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  1. #1
    Join Date
    Jan 2009
    Location
    Captains Flat
    Age
    71
    Posts
    122

    Default Parting off on Hercus

    Dear All

    How have experienced Hercus users mastered the challenge of parting off? I am aware of (but have not experienced) the frightening dig in risk of parting off. I am aware that Myford reduces this risk by rear (upside down) parting off tool post. I am also aware that goosneck parting off tool reduces dig in risk via its inbuilt "spring". I could part off by running lathe in reverse and upside down the parting off tool except when work held in chuck as this would unscrew my chuck (thread mounted not camlock).

    So, any useful tips appreciated.

    David

  2. #2
    Join Date
    Nov 2007
    Location
    Mt Crosby, Brisbane
    Posts
    177

    Default

    Parting tools dig in either because there is enough flex in the system for the job to ride up or the tool height wasn't set right at the start. Jobs in the hercus tend to be smaller and thus more flexible, the machine is generally less stiff, and operators tend to be less experienced and thus don't set up properly.

    I'm a big fan of a big stiff parting tool (note I specifically inserted the word parting to put you children off ) but if you bother to get your grind right, height and angle right, everything is nice and tight, and make sure your as close to your chuck as possible it'll go smoothly.

    Parting is just a high load job so you have to be more precise with setup. Cutting a diameter you can be off and it'll still be fine, parting is just less forgiving.
    I'm just a startled bunny in the headlights of life. L.J. Young.
    We live in a free country. We have freedom of choice. You can choose to agree with me, or you can choose to be wrong. Me.

  3. #3
    Join Date
    May 2005
    Location
    Newcastle
    Age
    72
    Posts
    864

    Default

    Quote Originally Posted by YarrD View Post
    . I could part off by running lathe in reverse and upside down the parting off tool except
    Bad move tool digs in tool snaps and broken bit flies up at you . have never liked upside down parting off for that reason
    The parting off tool should be set just a touch above centre height to allow for the flex in the tool and post ( it pulls it down to centre height as it cuts)
    If you have power cross feed use it to part off , ( you get far more tool breaks if its hand fed)
    Lock the saddle when parting off
    To find centre height wind the parting off tool in and place a 6" rule vertically against the job , keep winding till the tool just holds the rule in place, if the rule is verticle your at centre height , if the rule is at a slight angle you are either a touch above or below centre height adjust and get the centre height right most important
    Grind a slight taper across the cutting edge so one side of the parting off tool gets to the centre first , this leaves a small dimple on either the section parted off or the remaning stock , but it gives you a clean cut and the dont get the bit being parted off in a wiggle or damaged
    If its a large diam remember you need to run at a higher speed as you get to the centre to keep the cutting speed up , ie part 1/2 way in , withdrar the tool , change speed and then finish parting off
    Have fun , parting off is always an adrenalen rush
    Ashore




    The trouble with life is there's no background music.

  4. #4
    Join Date
    Jan 2009
    Location
    Captains Flat
    Age
    71
    Posts
    122

    Default thanks

    Thanks to all advice on parting off....I am going to give it a go - fingers crossed

  5. #5
    Join Date
    Nov 2007
    Location
    Mt Crosby, Brisbane
    Posts
    177

    Default

    If you've got some brass that's a good material to try first. Stiffer than aluminium but softer than steel and chips rather than making long swarf tails. Keep your tool as close to the post as you can and part as clos to the chuck as you can and generally keep everything as stiff as you can. Should be fine.

    2c.
    I'm just a startled bunny in the headlights of life. L.J. Young.
    We live in a free country. We have freedom of choice. You can choose to agree with me, or you can choose to be wrong. Me.

  6. #6
    Join Date
    Sep 2008
    Location
    Prince George BC Canada
    Posts
    89

    Default lube

    A key point to parting operations which gets neglected is ....... USE CUTTING OIL!
    The 3 main things you can do to increase your success rate are:
    1, The most rigid setup you can do. (close to chuck, shorten tool as much as you can,maybe even use a tailstock centre)
    2, slow your rpm down
    3, use cutting oil liberally!
    Remember if the ID exceeds the OD the hole will be on the outside!

  7. #7
    Join Date
    May 2005
    Location
    Newcastle
    Age
    72
    Posts
    864

    Default

    Quote Originally Posted by damian View Post
    If you've got some brass that's a good material to try first. Stiffer than aluminium but softer than steel and chips rather than making long swarf tails. Keep your tool as close to the post as you can and part as clos to the chuck as you can and generally keep everything as stiff as you can. Should be fine.

    2c.
    brass you need a negative rake on the tool , its a POP to part off
    Ashore




    The trouble with life is there's no background music.

  8. #8
    Join Date
    May 2005
    Location
    Newcastle
    Age
    72
    Posts
    864

    Default

    Quote Originally Posted by aljunk View Post
    2, slow your rpm down
    !
    This is not a good idea . cutting speed for parting off should be

    Suggested Surface Speeds
    Stainless Steel 45m/min
    Mild Steel 70m/min
    Cast Iron 90m/min
    Brass/Bronze 160m/min
    Aluminium 200m/min


    Where rpm = surface speed in mm x ( pi x diam of the job )
    Ashore




    The trouble with life is there's no background music.

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