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 Nov 20 at 14:13









Kromster

226110




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asked Nov 18 at 23:34









AgmLauncher

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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












5 Answers
5






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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
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
      Nov 20 at 8:01










    • @Graphus that's why I said you said it! ;)
      – FreeMan
      Nov 20 at 14:46










    • I meant the final final one :-) re. plastic or metal.
      – Graphus
      Nov 21 at 7:32




















    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













      Are you able to drill the bigger hole first?



      That way there will still be some wood there to hold the smaller drill bit, and the pointy pilot tip in the middle will act as a center.



      If the workpiece is too thin, try clamping a scrap piece below the planned hole to give the pilot tip somewhere to indicate onto.






      share|improve this answer





















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        5 Answers
        5






        active

        oldest

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        5 Answers
        5






        active

        oldest

        votes









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        active

        oldest

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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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            MTA is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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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
                  Nov 20 at 8:01










                • @Graphus that's why I said you said it! ;)
                  – FreeMan
                  Nov 20 at 14:46










                • I meant the final final one :-) re. plastic or metal.
                  – Graphus
                  Nov 21 at 7:32

















                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
                  Nov 20 at 8:01










                • @Graphus that's why I said you said it! ;)
                  – FreeMan
                  Nov 20 at 14:46










                • I meant the final final one :-) re. plastic or metal.
                  – Graphus
                  Nov 21 at 7:32















                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 Nov 20 at 14:48

























                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
                  Nov 20 at 8:01










                • @Graphus that's why I said you said it! ;)
                  – FreeMan
                  Nov 20 at 14:46










                • I meant the final final one :-) re. plastic or metal.
                  – Graphus
                  Nov 21 at 7:32
















                • 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
                  Nov 20 at 8:01










                • @Graphus that's why I said you said it! ;)
                  – FreeMan
                  Nov 20 at 14:46










                • I meant the final final one :-) re. plastic or metal.
                  – Graphus
                  Nov 21 at 7:32










                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
                Nov 20 at 8:01




                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
                Nov 20 at 8:01












                @Graphus that's why I said you said it! ;)
                – FreeMan
                Nov 20 at 14:46




                @Graphus that's why I said you said it! ;)
                – FreeMan
                Nov 20 at 14:46












                I meant the final final one :-) re. plastic or metal.
                – Graphus
                Nov 21 at 7:32






                I meant the final final one :-) re. plastic or metal.
                – Graphus
                Nov 21 at 7:32












                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






















                        up vote
                        0
                        down vote













                        Are you able to drill the bigger hole first?



                        That way there will still be some wood there to hold the smaller drill bit, and the pointy pilot tip in the middle will act as a center.



                        If the workpiece is too thin, try clamping a scrap piece below the planned hole to give the pilot tip somewhere to indicate onto.






                        share|improve this answer

























                          up vote
                          0
                          down vote













                          Are you able to drill the bigger hole first?



                          That way there will still be some wood there to hold the smaller drill bit, and the pointy pilot tip in the middle will act as a center.



                          If the workpiece is too thin, try clamping a scrap piece below the planned hole to give the pilot tip somewhere to indicate onto.






                          share|improve this answer























                            up vote
                            0
                            down vote










                            up vote
                            0
                            down vote









                            Are you able to drill the bigger hole first?



                            That way there will still be some wood there to hold the smaller drill bit, and the pointy pilot tip in the middle will act as a center.



                            If the workpiece is too thin, try clamping a scrap piece below the planned hole to give the pilot tip somewhere to indicate onto.






                            share|improve this answer












                            Are you able to drill the bigger hole first?



                            That way there will still be some wood there to hold the smaller drill bit, and the pointy pilot tip in the middle will act as a center.



                            If the workpiece is too thin, try clamping a scrap piece below the planned hole to give the pilot tip somewhere to indicate onto.







                            share|improve this answer












                            share|improve this answer



                            share|improve this answer










                            answered 18 hours ago









                            Criggie

                            1333




                            1333






















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