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Re: [MedievalSawdust] dril bit tracking tricks?

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  • Bruce S. R. Lee
    If you are drilling a 1.25 inch (30mm+) diameter hole then you would normally use either a Forstner type bit or a hole saw (in a power workshop), both of which
    Message 1 of 7 , Jan 20, 2010
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      If you are drilling a 1.25 inch (30mm+) diameter hole then you would
      normally use either a Forstner type bit or a hole saw (in a power
      workshop), both of which -should- deflect less than a twist bit as
      they have a fair bit of smooth, non-cutting side wall to the bit. The
      Forstner bit in particular is noted for its ability to drill a
      straight & precise hole, even when the timber is angled relative to
      the bit's axis. Smooth rim Forstners should be the least inclined to
      wander, just get a HSS bit and not plain carbon steel as you will be
      heating up the cutting edge a fair bit - I don't know how well the
      saw toothed & 'Maxi-cut' modified Forstners go with wandering over a
      glue line as I've always used them in solid timber .

      You could always laminate the job up from 2 slightly different width
      pieces, so the glue line was offset by a 1/4 inch or so from the center....

      But, I wouldn't bother too much, just clamp the timber down in the
      drill press well so it can't shift, and make sure you have the table
      tightened well too (been there, D'Oh!)

      Also, don't forget to back up the job with a piece of scrap material
      to avoid damage to the rear surface - if you use a Forstner bit you
      don't get much of a hole from the center pin, so there is not much
      chance to turn the job over & complete the hole from the back, as you
      can do with an auger or spade bit.

      I'm probably just stating what you have already considered..

      regards
      Brusi of Orkney
      Rowany/Lochac

      At 11:52 PM 20/01/2010, you wrote:
      >[Attachment(s) from Conal O'hAirt Jim Hart included below]
      >
      >I'm going to be drilling a larger hole ( 1 1/4" )through the width
      >of a 6" piece of yellow
      >pine. see attached file. this piece is going to be glued up along
      >the same plane as the hole
      >and the hole will be centered on the glue joint.
      >
      >I've had some issues with the drill bit wandering off course even in my drill
      >press.
      >
      >What I am wondering is what tricks do you guys know to help keep the bit
      >cutting where I want it to without drifting around when it hits
      >harder and softer
      >areas of the wood?
      >
      >Pre drilling with a smaller bit is only a partial solution unless I
      >buy an extra long
      >smaller bit. Drilling slower and using a new bit I know will help....
      >
      >But I figured I'd ask just in case someone out here knows I trick/technique I
      >do not.
      >
      >
      >
      >
      >
      >Baron Conal O'hAirt / Jim Hart
      >
      >Aude Aliquid Dignum
      >' Dare Something Worthy '
    • Gille MacDhnouill
      If you have a drill press, use a forstner bit - they don t wander. You can get extensions (
      Message 2 of 7 , Jan 20, 2010
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        If you have a drill press, use a forstner bit - they don't wander.
        You can get extensions ( http://www.rockler.com/product.cfm?page=17994&filter=forstner%20bit%20extension ) so you can make the whole 6".
        Of course, if you could chuck it up on a lathe, you could drill it, and true it up with a boring bar.
        -----Gille

        --- In medievalsawdust@yahoogroups.com, Conal O'hAirt Jim Hart <baronconal@...> wrote:
        >
        > I'm going to be drilling a larger hole�( 1 1/4" )through the width of a 6" piece of yellow
        > pine.� see attached file. this piece is going to be glued up along the same plane as the hole
        > and the hole will be centered on the glue joint.
        >
        > I've had some issues with the drill bit wandering off course even in�my drill
        > press.
        >
        > What�I am wondering is�what tricks do you guys know to help keep the bit
        > cutting where I want it to without drifting around when it hits harder and softer
        > areas of the wood?
        >
        > Pre drilling with a�smaller bit is only a partial solution unless I buy an extra long
        > smaller bit.�Drilling�slower and using a new bit I know will help....
        >
        > But�I figured I'd ask just in case someone out here knows I trick/technique I
        > do not.
        >
        >
        >
        >
        > �Baron Conal O'hAirt / Jim Hart
        >
        > Aude Aliquid Dignum
        > ' Dare Something Worthy '
        >
      • Michael Houghton
        Howdy! On Wed, Jan 20, 2010 at 7:52 AM, Conal O hAirt Jim Hart ... A Forstner bit can do the trick, but they don t usually go six inches deep. An Irwin
        Message 3 of 7 , Jan 20, 2010
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          Howdy!

