Sealing oil reservoirs in leaky cast iron

[machinist60]

I have a chinese lathe mill/drill. I cannot keep oil in the headstock. Seals are ok, it just leaks out on its own, I suspect the casting is porous underneath where it sits on the bed. Does anyone have a fix?

TIA, John.

[bob_s]

Try using the epoxy based gas tank sealant available at your local auto supply.

[Tinkerer]

Pull off the front plate... I'll bet you'll find your oil leak is in one of the shift lever seals. Mine had a mystery oil drip finely tracked it down... found a little tare in the 1-3 seal clean with alcohol and repaired in place with super glue.

[Nutter]

I have heard that Glyptal paint works well for sealing porous castings.

http://www.caswellplating.com/aids/glyptal.html

[Evan]

Butyrate aircraft dope from the hobby shop works well for sealing cast iron. It is impervious to petroleum based chemicals. That's why it's labeled "hot fuel proof" and is used on real aircraft.

[pcarpenter]

Evan-- is nitromethane considered "petroleum based"? It's hard to argue that its not hydrocarbon based, but I didn't knwo it was petroleum based per-se. The presence of Nitromethane is what made model airplane fuel "hot" as compared to pure alcohol based fuels...or going back even further....gasoline or diesel fuel.

Glyptal as already mentioned is what is used inside engine castings and others. I would think it would be hard to get any gearcase clean enough to apply this sort of thing without complete disassembly and lots of hot soapy water or other cleaners.

I would suggest some other investigation first. My Chicom lathe had a persistent leak that I was sure was related to either porosity or a seal. It was very hard to tell as the headstock casting bolted tightly to the QC gearbox casting and both were oil bath. As it turns out, I solved my problem with a tip from someone else here. Oil is slung constantly against the top cover of the headstock gearbox. I removed the gasket and cleaned both surfaces. I waxed the top of the casting and applied RTV Silicone sealant to the lid and assembled by hand with no screws. When cured, I pulled it back apart and cleaned off the wax and trimmed the excess silicone. This created a silicone gasket that is permanently attached to the top cover.

What had been happening was that oil leaked out from under the top cover and wicked down behind a "label" plate on the front....making it look like the leak was in the casting somewhere I could not see...or perhaps from a seal.

I also added a brass pipe plug to the top cover with vent holes I added around the periphery of the brass fitting. This prevents changes in temperature from creating internal pressures and forcing oil past seals.

Paul

[Evan]

Nitromethane will eat nitrate dope but not butyrate dope. As for nitromethane being petroleum based, with the processes available today virtually any feedstock that has the right elements in it can be synthesized into whatever you wish that contains those elements.

Nitromethane is an organic solvent. Organic in this case doesn't mean grown without pesticides or even related to life forms. It means it contains carbon and hydrogen which are the two elements in hydrocarbon petroleum products, which are also organic compounds. Nitromethane also contains nitrogen and oxygen so it isn't a hydrocarbon.

[machinist60]

Thanks to all who replied, John.