Thread: Hardinge KL-1

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  1. #1
    Hello,
    I have fairly recently been lucky enough to get hold of a Hardinge KL-1 lathe, and though it would be good to share some of my experiences with it.

    I know the history of the machine for most of it's life as it came from the company at which I work, so most of what I plan to write about is, at least initially, about getting it to function.
    I hope this will also be a record for myself as well for what I did, so I apologise if some of the things I write about have already been covered!

    This is going in my garage, so no 3-phase there. It's the conversion to single phase - that's the first job.

    Here is the lathe:

    Click image for larger version. 

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    I'm not entirely sure of the manufacture date, as the serial number lists seem to be for US versions, not UK versions.

    Searching the various forums tells me:

    The main motor is a dual speed 0.5hp/1.5hp 415V_ac 3 phase motor.

    The speed change motor is a dual voltage (240V_ac/415V_ac) 1/20hp three phase motor.

    The coolant pump motor is also a dual voltage (240V_ac/415V_ac) three phase motor.

    The carriage feed motor is a 90V_dc motor.

    My initial aim is to power the dual speed main motor, really just to prove that the lathe is actually functioning, and there’s nothing seriously wrong with it.

    Paul.
    Last edited by pauly45; 10-09-2013 at 07:26 PM.

  2. #2
    I aim to power the lathe using three VFD's, and utilise the original controls of the lathe.

    The speed change and coolant pump motors can be converted to Delta 240V_ac operation.

    The main motor is something that I definitely want to use due to it's quality, and I've read that I need a step up 240V_ac to 415V_ac transformer and a 3-phase input VFD to run it.

    I the months waiting for the lathe to arrive, I gave up waiting for a transformer to appear on ebay, so decided to get a transformer manufacture to make me one.
    Last edited by pauly45; 10-09-2013 at 07:59 PM.

  3. #3
    Paul the money you are going to pump into stepping up for the 415v, you might as well just swap it out for something else. a good quality 3 phase motor that will work at 240v delta with a vfd would be far more logical. I had to do the same for mine and even put a lower hp in, a 2hp instead of the 3hp it replaced. Never regretted it at all.
    If the nagging gets really bad......Get a bigger shed:naughty:

  4. #4
    Would imagine a rotary converter would be the cheapest and easiest way.? Keeps every thing original plus neat and tidy.

  5. #5
    Trouble is they are not very efficient and take a bit of room. The OEM motor was meant for a purpose. A replacement motor would be for the new purpose. No problem changing a motor to do job it is meant for. A darn site lot cheaper as well unless you build? Most lathes are sold with different motors for the environment they are to be used in.
    If the nagging gets really bad......Get a bigger shed:naughty:

  6. #6
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 5 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,837. Received thanks 192 times, giving thanks to others 5 times.
    Rotary converter effiency depends on how well they're built.

    I built an ammeter into mine, and when sitting with no load the needle is barely above zero. The noise of the idler motor does annoy me, although that's probably more to do with it sitting on top of a bit plywood with minimal vibration damping!

    I am however considering upgrading to a digital convertor, as the latest purchase is going to be far too much hassle to convert to single phase, and may be pushing the power limits of the current rotary.

  7. #7
    I hear what you are saying about changing the motor, but the motor in the Hardinge lathe is a highly balanced motor, with two sets of windings for a low and high speed so there is just no sense in removing it and changing it for an inferior motor. Plus, the cost to convert using a transformer and VFD's isn't really that large.

    Yes, I may be going over the top with 3 VFD's, but this is a project and a challenge.
    I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive. It also makes sense to me as it retains all the original lathe controls.


    Some calculations for the transformer :

    The motor is 1.5hp which is 1.1kW (1hp = 0.746kW)
    Assuming a 90% efficiency of the VFD then 1.1kW/0.9 = 1.22kW required.
    Approximately, Transformer kVA = 1.22kW/0.7 = 1.74kVA.

    However, this rating would be for heavy, continuous operation, which I'm just not going to do, so I have gone for a 1.5kVA Autowound Transformer. This will keep costs and physical size of the transformer down to an acceptable level.
    An isolation transformer will be bigger and more expensive, and I've been told it's just not necessary.

    This will step me up from 240V to 415V, then this will connect into two of the connections of a 3 phase input VFD.
    I'll common up two of the inputs to share the loading on one AC cycle a bit more across the VFD rectifier diodes.
    Last edited by pauly45; 11-09-2013 at 01:28 PM.

  8. #8
    Quote Originally Posted by pauly45 View Post
    then this will connect into two of the connections of a 3 phase input VFD.
    I'll common up two of the inputs to share the loading on one AC cycle a bit more across the VFD rectifier diodes.
    I've never heard of this done before. Devices inside the drive use a particular phase for synchronisation, that's why they specify which terminal to use if you are on single phase input, also a 3phase rectifier relies on phases being 'out of phase' for the return current but 2 of yours would be 'in phase'.
    I hear what you are saying about the original motor but to be honest a modern 240v 3 phase motor is going to be just as good, the 240v drive will be cheaper and you won't need a transformer.

  9. #9
    "I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive. It also makes sense to me as it retains all the original lathe controls."

    Not sure if it's mine you saw but if so thanks! Mine's written up at

    HLV conversion to VFD - circuit and pics

    Six years on it's still working fine. If I were to do it again I'd probably somehow add an interlock to the speed change as various people suggested just to be on the safe side and also an external speed pot. But neither is likely to rise to the top of the projects list for a while.

  10. #10
    Quote Originally Posted by bikepete View Post
    "I've also seen another 'mycnc' contributors hardinge powered this way, and it's impressive.
    But nowhere did I see two of the VFD inputs commoned up as suggested, also LowEnergyParticle seemed to make most sense. Other than being 'romantic' about the old machine I don't see the logic (no pun intended) in not making use of it's digits inputs for control and preset speeds.

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