- Joined
- Jan 21, 2011
- Messages
- 88
I thought I would post this simple fix as I'm sure I am not the only one that has this problem.
When my Craftex 12" x 36" lathe was around a year old the two bottom shifter knobs on the feed transmission started leaking oil.
Both lower shift knobs are below the oil level and would leak about a tea spoon of oil every 24 hours.
I kept a plastic tray under the transmission to catch the leaking oil.
Adding oil requires the cover over the transmission drive gears on the end of the lathe be removed to access the transmission fill plug.
A bit of a nuisance, I have been filling it with grade 46 hydraulic oil.
The shifter knob shafts have a pinion cut on the end and turning them moves a rack back and forth sliding
gears into and out of engagement. There are O ring grooves in the shafts that seal them.
I suspect that the machined surfaces for the original O rings were left rough and the O rings wore away as a result.
Removing the cover with the leaking shaft seals would not be a big task but getting it back together might be a pain
if one of the racks moves out of place. I thought there has to be a simpler way.
The shifter knob has a large key-way cut in it so so cutting an O ring groove in it is not an option.
I decided to cut a groove in the back of the leaking knobs and make an insert with an O ring that seals
the shaft to the face of the transmission housing. I used an O ring from a kit for hydraulic face seal type fittings.
They are a hard 90 durometer rubber. The O ring was a slight stretch fit on the shaft and the insert compresses
another .010" in diameter and compresses it approximately .010" against the transmission cover.
It's been a few weeks now and no more oil leak. If the new seals start to leak it's only a few minutes work to replace them.
Terry
You can see the leaking oil in this picture. The O ring and insert have to be put in place on the shaft and then the key and knob installed.
When my Craftex 12" x 36" lathe was around a year old the two bottom shifter knobs on the feed transmission started leaking oil.
Both lower shift knobs are below the oil level and would leak about a tea spoon of oil every 24 hours.
I kept a plastic tray under the transmission to catch the leaking oil.
Adding oil requires the cover over the transmission drive gears on the end of the lathe be removed to access the transmission fill plug.
A bit of a nuisance, I have been filling it with grade 46 hydraulic oil.
The shifter knob shafts have a pinion cut on the end and turning them moves a rack back and forth sliding
gears into and out of engagement. There are O ring grooves in the shafts that seal them.
I suspect that the machined surfaces for the original O rings were left rough and the O rings wore away as a result.
Removing the cover with the leaking shaft seals would not be a big task but getting it back together might be a pain
if one of the racks moves out of place. I thought there has to be a simpler way.
The shifter knob has a large key-way cut in it so so cutting an O ring groove in it is not an option.
I decided to cut a groove in the back of the leaking knobs and make an insert with an O ring that seals
the shaft to the face of the transmission housing. I used an O ring from a kit for hydraulic face seal type fittings.
They are a hard 90 durometer rubber. The O ring was a slight stretch fit on the shaft and the insert compresses
another .010" in diameter and compresses it approximately .010" against the transmission cover.
It's been a few weeks now and no more oil leak. If the new seals start to leak it's only a few minutes work to replace them.
Terry
You can see the leaking oil in this picture. The O ring and insert have to be put in place on the shaft and then the key and knob installed.
