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  1. #1
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    Default Why did this stop cutting?????

    I have a 180mm diam. piece of G.C.I. mounted in the 4-jaw, and a brand new not cheap 127mm hole saw, (Bi-meatal Coblat) in the tail stock.

    Running the lowest RPM I can achieve (130RPM) it started cutting well, no heat and no chatter, ...... got in about 2.5-3mm and it just stopped cutting.
    The teeth are perfect, sharp as buggery, but I can apply enough pressure to stall the lathe without any sign of further cutting.

    I haven't come across this before, so looking for answers and a solution please.

    Hole Saw cut stalling.jpg

  2. #2
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    Default

    How many of these plugs at 127 mm dia have you down before?

  3. #3
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    Default

    Could be because the gullets of the teeth are filled with CI dust. Once they are full the saw won't be able to cut any more. Have you tried "pecking" at the cut? I.e. frequently withdrawing the hole saw and brushing the teeth clean.
    Chris

  4. #4
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    Default

    Quote Originally Posted by jack620 View Post
    Could be because the gullets of the teeth are filled with CI dust. Once they are full the saw won't be able to cut any more. Have you tried "pecking" at the cut? I.e. frequently withdrawing the hole saw and brushing the teeth clean.
    Not to the point where the teeth are buried in the cut yet, so no, not choked up.

  5. #5
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    Default

    Quote Originally Posted by pipeclay View Post
    How many of these plugs at 127 mm dia have you down before?
    None, but plenty of of other sizes.

  6. #6
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    Default

    Bit late now, but a carbide tipped holesaw would probably be better; significantly fewer teeth and massive gullets would reduce the load and keep the swarf under control.
    https://www.totaltools.com.au/145221...lesaw-h1271270

  7. #7
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    Default

    Quote Originally Posted by ptrott View Post
    Not to the point where the teeth are buried in the cut yet, so no, not choked up.
    Maybe just overstepping the cutting speed at your stated rpm. HSS tools on cast iron is around 22 m/min so the holesaw that dia should run at around 50 rpm.

  8. #8
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    Default

    Don't know what your lathe is, but first guess would be once you add the drag from the sides of the teeth, your machine just doesn't have the oomph to do it? That size holesaw in cast is a fair bit of load... Second guess would be you've hit a hard spot or inclusion in the cast...

    I assume you're trying to remove a ring around the outside, to keep for another project? What about grinding a grooving tool (with plenty of relief to account for the curve of the groove) and trying that? At the very least, it should open up the region around the holesaw groove a bit, which would allow you to disprove my first guess...

  9. #9
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    Athelstone, SA 5076
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    Default

    Possibly going to deep for the holesaw?

  10. #10
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    Default

    Try coolant, if the cast gets over hot it may be jamming your cutter, could also be the material getting hard due to excessive heat.

  11. #11
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    Quote Originally Posted by Jekyll and Hyde View Post
    Don't know what your lathe is, but first guess would be once you add the drag from the sides of the teeth, your machine just doesn't have the oomph to do it? That size holesaw in cast is a fair bit of load...
    127 x pi is just shy of 400mm circumference ... assuming 4mm tooth pitch, that's 100 teeth ... assuming about 2mm tooth width, that's 200mm of cutting edge to push. You're gonna need a lot of power to do that.

    A TCT holesaw of that diameter might only have 5 or 6 teeth, even if they're a bit wider you're still looking at less than 10% of the power.

  12. #12
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    Quote Originally Posted by elanjacobs View Post
    Bit late now, but a carbide tipped holesaw would probably be better; significantly fewer teeth and massive gullets would reduce the load and keep the swarf under control.
    https://www.totaltools.com.au/145221...lesaw-h1271270
    Swarf was not any part of the issue in this case.
    I did see those, but the description is:

    "H127 Series TCT Multi Purpose Holesaw range can be uses to cut timber, hardwood, softwood, MDF, plaster board, compressed fibre cement sheet, cement sheet, plastics, ceramic tiles and abrasive materials.

    No mention of any metals of any kind at all, which is why I didn't get one.

  13. #13
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    Quote Originally Posted by pipeclay View Post
    Try coolant, if the cast gets over hot it may be jamming your cutter, could also be the material getting hard due to excessive heat.
    No heat, all cool to the touch. Had no issues until I sprayed coolant, lube onto it.

  14. #14
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    Default

    Quote Originally Posted by elanjacobs View Post
    You're gonna need a lot of power to do that.
    But if it cut OK for the first 2-3mm, that implies there’s enough power for the job. If the gullets aren’t filled I’m inclined to agree with the suggestion the saw is jamming in the cut.
    Chris

  15. #15
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    Default

    Still have no idea at all why this happened, but the job is done now.

    Out of desperation I drilled about 20 or so 3.5mm holes in the shallow groove that the holesaw cut before it started skating on the surface.

    That got it started again, and I cut the rest of the depth dry, and very little heat was produced at all, 40-45 degrees according to the laser doohickey.
    It never looked like skating again, just steady cut all the way to 32mm depth.

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