nut is buried below the surface). Something like an open socket holded from the side should be used. I guess I’ll have to make something like this.
I’m thinking to take a std socket of approx. the right size, than machine the castle, then cut it open. Starting something like this:
 
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Another advice needed- in the course of the apron diassembly I lost few bearing balls which were located inside of the dog clutch. The manual says there should be 60 balls of 3.5mm diameter, but actual measurement of the balls shows 3.47mm diameter. The only source I could find for 3.47mm bearing balls is Aliexpress, with no precision rating or anything beyond "precision balls". Any ideas from where I could source few balls from a respected sources?
 

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I would suggest that you buy 60 new balls of 3,5mm and try to fit them, and replace them with 3,47mm from Aliexpress if they're too tight.
 
Interesting approach. I would assume it has some reason why the used (or moved to) 3.47 but I could try. Which grade you would use?
 
The project continues with sanding, wire brushing and preparation for painting. It seems that originally the external surfaces were covered with body filler, then painted. Internal areas are brushed with base coat only. The original paint and the body filler are stable and in a good shape. I saw no reason to remove them completely. Rusted areas that were hit were sanded down to bare metal. I decided to use rust converter in order to treat rusted areas where it’s impossible to remove the rust completely w/o sand blasting. Either hard to reach areas or highly pitted areas. I have had good experience with rust converters over the years. If used correctly, they transform rusted areas into black stable surfaces and are very easy to work with. Tomorrow I will fill visible dents and continue with a base coat.
 

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Any ideas how to clean and brighten exposed accurate surfaces like the ways w/o damaging them?
 
And with the base coat…
Is it perfect- not at all. Is it good enough for me?! yes. I’m too old to seek for perfection.
 

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