How do you drill concentric holes of different diameters on a drill press?

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Often times I need to drill maybe a 1/4" hole, all the way through the piece, and then a 3/8" or 1/2" hole half way through the piece in the same spot. It is often imperative that these holes are exactly concentric.



With a smaller drill press, you cannot just keep the workpiece clamped in place because to remove the smaller bit and replace it with a larger bit (or vice-verse) will end up breaking the alignment and it's nearly impossible to get it back again (within a few thousandths of an inch) by eye.



Are there special drill bits or guides for this purpose?










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  • The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
    – Graphus
    Nov 19 at 8:22






  • 3




    ......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
    – Graphus
    Nov 19 at 8:25















up vote
4
down vote

favorite












Often times I need to drill maybe a 1/4" hole, all the way through the piece, and then a 3/8" or 1/2" hole half way through the piece in the same spot. It is often imperative that these holes are exactly concentric.



With a smaller drill press, you cannot just keep the workpiece clamped in place because to remove the smaller bit and replace it with a larger bit (or vice-verse) will end up breaking the alignment and it's nearly impossible to get it back again (within a few thousandths of an inch) by eye.



Are there special drill bits or guides for this purpose?










share|improve this question









New contributor




AgmLauncher is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.



















  • The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
    – Graphus
    Nov 19 at 8:22






  • 3




    ......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
    – Graphus
    Nov 19 at 8:25













up vote
4
down vote

favorite









up vote
4
down vote

favorite











Often times I need to drill maybe a 1/4" hole, all the way through the piece, and then a 3/8" or 1/2" hole half way through the piece in the same spot. It is often imperative that these holes are exactly concentric.



With a smaller drill press, you cannot just keep the workpiece clamped in place because to remove the smaller bit and replace it with a larger bit (or vice-verse) will end up breaking the alignment and it's nearly impossible to get it back again (within a few thousandths of an inch) by eye.



Are there special drill bits or guides for this purpose?










share|improve this question









New contributor




AgmLauncher is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











Often times I need to drill maybe a 1/4" hole, all the way through the piece, and then a 3/8" or 1/2" hole half way through the piece in the same spot. It is often imperative that these holes are exactly concentric.



With a smaller drill press, you cannot just keep the workpiece clamped in place because to remove the smaller bit and replace it with a larger bit (or vice-verse) will end up breaking the alignment and it's nearly impossible to get it back again (within a few thousandths of an inch) by eye.



Are there special drill bits or guides for this purpose?







drilling drill-bits






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edited 2 days ago









Kromster

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asked Nov 18 at 23:34









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  • The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
    – Graphus
    Nov 19 at 8:22






  • 3




    ......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
    – Graphus
    Nov 19 at 8:25

















  • The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
    – Graphus
    Nov 19 at 8:22






  • 3




    ......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
    – Graphus
    Nov 19 at 8:25
















The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
– Graphus
Nov 19 at 8:22




The woodworking guides suggest this is actually very simple, you are supposed to be able to replace a smaller bit with one or more larger bits without moving the workpiece and breaking alignment. But this ability obviously depends on the design of the drill press and on the length of some or all of the bits being used and how they relate to the workpiece height. Now that said, saying you need a bigger drill press isn't really a viable answer! And there are other means to ensure you get near-perfect concentricity no matter which hole you drill first BUT....
– Graphus
Nov 19 at 8:22




3




3




......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
– Graphus
Nov 19 at 8:25





......you're asking too much of the material to achieve accuracy within a few thousandths of an inch every time. Especially with softer woods, especially including most common softwoods, the wood itself just won't allow this (even with the best equipment in the world). Accuracy in the range of a couple hundredths is all you can realistically expect sometimes, because wood is inherently variable (and occasionally contrary) stuff!
– Graphus
Nov 19 at 8:25











4 Answers
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up vote
5
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Forstner bits have a small point on the end which leaves a slight indentation in the wood in the center of the hole. Use this to align your drill bits after changing them. But, to do this, you'll have to drill them the opposite way you're thinking - drill the biggest (but shallowest) hole first, followed by the next smallest / deepest. This keeps that slight indentation from the point on the drill bit present in the wood, allowing you to align the next drill bit.






share|improve this answer




















  • I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
    – AgmLauncher
    Nov 19 at 2:45







  • 1




    @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
    – Ast Pace
    Nov 19 at 18:28

















up vote
3
down vote













You can drill the smaller through-hole first, then use a counterbore tool. The end of the counterbore will use the through-hole as a guide and will cut a flat-bottomed hole of a larger size exactly centered on the smaller hole.






share|improve this answer








New contributor




MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
























    up vote
    3
    down vote













    Similar to the other answers, but for any drill bit type:



    1. Drill a very small pilot hole deeper than the shallowest, big diameter hole. Use a standard twist bit. Limit depth if this is to be a stopped (not through) hole.