          On Wed, Jan 20, 2010 at 7:52 AM, Conal O'hAirt Jim Hart
          <baronconal@...> wrote:
          >
          > [Attachment(s) from Conal O'hAirt Jim Hart included below]
          >
          > I'm going to be drilling a larger hole ( 1 1/4" )through the width of a 6" piece of yellow
          > pine.  see attached file. this piece is going to be glued up along the same plane as the hole
          > and the hole will be centered on the glue joint.
          >
          > I've had some issues with the drill bit wandering off course even in my drill
          > press.
          >
          > What I am wondering is what tricks do you guys know to help keep the bit
          > cutting where I want it to without drifting around when it hits harder and softer
          > areas of the wood?
          >
          > Pre drilling with a smaller bit is only a partial solution unless I buy an extra long
          > smaller bit. Drilling slower and using a new bit I know will help....
          >
          > But I figured I'd ask just in case someone out here knows I trick/technique I
          > do not.
          >
          A Forstner bit can do the trick, but they don't usually go six inches deep.
          An Irwin Speedbor bit can do the six inch depth, and it's a long, aggressive
          spiral. You don't use it in a drill press, as it has a screw tip that
          helps draw the
          sucker into the wood. The hole won't wander, but it does cut a bit on the
          rough side. They do go up to 1-1/4" diameter. I've used the 7/8 to bore holes
          into 2x4 and found it to work well. I set the cordless drill to the slow speed
          which let me keep control as I hogged out a 3 inch deep hole in a few
          seconds.

          If you get a starter mark (perhaps using a countersink), it should stay
          on the line fine.

          http://www.irwin.com/irwin/consumer/jhtml/detail.jhtml?prodId=IrwinProd160002

          --
          Michael Houghton   | Herveus d'Ormonde
          herveus@...         | White Wolf and the Phoenix
          Bowie, MD, USA            | Tablet and Inkle bands, and other stuff
                                   | http://whitewolfandphoenix.com
        • powell.sean@comcast.net
          From a metal fabrication sense I can say that we have similar problems on deep bores. One solution is gun-drilling but I doubt that you have the capability of
          Message 4 of 7 , Jan 20, 2010
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            From a metal fabrication sense I can say that we have similar problems on deep bores. One solution is gun-drilling but I doubt that you have the capability of spinning the workpiece in the opposite direction simultaneous to spinning the drill-bit.

             

            Lacking that a smooth sided bit is the next best. The longer the sides the better. A fostner is probably your best off-the-shelf solution unless you know someone who can mill you a twist drill with no radial relief. Actually it would be fairly trivial to take a 1 3/8 twist drill and grind it down to 1 1/4 and remove the radial relief if you have the correct tools.

             

            The final option is to drill a smaller diameter hole and then ream it out to the correct size. Reamers should have at least 4" of cutting flutes and some are likely to have 6". A reamed hole will be straight for the length of the reamer and usually for quite a bit more.

             

            Luck!

            Sean


            ----- Original Message -----
            From: "Conal O'hAirt Jim Hart" <baronconal@...>
            To: medievalsawdust@yahoogroups.com
            Sent: Wednesday, January 20, 2010 7:52:29 AM GMT -05:00 US/Canada Eastern
            Subject: [MedievalSawdust] dril bit tracking tricks? [1 Attachment]

            [Attachment(s) from Conal O'hAirt Jim Hart included below]

            I'm going to be drilling a larger hole ( 1 1/4" )through the width of a 6" piece of yellow
            pine.  see attached file. this piece is going to be glued up along the same plane as the hole
            and the hole will be centered on the glue joint.
             
