Clausing 5914 variable speed wont slow down

Hello all, I've had my Clausing 5914 for a few months, learning as I go. The variable speed drive has worked fine the whole time, except not returning all the way down to slowest speed (500 versus 360). Althogh I think that's just an adjustment issue on the lower pulley.

But today it will barely slow down the spindle. Runs up fine, have to hold for a minute or more for it to return to slowest speed. I've ran it up and then held it down slow a few times to bleed it, with no change. When I turn the dial to increase speed it feels just fine, but when I try to decrease speed the dial feels like it's at minimum with no resistance. I can hold it there for a few minutes and get it to come down.

I feel like it's likely an internal seal, but wanted some input for those that really know them. I've searched with only the bleed procedure being advised. Appreciate the time!

That sounds like a classic air-in-the-hydraulics problem, requiring bleeding. There is also a groups.io forum for Clausing lathe and mill, with a lot of specific expertise and literature in files. I have gotten a fair amount of benefit from being a part of that group. I also have a 5914 with the notorious vari-speed drive...

I have a Clausing 1300, but they all seem to suffer from leaky seals. Mine leaks from somewhere down by the lower pulley and not enough to warrant disassembly.

Here is my procedure:

Top off the oil

With the spindle turning, run the spindle speed to its lowest setting and hold it against the stop for 30-seconds or so.

Typically I’ll get a couple big “burps” of air out.

Run the spindle to its highest speed setting and hold it against that stop for another 25-30 seconds.

Run the machine back to the slow end of the dial, hold it against the stop again.

Add oil again, if required

Start turning.

My machine sits idle a lot. Typically I’m adding a bit of oil every time I come back to the machine after it’s been sitting.

Lastly, Clausing suggests running the variable-speed through its entire range every day you use the machine.




Be safe.



Jeremy

If you look at the end of the upper cylinder, there is a small slotted round head machine screw in the wall that you remove to bleed the air out of the cylinder. Just holding the piston at the end of travel, won't remove the air- you have to take the bleed screw out.

Thanks all for the input.

Got back to looking at it, and it works fine now, after sitting for a week. And it will go down to 400 RPM (instead of 500. Still wont reach the 360 RPM point, but I'm betting you are right. I loosened the bleed screw with no bubbles, here's to hoping it continues!