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  1. #21
    Veteran Member carpenter383's Avatar
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    Kioti DK40SE

    Default Re: annular cutters: a better way to drill big holes in thick steel

    What about using a dimmer switch to slow down a DP motor? I know it's generally not a good idea to cut power to a motor, and there would be less available torque. Anyone tried this for occasional use? I have a craftsman benchtop DP and it's slowest speed is 480
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  2. #22
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Universal motors with brushes like on an angle grinder can be controlled that way. HF sells an inexpensive "router" speed controller that works well. Drill presses typically have synchronous AC motors that cannot be speed controlled. If it runs quietly that's what it has.

    3-phase AC motors can be controlled with a variable frequency drive. Small drives with single phase input can be had for about $100-300 at The best way to buy industrial controls--low prices, fast shipping and superior service.

    The problem with just slowing the motor down is that you don't get more torque like you would if you "geared" it lower. Of course on a small drill press adding a bunch of torque would just twist the spindle spline drive and ruin the press.

    Back to the annular cutter thing. I have a few that I grabbed out of a dumpster. They are still in pretty good shape and there was an adapter with them. It's kind of long but it has threads on the back the same as a hole saw. The sizes I have 1", 1.25", and a smaller one I can't remember what size. I haven't really used them because the adapter doesn't fit my drill presses.

    I am experimenting with using my HF pipe notcher guide bolted to a short piece of 6x8x1/2" angle iron that can be clamped to a surface to act as a poor man's "mag" drill. It works good with a hole saw but this thread makes me want to try it with the annular cutters. I'm powering it with a big hand-held drill. I also acquired a chuck like comes with the big HF drill press that goes to 3/4" and I might be able to just chuck up a bare annular cutter.
    2006 Kama 554, 92 Belarus 250AS, Bombardier Outlander Max 400.

  3. #23
    Elite Member dfkrug's Avatar
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Quote Originally Posted by Brad_Blazer View Post
    The problem with just slowing the motor down is that you don't get more torque like you would if you "geared" it lower.
    You are correct that you can not use a speed controller on these DP
    motors. What you CAN do is get a washing machine motor (free!) that
    has 2 speeds and adapt that. When operating a DP at lowest speed, your
    torque multiplication is such that you don't need a strong motor at all. At
    high speeds, you could run into the power limits of the motor, however.

    There is another type of annular cutter out there, which is designed for
    thin metal. I have not seen one up close, so I do not know the differences.
    Anyway, you need a pilot pin or a pilot hole and guide to make these
    work. Otherwise the bit just dances all over the work.

  4. #24
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    2006 Kama 554, 92 Belarus 250AS, Bombardier Outlander Max 400.

  5. #25
    Elite Member dfkrug's Avatar
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Quote Originally Posted by Brad_Blazer View Post
    They also have the drill press adapter $$
    Those look to be very good prices. I have not hear of Travers, but
    I will save the link. Thx for posting.

    Your 3rd link, BRAD, shows the coolant collar that goes over the arbor.
    This is the option I did not buy. If someone goes out and gets this
    option, I hope they report here.

  6. #26
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    I haven't ordered from Travers but the toolroom at work uses them. Their prices and selection seem similar to Enco.

    The picture shows the collar but that's the price without it. It's double that price with the coolant collar. Is there more to it than a tee with o-rings?

    Also note the 2MT is only rated for 1" holes. The 3MT for the same price is rated for 2-3/8" holes.
    2006 Kama 554, 92 Belarus 250AS, Bombardier Outlander Max 400.

  7. #27
    Gold Member
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Can these annular cutters be sharpened when neccessary?

    Or don't they get blunt if you keep the cutting fluid up to them.

  8. #28
    Silver Member
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Quote Originally Posted by allenr View Post
    Can these annular cutters be sharpened when neccessary?

    Or don't they get blunt if you keep the cutting fluid up to them.

    Yes they can be resharpened. I send my dull annular cutters to ohio tool for sharpening. Feed speeds and coolants make a big difference in how long cutters stay sharp.

  9. #29
    Silver Member killdozerd11's Avatar
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    The Peoples Republic of California
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    Kabota B7800

    Default Re: annular cutters: a better way to drill big holes in thick steel

    Great post

    I have used these for years mostly on mills or mill drills and mag drills
    since building safes need properly placed holes for the locking pin frames and doors
    Backed my CATMA over your CARMA
    OOPS Clumsy Me.

  10. #30
    Elite Member dfkrug's Avatar
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    Default Re: annular cutters: a better way to drill big holes in thick steel

    Quote Originally Posted by Brad_Blazer View Post
    The picture shows the collar but that's the price without it. It's double that price with the coolant collar. Is there more to it than a tee with o-rings?
    My MT-3 Arbor came from a tool vendor in the UK, for only $55. I found
    much higher prices from the few places I could find this arbor at US
    vendors. The coolant collar was certainly more, and seems to remain
    stationary while the bit rotates.

    I have heard of these being resharpened, but I have not needed it yet.
    At least one web site says if you turn these too slow, that can
    increase the wear. My machinist pals are skeptical of that claim. I run
    slow and cool.

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