    2. Use your small pilot hole to center the new bit while you drill the largest diameter, shallowest hole.

    3. Use your small pilot hole to center the new bit while you drill the next smaller diameter, slightly deeper hole.

    4. Lather, rinse, repeat until you have the smallest, deepest hole.

    If you use, say a 1/16" bit for your pilot hole, your 1/2", 3/8", and 1/4" bits of any sort should line themselves up quite nicely on that 1/16" hole.



    Additionally, as Graphus pointed out in his comments on the OP accuracy within a few thousandths is highly unlikely with home- or even commercial-grade woodworking drill presses. You'd likely need an expensive CNC drill press to achieve that accuracy and a much harder, or at least much more consistent material (plastic or metal) to achieve that kind of precision.






    share|improve this answer


















    • 1




      Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
      – Graphus
      2 days ago










    • @Graphus that's why I said you said it! ;)
      – FreeMan
      2 days ago










    • I meant the final final one :-) re. plastic or metal.
      – Graphus
      yesterday


















    up vote
    0
    down vote













    If you use brad point drill bits drill the larger one first then carefully center the smaller one over the point (left in the hole) of the larger one then drill through. OR Drill a very small hole as a center point through the board use this as a center for the 1/4" and the 3/8" hole.






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      4 Answers
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      active

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      4 Answers
      4






      active

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      active

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      active

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      up vote
      5
      down vote













      Forstner bits have a small point on the end which leaves a slight indentation in the wood in the center of the hole. Use this to align your drill bits after changing them. But, to do this, you'll have to drill them the opposite way you're thinking - drill the biggest (but shallowest) hole first, followed by the next smallest / deepest. This keeps that slight indentation from the point on the drill bit present in the wood, allowing you to align the next drill bit.






      share|improve this answer




















      • I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
        – AgmLauncher
        Nov 19 at 2:45







      • 1




        @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
        – Ast Pace
        Nov 19 at 18:28














      up vote
      5
      down vote













      Forstner bits have a small point on the end which leaves a slight indentation in the wood in the center of the hole. Use this to align your drill bits after changing them. But, to do this, you'll have to drill them the opposite way you're thinking - drill the biggest (but shallowest) hole first, followed by the next smallest / deepest. This keeps that slight indentation from the point on the drill bit present in the wood, allowing you to align the next drill bit.






      share|improve this answer




















      • I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
        – AgmLauncher
        Nov 19 at 2:45







      • 1




        @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
        – Ast Pace
        Nov 19 at 18:28












      up vote
      5
      down vote










      up vote
      5
      down vote









      Forstner bits have a small point on the end which leaves a slight indentation in the wood in the center of the hole. Use this to align your drill bits after changing them. But, to do this, you'll have to drill them the opposite way you're thinking - drill the biggest (but shallowest) hole first, followed by the next smallest / deepest. This keeps that slight indentation from the point on the drill bit present in the wood, allowing you to align the next drill bit.






      share|improve this answer












      Forstner bits have a small point on the end which leaves a slight indentation in the wood in the center of the hole. Use this to align your drill bits after changing them. But, to do this, you'll have to drill them the opposite way you're thinking - drill the biggest (but shallowest) hole first, followed by the next smallest / deepest. This keeps that slight indentation from the point on the drill bit present in the wood, allowing you to align the next drill bit.







      share|improve this answer












      share|improve this answer



      share|improve this answer










      answered Nov 19 at 0:44









      mmathis

      1,972530




      1,972530











      • I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
        – AgmLauncher
        Nov 19 at 2:45







      • 1




        @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
        – Ast Pace
        Nov 19 at 18:28
















      • I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
        – AgmLauncher
        Nov 19 at 2:45







      • 1




        @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
        – Ast Pace
        Nov 19 at 18:28















      I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
      – AgmLauncher
      Nov 19 at 2:45





