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  1. #1
    Join Date
    Oct 2019
    Location
    NSW
    Posts
    20

    Default New Hercus Model C's Owner

    Hey Guys,

    Have just in the last week joined the Hercus gang. I purchased two model C's in a package deal with a horizontal bandsaw as well (old Hafco BS-4A).

    One is standard with a 240v motor and pulley assembly (serial number 11832, light green colour in pictures), with the original tail stock and a thread pitch gauge.

    The other has a 3 phase motor and VFD (serial number 2628), the seller had the motor wired in star not delta so wasn't working correctly; this lathe had a tail stock but it is not the original to this lathe.

    They came with two of the standard English 3 jaws chucks but one is missing 1 jaw, as well as an import Sanou 4 jaw chuck. The Sanou doesn't fit the backing plate so will have to turn down the shoulder on backing plate to allow it to be mounted.
    Both have turret style tools posts as well as coming with an extra lantern style. The were 2 drill chucks and lot of HSS cutters and bits and pieces.

    Unfortunately they didn't come with any additional gears, steady rests, live centres, etc.

    Thinking I will play around with both for a bit before deciding on which one to completely pull apart and restore first, seems ideal to be able to do this and have one lathe not in pieces.

    The guy I bought them off had an interesting idea regarding screw cutting on the 2nd lathe with VFD.
    To put a tachometer on the spindle and then attach some kind of motor and VFD to the lead screw. Then if I knew the relative speeds required between the 2 for different thread pitches I could perform screw cutting without needing gears. Does this sound possible? I have a washing machine motor I have been saving for something such as this. I know working out the relative speeds could be difficult.

    Also I have no prior metal turning experience, so will be learning lots on these machines!

    Thanks,
    Tom
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  2. #2
    Join Date
    Aug 2015
    Location
    Adelaide
    Posts
    239

    Default

    Hi Tom and welcome to the Hercus club.

    In relation to the theory of running a second motor on the leadscrew with tacho's on each part I would say don't even bother trying to do it, you would have to be so exact that a few rpm would throw the thread off pitch and the motors would need to start and stop at exactly the same time and ramp up and down to speed at exactly the same time so you can keep the relationship between the spindle and the thread, change gears are so much easier to deal with and everything is going to remain at a constant whilst they are engaged to the leadscrew.

    Hopefully you get great enjoyment out of restoring the lathes and yes you are much better with having a second one running for polishing partss and making little bits and pieces that you will probably need.

  3. #3
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,183

    Default

    Welcome Tom. I like the bright green! (though hardly an original colour)



    I also thought of the direct-drive lead screw idea. I suspect a lot of people have. Don't know if anyone has done it.


    1. I'm not sure a tachometer on the main spindle would be enough. A rotary encoder, so you get hundreds of pulses for each revolution, means the threads could actually be accurate. It also means you could turn the chuck/spindle slowly - even by hand!
    2. A heavy-duty stepper motor might be more useful than your average 2 or 3 phase with a VFD. That way, you could exactly match pulses in vs pulses out, and you can get a much wider range of RPM without gears and pulleys from motor to lead screw.



    On an imperial Hercus, the lead screw is 8 tpi, so 8 rotations moves your carriage and cutter by one inch.
    • If you were turning a 24tpi thread, it would have to turn at 1/3 of the spindle speed.
    • If you needed to do a big 8tpi thread (like inside a new faceplate to mount your little Sanou 4jaw onto the spindle), it would have to exactly match the spindle rotation

  4. #4
    Join Date
    Nov 2018
    Location
    Tasmania
    Posts
    97

    Default

    In regards to the motor driven leadscrew, I would recommend watching Clough42's electric leadscrew series on youtube, he is able to cut metric and imperial with the kit he's got

    The alternative is to make gears (actually not to difficult if you have a mill and dividing head)
    Or go a step further and make a quick change gearbox like I stupidly did (a lot of work, I would not recommend)

  5. #5
    Join Date
    Oct 2019
    Location
    NSW
    Posts
    20

    Default

    Thanks for the responses guys, took so long to actuality post since I tried to post that I haven't been checking this forum.

    Well luckily I got a great deal on nearly all the gears I need from a guy off gumtree, so will be able to start playing around with some thread cutting.
    It has been really fun doing some basic turning. Its interesting that metal lathes much such a different kind of mess to a wood lathe. Not as persistent but still a lot. What are peoples technique for cleaning up the metal chips? I have been using a brush and some macca's trays.

  6. #6
    Join Date
    Jul 2012
    Location
    Griffith NSW
    Posts
    435

    Default

    While ever you cut a thread thats not a direct copy of the leadscrew (8tpi), then you are going to create a situation where the spindle and the leadscrew are not at the same point in their rotation at all times. Cutting any non-8tpi thread means you have to wait until the two rotating elements are at the correct, common point in their rotation before you can engage the thread cutting process. This means that if you want to use an electronic leadscrew, you need to have accurate measures of both the speed and rotational location of both spindle and leadscrew.

    Its doable, Ive read about a guy making his own for a home shop. Its a massive job though.

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