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  1. #1
    Join Date
    Oct 2011
    Location
    Sydney, NSW
    Posts
    1,249

    Default Parting Off Blade/Tool Advice

    Hi,

    I finally snapped my Chronos bought parting off tool yesterday on my Hercus.

    I'm looking at replacing it with this:

    SLTBN Parting-off Tool Holders with Blade (Size from 6mm to 16mm) | eBay

    Has anyone used these before on the smaller Hercu/Hobbyist lathes?

    Ben.

  2. #2
    Join Date
    Oct 2011
    Location
    Sydney, NSW
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    Default

    I forgot to add, I'll probably get the 3 mm insert.

    Ben.

  3. #3
    Join Date
    Mar 2009
    Location
    Melbourne
    Age
    54
    Posts
    825

    Default

    G'day Ben,
    I bought one of these a few months ago with a 2mm insert to use on my Hercus 260 and it seems to do the job well enough.
    The tips out of the box cut ok but seem to need a bit more force than a HSS blade, I assume this is normal given they don't really have a sharp cutting edge.
    I've tried regrinding the tips to get a sharper edge and this seems to improve things a bit but I find that a sharper edge can be brittle and break down fairly quickly particularly when parting larger diameter (>1.25") stock.

    I went with a 16mm holder and modified it to mount directly onto an AXA tool post which greatly reduces the overhang and makes the tool more solid.
    All in all, for around $60.00 I'm pretty happy with it.
    For the inserts, I bought twenty from China for around $25.00 but the same seller now has them in larger bulk lots which are much cheaper than through Ausee and the quality seems to be the same as the one supplied with the holder.

    https://www.ebay.co.uk/itm/50pcs-SP2...oAAOSwTM5Yymcg

    Cheers,
    Greg.

  4. #4
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

    Default

    Can't help you with a recommendation, but I'm in a similar situation having broken the only insert in a Sandvik holder/blade I was given. Prior to breaking it due to my own carelessness, it was the only parting tool I've had real success with. Unfortunately the inserts seem to be a Sandvik special and not readily available in less than a full pack (~$150) so I'm very interested in these ones that take the readily available GTN insert.

    Watching with interest

    Steve

  5. #5
    Join Date
    May 2015
    Location
    Richmond
    Posts
    214

    Default

    For general use for any hobbiest lathe work you can't go past a HSS blade. Far cheaper way of doing things and more user friendly on a small lathe. Have a look at the blocks which take HSS blades.

  6. #6
    Join Date
    Apr 2012
    Location
    Healesville
    Posts
    2,129

    Default

    Hi Ben, i use a 4mm GTN x 32mm blade in a homemade parting block on my larger lathe, as mentioned above they can use quite a bit of pressure to actualy start the cut, it feels as though there is a hard skin on the material and once you push through that it cuts like butter. But in saying that some materials are better than others, for example 4140 requires almost no pressure to start cutting as compared to 1020.
    I use a hercus b model with a 3 jaw as a 2nd op lathe, basically i use anytime i can to save me from changing the 4 jaw on the larger lathes, getting to the point this lathe would not handle the GTN cutters, i think that it is likely that when the cutter is pushed with the force required and it pushed through and into cutting mode the "spring" in the lathe would push the tool in too deep and dig in.
    I dont know what speeds other people are running but for me 600 rpm seems to work well and l might slow it down a bit above a 80mm dia job.
    To slow can be worse than too fast with these.
    Cheers, shed

  7. #7
    Join Date
    Jun 2011
    Location
    gold coast
    Posts
    303

    Default

    I have an Eccentric Engineering FoR Inverted parting tool, and for my money its unbeatable.

  8. #8
    Join Date
    Oct 2011
    Location
    Sydney, NSW
    Posts
    1,249

    Default

    Hi,


    This part rules out the EE FoR:

    For lathes with a screw on chuck the parting tool must be used in a rear tool post with the lathe running in the normal direction.

    I have a really old and smaller HSS holder and blade which I'll have to sharpen up and use for the time being.

  9. #9
    BobL is online now Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,182

    Default

    I just use my EE inverted parting tool as a regular mounted parting tool and I found it works really well.

  10. #10
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Quote Originally Posted by OldRustyToolie View Post
    For general use for any hobbiest lathe work you can't go past a HSS blade. Far cheaper way of doing things and more user friendly on a small lathe. Have a look at the blocks which take HSS blades.
    I am with Old RustyToolie on this one.
    When I first obtained my 12x36 lathe I suffered a couple of near pants wetting episodes involving breaking parting off tools. As it happened it was another ex toolmaker, also then a teacher who schooled me on the basics of parting off.
    Since that time I have not suffered a PO tool breakage.

