New oil for old lathe
I have a Clausing 5914, which also has the variable-speed system, which is hydraulically controlled, and caused me a heap of trouble till figured out that I was not using the correct viscosity of Mobile DTE hydraulic fluid. I wrote a saga on the issue, which follows:
This saga started in 2009, when I was attempting to get the variable-speed drive on my new old Clausing 5914 Lathe to work properly. The mechanical repairs went well enough, but I was never able to properly purge the air from the hydraulic system. At the time, I noticed that whenever I performed the recommended maneuver of pushing the speed control lever past the lowest speed to uncover the purge port, I could hear the upper hydraulic assembly (131-015 Cylinder) aspirating air, so I was just chasing my tail.
It seemed to me at the time that the Mobil DTE24 hydraulic oil I was using was too thin for the purpose, but DTE24 was what Clausing recommended to replace the original and now obsolete Shell Tellus 27 oil (used in the hydraulic system and the headstock) and DTE25 to replace Tellus 33 (used in the apron gearbox).
I considered adding an external reservoir to the hydraulic assembly so the distance from port to the free surface of the oil would be long enough that aspiration would be impossible, but never did anything about it. My 5914 has the new rectangular aluminum hydraulic assembly with built-in reservoir, not the older cylindrical steel hydraulic assembly (which has an external reservoir and was my inspiration for adding an external reservoir).
The story is documented in the <rec.crafts.metalworking> thread "Rebuild Clausing 5914 VS Control Hydraulics" in June 2009:
Rebuild Clausing 5914 VS Control Hydraulics - DIYbanter
I returned to the problem in April 2015, intending to add that external reservoir, and so was looking to buy a spare rectangular aluminum assembly. This led to the usual questions about what I intended to do, which elicited a number of useful suggestions from the <
[email protected]> list. The thread is titled "Upper VS hydraulic assembly of a 5900-series Clausing lathe sought".
One of the responders to my questions provided the key clue, that the oil industry had converted to ISO oil viscosity grades, replacing a confusion of names, and Shell had therefore renumbered their Tellus oils.
My 5914 was (if memory serves) built in 1975, and the manual is dated December 1969, which is well before the transition to ISO Viscosity Grades began, so Tellus 27 and 33 were the pre-ISO designations.
Now, the new and old Tellus product designations look the same, and it appears that people assumed that Tellus 27 was closest to Tellus 32 and Tellus 33 was closest to Tellus 37, based on the product numbers alone, but it just isn't so -- the units of measure had changed. It's like confusing yards and meters.
We had in 2009 realized that there was a conflict, but ultimately assumed that Clausing was correct because they were the manufacturer. But they were *not* correct, having fallen into the interpolation trap as well.
The clue mentioned above is a substitution chart from the transition era:
Shell Oil Cross Reference | Liquids | Oils. This chart gave the equivalents of Tellus 27 and 33 as Tellus 46 and 68 respectively, these being named after their ISO Viscosity Grades 46 and 68. These are an entire viscosity grade thicker than the original substitution recommendation from Clausing. DTE24 is ISO 32.
Did later manual Clausing machine tools with VS drives call out the correct oil?
Some people use automotive Automatic Transmission Fluid (ATF) in the hydraulic system, and have no problems. It turns out that at room temperature (20 C, the temperature of the hydraulics in a 5914), the viscosity of ATF III is almost identical to that of ISO 46 hydraulic oil, which explains why ATF III worked.
So, the bottom line is that one should use a good grade of ISO46 hydraulic oil in the hydraulics and the headstock, and ISO68 in the apron gearbox. This would be Mobil DTE25 and DTE26, Shell Tellus 46 and 68, and so on. Hydraulic oils are commodities, and these are all good.
I then purchased the thicker grades of hydraulic oil and installed them in the 5914 lathe, an easy but messy job. The effect was dramatic:
Variable-Speed Hydraulic Control System: It's like night and day. I was for the first time ever able to purge all the air out of the hydraulics in one or two cycles, versus the usual ten or fifteen cycles mentioned in various instruction sets. (I always wondered why Clausing would build a lathe to require any such thing. Now I know what happened.) There was no tendency to aspirate air while bleeding. The VS system now works correctly. DTE25 (ISO VS 46)
This also explained why sometimes the purge process worked and sometimes it didn't -- ambient temperature was the reason. In cold weather, the oil thickened and aspiration was tolerable. In warm weather, the oil thinned, and aspiration was unavoidable.
Headstock: With the new, thicker oil, the lathe runs far quieter. This was a welcome surprise. DTE25 (ISO VS 46)
Apron: No obvious difference. But one should change the apron oil from time to time. DTE26 (ISO VS 68)
The old oil in headstock and apron was a shade or two darker brown than the new oil, but was otherwise in reasonably good condition. Aside from the air aspiration problems and the noise from the headstock, the thinner oil was workable.
I purchased the oil from McMaster-Carr, who charged me $26 per gallon. MSC wanted $37 per gallon, so it pays to shop around.
Joe Gwinn
20 April 2015
) someone would be able to help.