      I've found this does not work with softwood, or plywood because it's very easy for the point of the forster acting as a probe to alter the existing point in the shallower hole. And because the point of the forstner is not conical (but rather, a two-edge blade), it can be quite easy for the alignment to be off by a few thousands of an inch. This can have an adverse effect on the precision of say, a threaded insert or a bushing, often resulting in binding of the screw. Generally the point of a forster is NOT a reliable register for exact concentricity.
      – AgmLauncher
      Nov 19 at 2:45





      1




      1




      @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
      – Ast Pace
      Nov 19 at 18:28




      @AgmLauncher For what it's worth Even though the tip of the Forstner is not conical, the divot that it produces is conical.
      – Ast Pace
      Nov 19 at 18:28










      up vote
      3
      down vote













      You can drill the smaller through-hole first, then use a counterbore tool. The end of the counterbore will use the through-hole as a guide and will cut a flat-bottomed hole of a larger size exactly centered on the smaller hole.






      share|improve this answer








      New contributor




      MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.





















        up vote
        3
        down vote













        You can drill the smaller through-hole first, then use a counterbore tool. The end of the counterbore will use the through-hole as a guide and will cut a flat-bottomed hole of a larger size exactly centered on the smaller hole.






        share|improve this answer








        New contributor




        MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.



















          up vote
          3
          down vote










          up vote
          3
          down vote









          You can drill the smaller through-hole first, then use a counterbore tool. The end of the counterbore will use the through-hole as a guide and will cut a flat-bottomed hole of a larger size exactly centered on the smaller hole.






          share|improve this answer








          New contributor




          MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          You can drill the smaller through-hole first, then use a counterbore tool. The end of the counterbore will use the through-hole as a guide and will cut a flat-bottomed hole of a larger size exactly centered on the smaller hole.







          share|improve this answer








          New contributor




          MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          share|improve this answer



          share|improve this answer






          New contributor




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          answered Nov 19 at 4:02









          MTA

          1311




          1311




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              up vote
              3
              down vote













              Similar to the other answers, but for any drill bit type:



              1. Drill a very small pilot hole deeper than the shallowest, big diameter hole. Use a standard twist bit. Limit depth if this is to be a stopped (not through) hole.

              2. Use your small pilot hole to center the new bit while you drill the largest diameter, shallowest hole.

              3. Use your small pilot hole to center the new bit while you drill the next smaller diameter, slightly deeper hole.

              4. Lather, rinse, repeat until you have the smallest, deepest hole.

              If you use, say a 1/16" bit for your pilot hole, your 1/2", 3/8", and 1/4" bits of any sort should line themselves up quite nicely on that 1/16" hole.



              Additionally, as Graphus pointed out in his comments on the OP accuracy within a few thousandths is highly unlikely with home- or even commercial-grade woodworking drill presses. You'd likely need an expensive CNC drill press to achieve that accuracy and a much harder, or at least much more consistent material (plastic or metal) to achieve that kind of precision.






              share|improve this answer


















              • 1




                Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
                – Graphus
                2 days ago










              • @Graphus that's why I said you said it! ;)
                – FreeMan
                2 days ago










              • I meant the final final one :-) re. plastic or metal.
                – Graphus
                yesterday















              up vote
              3
              down vote













              Similar to the other answers, but for any drill bit type:



              1. Drill a very small pilot hole deeper than the shallowest, big diameter hole. Use a standard twist bit. Limit depth if this is to be a stopped (not through) hole.

              2. Use your small pilot hole to center the new bit while you drill the largest diameter, shallowest hole.

              3. Use your small pilot hole to center the new bit while you drill the next smaller diameter, slightly deeper hole.

              4. Lather, rinse, repeat until you have the smallest, deepest hole.

              If you use, say a 1/16" bit for your pilot hole, your 1/2", 3/8", and 1/4" bits of any sort should line themselves up quite nicely on that 1/16" hole.



              Additionally, as Graphus pointed out in his comments on the OP accuracy within a few thousandths is highly unlikely with home- or even commercial-grade woodworking drill presses. You'd likely need an expensive CNC drill press to achieve that accuracy and a much harder, or at least much more consistent material (plastic or metal) to achieve that kind of precision.






              share|improve this answer


















              • 1




                Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
                – Graphus
                2 days ago










              • @Graphus that's why I said you said it! ;)
                – FreeMan
                2 days ago










              • I meant the final final one :-) re. plastic or metal.
                – Graphus
                yesterday













              up vote
              3
              down vote










              up vote
              3
              down vote









              Similar to the other answers, but for any drill bit type:



              1. Drill a very small pilot hole deeper than the shallowest, big diameter hole. Use a standard twist bit. Limit depth if this is to be a stopped (not through) hole.

