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Sebastian Lathe info

I pulled the gearbox cover off and the gears are tight, in good shape and shift fine. The guy at DC Morrison said use 30 wt oil, but it has 90 wt gear oil in it. It is supposed to have an oil level standpipe indicator attached to the plug but it only has the plug. Debating how much oil to add when replacing and whether to replace with 90 wt. 30 wt non detergent is hard to come by. I don’t see a downside to detergent oil except it cleans old seals out and they stsrt leaking sometimes. Might just fill it up to the level of the 1st shaft so it is not standing at seal level.
 
An alternative to 30 wt. non-detergent is good old ISO 68 hydraulic oil. Even ISO 46 will work, too. Really any oil is better than none at all. The current gear oil is not a show stopper, but if you can replace it with something lighter. It's the bushings that may sleigh up using the heavier oil.

Edit: If any of the seals are leaking, which I doubt there are any, add a bottle of seal conditioner from any auto house. It'll stop the leaks. That's what I did to the headstock on my 14" Rockwell lathe a few years back.
 
30 wt non detergent is hard to come by. I don’t see a downside to detergent oil except it cleans old seals out and they stsrt leaking sometimes.

Autozone stocks 30 wt non detergent.

I think the oil seal leaking issue is more from synthetic oil, not necessarily detergent oil.

The purpose of the detergent is to suspend dirt particles to allow them to flow through a filter.

Without a filter to trap the dirt, the dirt will flow repeatedly through the system.

Non-detergent allows the dirt to eventually settle and become sludge in the bottom of the case, like the old days.

Mike
 
Bigger question is how much to fill it. Will measure what I drain out but it is barely above the plug. Standpipe is gone. Gears on lower shaft seem to splash up on everything else.
 
The chuck with this lathe is original to the lathe I think. Missing a chuck key. I tried a 1/2 inch ratchet. Not 1/2 square, not 3/8. Is there a standard for SAE tooled lathe chucks? Maybe 7/16?
 
The chuck with this lathe is original to the lathe I think. Missing a chuck key. I tried a 1/2 inch ratchet. Not 1/2 square, not 3/8. Is there a standard for SAE tooled lathe chucks? Maybe 7/16?
Nope! They all use something different. I've made several chuck keys over the years for some of the chucks I have. Haven't once got one that was a perfect fit other than the one's that came with a chuck.
Ken
 
Only needs one gallon of oil. I used 30w compressor oil from AutoZone. It's a non-detergent oil. Just enough for a few gears to dip into it. Any more than that, and it will leak out the spindle nose's "labyrinth seal" which doesn't have any rubber components to actually seal. Just a lot of baffles meant to catch splashed oil and redirect it back inside.
 








 
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