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Thread: relief grind on parting tool

  1. #11
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    Quote Originally Posted by jmm03 View Post
    Sorry, the relief I was talking about is clearance on the leading edge (the cutting edge) The tool I am using is brand new, it has clearance under the cutting edge but appears square with no relief on the front. Thanks to all so far. Jim
    That's OK..... we get carried away here sometimes.

    JL.................

  2. #12
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    Quote Originally Posted by boslab View Post
    In short, yes, it’s better (imho) to leave a pip on stock than part, so a slight angle on the front allows the tool tip to reach centre on the RH side, leaving a pip on the stock, immaterial if your parting hollow I suppose, it seems to reduce the cutting force, and the grab tendency of an old sloppy lathe (mine) I’ve forgot it a few times and watched the part climb the tool ( irritating)
    Carbide tips seem to come already profiled unless you specifically order square ones for grooving ( pays to use the right one, interesting lesson when the part is wrong and a ring doesn’t fit I suppose.
    It just needs a touch of angle, couple of degrees.
    Swarf or chips are more inclined to roll up and exit the gullet than an oblique(is that right?) tool too.
    By enlarge I swear tooling ends up weighing more than the lathe!, somthing like photography, a camera body an 20 lbs of lenses.
    Mark
    Until I replaced my cross slide screw and nut I was terrified to part anything. My old screw had about .100 lash in it and everytime I went to part something the tool would get pulled into the work and break. After replacing the screw and nut I've never had a problem.

    And yes...... most of my parting tools I grind out of HSS bits. They don't drift.

    JL.............

  3. #13
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    Not sure what rake is being asked about.... But a flat horizontal top does not seem to cause much problem with the carbide, or with a tool ground from an HSS tool blank. I tend not to use the traditional blade type tools.
    1601

    Keep eye on ball.
    Hashim Khan

  4. #14
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    I must admit I forgot to lock the carriage a while back, not the prettiest parting I’ve seen, I’ve done it and got away with it but that’s rare.
    Eliminating backlash is as said vital!, otherwise it’s the reciprocating parting tool (hacksaw!)
    Mark

  5. #15
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    Quote Originally Posted by boslab View Post
    Eliminating backlash is as said vital!, otherwise it’s the reciprocating parting tool (hacksaw!)
    Mark
    are you guys grinding in some high rake angles? That might be the issue....unless there is an antibacklash nut (ahhhh the DSG ) there going to be backlash on the feedscrew. I can see with too much rake it would pull in. I vaguely remember something like that but with zero or modest rake it doesn't seem to, or at least that's the memory of it before I switch to carbide
    .

  6. #16
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    Quote Originally Posted by boslab View Post
    otherwise it’s the reciprocating parting tool (hacksaw!)
    Mark
    I usually finish the last 6mm/ 1/4 inch or so with the hacksaw.
    It is interesting that we were taught in Australia in 60's , if right handed, to do the hacksaw and lathe file with the left arm over the spinning chuck. I still do that because it is awkward to hacksaw opposite handed.
    I wonder what is taught these days?

  7. #17
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    Quote Originally Posted by dalee100 View Post
    I can't recall seeing any 3mm wide inserts being handed for example.
    Sandvik has them. In fact, it's the first letter of the insert part number (R, N or L). Here is a right-handed 3mm insert

    https://www.sandvik.coromant.com/en-...2005-7e%201125



  8. #18
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    I have about 12 thou backlash, something like that, and parting is not a big issue. Maybe super deep ones could be a problem, I do not part 4" rounds on the 10" machine.....

    if you grind a steep back rake, the tool might get sucked-in and cause issues. A good reason for a flat top tool.

    I have both 3mm and 1.5mm parting insert tools. I need to find more inserts, but that's another matter.
    1601

    Keep eye on ball.
    Hashim Khan

  9. #19
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    Quote Originally Posted by wombat2go View Post
    ... It is interesting that we were taught in Australia in 60's , if right handed, to do the hacksaw and lathe file with the left arm over the spinning chuck. ...
    Being right handed, I'll admit that might be more comfortable. Having said that, I suck it up and stand to the right of the spinning chuck so all of
    my body parts are clear of it.

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