              2. Use your small pilot hole to center the new bit while you drill the largest diameter, shallowest hole.

              3. Use your small pilot hole to center the new bit while you drill the next smaller diameter, slightly deeper hole.

              4. Lather, rinse, repeat until you have the smallest, deepest hole.

              If you use, say a 1/16" bit for your pilot hole, your 1/2", 3/8", and 1/4" bits of any sort should line themselves up quite nicely on that 1/16" hole.



              Additionally, as Graphus pointed out in his comments on the OP accuracy within a few thousandths is highly unlikely with home- or even commercial-grade woodworking drill presses. You'd likely need an expensive CNC drill press to achieve that accuracy and a much harder, or at least much more consistent material (plastic or metal) to achieve that kind of precision.






              share|improve this answer














              Similar to the other answers, but for any drill bit type:



              1. Drill a very small pilot hole deeper than the shallowest, big diameter hole. Use a standard twist bit. Limit depth if this is to be a stopped (not through) hole.

              2. Use your small pilot hole to center the new bit while you drill the largest diameter, shallowest hole.

              3. Use your small pilot hole to center the new bit while you drill the next smaller diameter, slightly deeper hole.

              4. Lather, rinse, repeat until you have the smallest, deepest hole.

              If you use, say a 1/16" bit for your pilot hole, your 1/2", 3/8", and 1/4" bits of any sort should line themselves up quite nicely on that 1/16" hole.



              Additionally, as Graphus pointed out in his comments on the OP accuracy within a few thousandths is highly unlikely with home- or even commercial-grade woodworking drill presses. You'd likely need an expensive CNC drill press to achieve that accuracy and a much harder, or at least much more consistent material (plastic or metal) to achieve that kind of precision.







              share|improve this answer














              share|improve this answer



              share|improve this answer








              edited 2 days ago

























              answered Nov 19 at 21:11









              FreeMan

              2,6091129




              2,6091129







              • 1




                Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
                – Graphus
                2 days ago










              • @Graphus that's why I said you said it! ;)
                – FreeMan
                2 days ago










              • I meant the final final one :-) re. plastic or metal.
                – Graphus
                yesterday













              • 1




                Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
                – Graphus
                2 days ago










              • @Graphus that's why I said you said it! ;)
                – FreeMan
                2 days ago










              • I meant the final final one :-) re. plastic or metal.
                – Graphus
                yesterday








              1




              1




              Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
              – Graphus
              2 days ago




              Your final comment was basically what I was going to say to the OP if/when he came back. And even if you can achieve this accuracy in wood, without the wood itself causing a problem, there's little chance that subsequent seasonal movement won't cause an issue at some point down the line (and likely sooner rather than later) if the thing is built to tolerances this high.
              – Graphus
              2 days ago












              @Graphus that's why I said you said it! ;)
              – FreeMan
              2 days ago




              @Graphus that's why I said you said it! ;)
              – FreeMan
              2 days ago












              I meant the final final one :-) re. plastic or metal.
              – Graphus
              yesterday





              I meant the final final one :-) re. plastic or metal.
              – Graphus
              yesterday











              up vote
              0
              down vote













              If you use brad point drill bits drill the larger one first then carefully center the smaller one over the point (left in the hole) of the larger one then drill through. OR Drill a very small hole as a center point through the board use this as a center for the 1/4" and the 3/8" hole.






              share|improve this answer
























                up vote
                0
                down vote













                If you use brad point drill bits drill the larger one first then carefully center the smaller one over the point (left in the hole) of the larger one then drill through. OR Drill a very small hole as a center point through the board use this as a center for the 1/4" and the 3/8" hole.






                share|improve this answer






















                  up vote
                  0
                  down vote










                  up vote
                  0
                  down vote









                  If you use brad point drill bits drill the larger one first then carefully center the smaller one over the point (left in the hole) of the larger one then drill through. OR Drill a very small hole as a center point through the board use this as a center for the 1/4" and the 3/8" hole.






                  share|improve this answer












                  If you use brad point drill bits drill the larger one first then carefully center the smaller one over the point (left in the hole) of the larger one then drill through. OR Drill a very small hole as a center point through the board use this as a center for the 1/4" and the 3/8" hole.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Nov 19 at 23:32









                  Monte Glover

                  602




                  602




















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