Making a Drill Guide

Sometimes it is necessary to drill a hole at an exact angle, for example when making a propeller or nose block.  This is easy to do if you have access to a drill press, but many do not.  I will show you how to make a drill guide using simple materials and tools.

Here you see the drill guide being set up to drill a 1/16″ diameter hole for a propeller hub. The hole must be exactly perpendicular to the face of the block.  The guide consists of four right triangles glued together to form a 1/16″ hole perpendicular to the four base legs.  You could use this guide placed on an angled plate to drill at other than a right angle, for example, to form side thrust or down thrust in a nose block.

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My first drill guide of this type was made from sturdy cardboard from a large size cereal box.  I took the pictures of that build that you see here.  This proved to be very successful, but cardboard is somewhat soft and must be handled very carefully.  Later I made another from 1/16″ plywood that is more robust.  I used slightly different dimensions.  The triangles were 3/4″ x 3/4″ instead of 3/4″ x 1″.   I recommend that you use plywood or a similar hard material for your drill guide.  You can start by cutting out a 3/4″ x 1 1/2″ piece, cut that into two 3/4″ x 3/4″ pieces and cut each of those on a diagonal to form the four triangles used.  Sand the edges perfectly square.  If you cut with a saw, make allowances for the width of the saw kerf.

There are several ways to mark out the triangles.  This is the way I did my first one.  There are better ways to do it, but I don’t have photos to show them.  After you see this, you can figure out another way more to your liking.  Cardboard is cheap, but you might want to avoid wasting plywood.

I started with a layout line.

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I set up a perpendicular line with drafting triangles.  Anything with a square corner will work here.

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Next I drew the perpendicular line with a sharp pointed pencil.

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I marked 1″ out both ways from the crossing on one line.

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I marked 3/4″ out both ways from the crossing on the other line.  On my plywood guide, I made all four edges 3/4″.

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I cut out around the marked out area.

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I cut along the lines to make four quadrants.

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I cut between the marks on the lines to make four equal 3/4″ x 1″ right triangles.

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I marked 1/16″ from the 3/4″ edge.  Unlike what is shown here, all four triangles should be oriented so they will lie exactly on top of each other.  I made it 1/16″ because this will determine the size of the hole in the center and I am going to use this to guide a 1/16″ diameter drill.  For a 1/32″ drill, I put a length of brass or aluminum tube into the hole, with an outside diameter of 1/16″ and an inside diameter of 1/32″.

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I drew a line through the mark parallel with the 3/4″ edge.

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I put glue along the surface of the edge.

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I glued it to one of the other triangles right behind the line so it was 1/16″ away from the edge.

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I checked that all the angles were square and the bases were even.

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I made another pair in exactly the same way and set them aside to let the glue dry completely.

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I applied glue to the remaining edges on each piece.

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I aligned the pieces and pressed them together.

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I checked that everything was square and that all four bases would lie flat on a flat surface.

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The dimensions were chosen to fit the length of my 1/16″ diameter drill.  When the drill is mounted in the bit, it must project enough beyond the drill guide to make a good start into the wood.  Once it is about 1/2″ into the wood, the hole itself will guide the drill the rest of the way through.

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One thought on “Making a Drill Guide

  1. Hi there,

    I am just getting back into aeromodelling having just retired. The above is one really useful bit of help, as I do not ave a drill press and had been trying to eyeball my centre holes. it is 50 years since I last handcarved a prop so this and your prop carving tutorial have saved a bucketful of tears.

    THanks a lot

    Dave

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