            I've had some issues with the drill bit wandering off course even in my drill
            press.
             
            What I am wondering is what tricks do you guys know to help keep the bit
            cutting where I want it to without drifting around when it hits harder and softer
            areas of the wood?
             
            Pre drilling with a smaller bit is only a partial solution unless I buy an extra long
            smaller bit. Drilling slower and using a new bit I know will help....
             
            But I figured I'd ask just in case someone out here knows I trick/technique I
            do not.
             
             
             

             
            Baron Conal O'hAirt / Jim Hart

            Aude Aliquid Dignum
            ' Dare Something Worthy '


            Attachment(s) from Conal O'hAirt Jim Hart

            1 of 1 Photo(s)

          • John LaTorre
            ... ... You didn t say how tight the tolerances have to be, but I m guessing that you have a little wiggle room. The only thing I can think of is to use
            Message 5 of 7 , Jan 20, 2010
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              Conal O'hAirt wrote:

              >
              > I'm going to be drilling a larger hole ( 1 1/4" )through the width of a 6" piece of yellow
              > pine. see attached file. this piece is going to be glued up along the same plane as the hole
              > and the hole will be centered on the glue joint.
              >
              >
              >

              <snip>
              > But I figured I'd ask just in case someone out here knows I trick/technique I
              > do not.
              >

              You didn't say how tight the tolerances have to be, but I'm guessing
              that you have a little wiggle room. The only thing I can think of is to
              use a Forstner bit instead of a spade bit and take it slow. If you
              really, really trust the trueness of your drill table and your
              marking-out skills, you could bore halfway through on one side, flip the
              work over, and drill the rest of the way from the other side. I've done
              that when boring center hubs for spoke tents. (But in that case, I
              didn't want a tight fit, and if it came off a little wrong, a bit of
              work with a rasp would make the offset go away.)

              Good luck!

              Johann von Drachenfels
              West Kingdom
            • conradh@efn.org
              ... Johann s idea here sounds good to me, along with his warning about careful layout. I d add only that if the hole were made undersize to begin with, from
              Message 6 of 7 , Jan 20, 2010
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                On Wed, January 20, 2010 11:36 am, John LaTorre wrote:
                > Conal O'hAirt wrote:
                >
                >
                >>
                >> I'm going to be drilling a larger hole ( 1 1/4" )through the width of a
                >> 6" piece of yellow
                >> pine. see attached file. this piece is going to be glued up along the
                >> same plane as the hole and the hole will be centered on the glue joint.

                >
                > You didn't say how tight the tolerances have to be, but I'm guessing
                > that you have a little wiggle room. The only thing I can think of is to use
                > a Forstner bit instead of a spade bit and take it slow. If you really,
                > really trust the trueness of your drill table and your marking-out skills,
                > you could bore halfway through on one side, flip the work over, and drill
                > the rest of the way from the other side. I've done that when boring center
                > hubs for spoke tents. (But in that case, I didn't want a tight fit, and if
                > it came off a little wrong, a bit of work with a rasp would make the
                > offset go away.)

                Johann's idea here sounds good to me, along with his warning about careful
                layout. I'd add only that if the hole were made undersize to begin with,
                from both sides as Johann suggests, then the rasp work could correct any
                centering errors without taking the hole over size. Once the hole has
                been correctly adjusted to the desired centerline, enlarge it to final
                size with a big twist drill or reamer. If you're worried about rough
                breakout at the exit wound, do your reaming from both sides as well.

                Another possibility just occurred to me, though I haven't tried it.
                (Which means you should try it on some scrap first!):

                What if you laid out your centerline on each of the mating faces first,
                and then scored it with a saw kerf all along each line? That should keep
                the center point tracking properly through the assembled block.

                Ulfhedinn
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