    Points to note.

    * Make sure the tool is sharp
    * Set up to part off as close to the chuck as possible
    * Make sure the tool is dead square (horizontally) to the job
    * Ensure the tool, Tool holder,tool post and carriage are all tightly locked down
    * Ensure that the tool holder overhang is kept as short as possible
    * Set on center height or just a smidgin above if the toolholder/tool post is springy
    * The tool stick out is half the diameter of the job plus a smidgin
    *Watch the cutoff swarf -it should look like a curly C-surface should be smooth
    *Once cutting, keep the feed constant
    * Never use a center to support the offcut side

    On stainless, I use sulphur based lube.

    Grahame

  11. #11
    Join Date
    May 2015
    Location
    Richmond
    Posts
    214

    Default

    Agree on all of the above which Grahame has listed although I never like a tool above centre by any amount (for external work). I do have trade books that indicate that the tool be set "about 5 deg below centre". To explain that, if we were to draw a line from the centre of the work to where the tool contacts the circumference it would be about 5 deg. Spring downward on any tool other than a tangential type results in "dig in" or increased depth of cut. In practice, as near to centre as we can get if parting off solid material. If hollow a bit below doesn't hurt. All it does is increase the front clearance a poofteenth and decreases the back rake by the same amount.

    Now with all that, no one has mentioned clearance and actual rake angles on HSS parting blades. Keep front clearance to max 8 deg but (especially on lighter hobby size machines) have up to 25 deg back rake for soft to medium carbon steel and a bit less, say 10-15 deg for cast iron, more can be used for soft aluminium and near zero for brass. So with this info we can't have a parting tool sharpened for covering all types of material. With a tool holder that takes the HSS blades we can have blades ground with different rakes to be changed out quickly for the various materials we are using.

    Finally, ALWAYS use a cutting oil on all steel and aluminium. That goes for carbide as well as HSS. Make sure the cutting speed is in the range where the chip flows as well. Too many of our fellow machinists run at a low cutting speed which results in the metal crumbling, not flowing which in turn causes "built up edge", a cause of tool failure on carbides.

  12. #12
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Hi OldRustyToolie,

    I may have misremembered that instruction about center height completely. It was over 20 years ago.These days I have trouble remembering what I was told yesterday.

    I remember at school we had an old Asian lathe where the tool post as well, how do I put it, made of peanut paste. I broke tools on it.
    I can sympathise with other blokes that break HSS PO tools as the resultant noise seems like I had broken something inside the machine not the tool.

    With 12 x 36, on the other hand, all I ever did to get centre was put a 6" rule between the job and the cutting points.The height was adjusted until the rule was vertical. A quick change tool post and the appropriate holder later made short work of that task.
    Gotta love quick change tools.Drop them in, lock and go.



    Grahame

  13. #13
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,435

    Default

    Quote Originally Posted by bwal74 View Post
    Hi,


    This part rules out the EE FoR:

    For lathes with a screw on chuck the parting tool must be used in a rear tool post with the lathe running in the normal direction.

    I have a really old and smaller HSS holder and blade which I'll have to sharpen up and use for the time being.
    Hi,
    I'm totally confused by this comment !

    Surely a parting blade mounted in the normal way would cut just the same as a normal lathe tool !
    In a rear mounted tool holder the blade would be mounted upside down !
    How do you get to unscrew the chuck, I've never seen a lathe with a left hand chuck thread.
    Best Regards:
    Baron J.

  14. #14
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Default

    Quote Originally Posted by Grahame Collins View Post
    Hi OldRustyToolie,

    With 12 x 36, on the other hand, all I ever did to get centre was put a 6" rule between the job and the cutting points.The height was adjusted until the rule was vertical.

    Grahame
    That is all I do to check tool hight on my Myford. I do have a QCTP but hardly ever use it.

    Oddly enough I was parting off a chunk of 40 mm diameter bar this afternoon. Rear mounted, inverted 2 mm thick X 15 mm HSS blade, about 450 rpm with Trefolex as cutting lubricant. No problem at all. I think I've posted pictures on here of my set up.
    Best Regards:
    Baron J.

  15. #15
    Join Date
    Oct 2011
    Location
    Sydney, NSW
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    Default

    Thanks for the replies. I've got good service out of the Chronos/Glanze PO tool but I'm not going to replace it (due to cost and time). I broke the last one due to changing the way I usually did parting off (higher speed and a bit faster cut).

    I've only ever used carbide tipped PO tools so are generally comfortable with them.

    Maybe it's time to use a HSS PO tool?

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