Problem SL-20 is leaking hydraulic oil from the drawbar.

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Thread: SL-20 is leaking hydraulic oil from the drawbar.

  1. #1
    Registered TXFred's Avatar
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    Aug 2009
    Austin, TX

    Default SL-20 is leaking hydraulic oil from the drawbar.

    Greetings all. I'll introduce myself first. My name is Fred and I'm a CNC programmer and machinist with about 6 months on the job.

    Our SL-20 has recently developed a hydraulic oil leak. Initially the leak was fairly slow, about one drop a minute, but it has been getting worse.

    I've attached a PDF file from Matsumoto that shows an exploded view of the cylinder. I'll use their part names to describe everything.

    The leak is coming from the back of the distributor case. There is an aluminum end plate that Haas uses in place of item 7. It's shown in this picture.

    SL-20 is leaking hydraulic oil from the drawbar.-2010-07-21-07-38-48-small

    This plate has an internal gutter that drains out of an overflow hole into the "mailbox" at the back of the spindle. That is where the oil is coming out.

    Initially, our "mailbox" wasn't properly sealed, so the oil was leaking directly onto the spindle motor fan. You can see in the above picture that I've had things apart and resealed all the silicone joints. This redirected the leak into the mailbox and into the coolant, but did not fix it. But at least the machine is no longer sitting in a puddle of hydraulic oil.

    In this next picture, I've highlighted the area where the oil is dripping. The oil doesn't show up well in the picture, but it's there. The overflow hole is behind the steel plate with the eight holes.

    SL-20 is leaking hydraulic oil from the drawbar.-inside-mailbox-jpg

    The connection between the distributor assembly and the rotating components on the spindle is seal-less. It relies on tight tolerances and a series of ridges to sling the oil into gutters and let it drain back out the bottom of the distributor case. What I cannot figure out is why it is no longer draining properly. Part of the problem is that there isn't an obvious drain path from the left side of the distributor, where the leak is, down to the distributor's drain. So I'm not sure how the excess oil is supposed to drain away.

    Some history on the machine. At some point in the past this machine was crashed, hard. I don't know details, but the distributor assembly got bound up against the rotating components and galled. It was removed and lapped smooth and then reassembled. I don't know if that's when the leak started. it was before I came to work here.

    I think that's all the info I have to give, but will gladly provide more notes and photos if needed. If you've read this far, thank you for your time. I welcome any and all suggestions.

    Fred Scott

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    Attached Thumbnails Attached Thumbnails SL-20 is leaking hydraulic oil from the drawbar.-inside-mailbox-jpg   SL-20 is leaking hydraulic oil from the drawbar.-cylinder-disassemble-procedure-pdf   SL-20 is leaking hydraulic oil from the drawbar.-2010-07-21-07-38-48-small  
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  2. #2
    Join Date
    Oct 2009


    It sounds like the crash that damaged the cylinder has been the start of your problems. As you've already said the cylinder relies on tight tolerences to work properly, I guess because it has been lapped smooth there is now room for the oil to leak through.
    Really I Only have two suggestions - one buy a new chuckking cylinder.
    or Two - if you could put up with having to top up the hydraulic oil every so often, then you could redirect the waste oil pipe into a container and empty it every so often. That way it will not contaminate your coolant.
    Sorry I could not have been any more helpful.

  3. #3
    Registered roundman's Avatar
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    Apr 2007

    Default Leak

    I have a sl 10 at work and a while back a drain tube clogged and coolant leaked into my hydrolic fluid. This will kill a pump and so the Haas man told us to fix the drain problem (clogged drain tube from back to interior of coolant tank inside the lathe). The Haas guy replaced a valve on my pump because it was not clamping with low pressure and when he did that my pump makes a big racket whenever I am over 140 lbs of pressure or so. The hydrolic oil is clean of coolant but this new noise is really annoying. Since the old valve did not have this effect I am hoping it is the new valve not the hydrolic oil pump going out. But watch out for hydrolic oil getting coolant mixed in.

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SL-20 is leaking hydraulic oil from the drawbar.
SL-20 is leaking hydraulic oil from the drawbar.