Double Mirror Right Angle Drilling Guide




Introduction: Double Mirror Right Angle Drilling Guide

Drilling a straight hole can be difficult because you can only see one side of the bit at a time.  Without a lot of practice, many of the holes end up perpendicular in one plane and not so perpendicular in the other.  Drilling with a conventional guide (2 blocks at 90°) works in some applications, but when using short bits there's not enough room.  This is quick, cheap & easy drilling guide will help you bore accurate holes even with small bits.  Using two small mirrors, it works similar to a dressing room mirror to help you view the bit from all angles.  When all the bits are parallel, start drilling.  It's that easy.    

Step 1: What You Need

Basically what you need to make the guide is 2 wood blocks, 2 mirrors and a means of sticking them together.  In my case, I used double stick carpet tape.  If you don't have 2 small mirrors, you will also need a glass cutting kit & a straight edge.  

Step 2: Making the Drill Guide

I happened to have a couple 3/4" thick scraps already glued together from a previous box joint project which was convenient.  But starting from scratch, you'll want to cut your pieces 2 1/2" x 4 3/4" and 3 1/4" x 4 3/4" if using 3/4" material.  If you have precut mirrors, you'll want to cut your boards to match your mirrors.  I like the 3/4" board because it gives the guide a bit more weight and stands nicely.  The measurements aren't exact so use the odds & ends you have lying around.  Even if you've burned some holes in 'em like I did, they'll still work just fine.  Attach the 2 wood pieces together at 90° with glue and a couple screws.

I wasn't able to take pics while cutting the mirrors, but it's very easy on thin glass.  Simply dip the cutter wheel in oil and then run it along a straight edge lined up on your mark.  If it makes a scratchy "fingers on the chalkboard" sound, you doing great.  Light pressure is all it takes to score the mirror which can then be snapped off.  When breaking it, I like to support one side of the glass on my workbench top with the scoreline even with the edge of the bench.  This makes it easy to break the piece by deflecting the other side downward.  It is always a good idea to wear leather gloves & eye protection when cutting glass and mirror.  Remember that one mirror needs to be slightly narrower to accommodate the width of the other mirror (i.e. 2 1/2" wide and 2 3/8" wide if using 1/8" mirror).

Once your glue has dried and your mirrors are cut, attach the mirrors using double stick carpet tape or an adhesive. 

Step 3: Using the Double Mirror Drill Guide

To use the guide simply place it behind the bit and bring all four bits you see into alignment with each other.  In the first picture it is obvious that my bit is not close to 90° in any direction because the bits are not parallel in the mirrors.  In the second picture, you can see I am much closer to 90° although still not perfectly aligned.  Snapping this picture proved to be a bit "testy" but you get the idea.  

The beauty of this simple guide is that you can make adjustments as you drill to keep the bit at 90° to the surface.  While not as precise as a drill press, it is quite accurate when drilling pieces too big for the press.  The other advantage is that the guide is out of the way of the drill allowing the use of any size bit whether large or small.  

I hope this little drill guide will be useful to you.  I look forward to your comments & suggestions!



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    52 Discussions

    Great idea, thanks. I will definitely be making one. I have a drill press and a drill guide jig, but you can't always take those with you or they are cumbersome just to drill one hole. This will make up for all of that and my unsteady hand. Thanks again!


    3 years ago

    Very clever tool for drilling vertically and true

    excellent idea. Will definitely be making one of these. A couple of vertical lines in the center of each mirror might also help as a reference.

    1 reply

    Question, wouldn't you need only 1 line on account of the reflections, or no?

    great idea i dont have a drill press, and this is very cheap and easy,i do have two mirrors for an old cardboard periscope project to make it

    Yours is a brilliant solution to misaligned drilling!!   Even though my drill has a water mark for vertical and horizontal drilling I was never able to do it right until now. I am forever grateful. Any more ideas?

    1 reply

    What a great idea, and so simple! But you thought of it, and my hats off to you. Thanks, I will definitely make this, and perhaps also use it with my drill press since even there it is hard to see all perspectives for precise drilling.

    This will also help with positioning the work piece under a drill on a drill press. I'd like to think of a way to suspend it spring loaded perhaps from the drill press head so that it doesn't have to be positioned each time.

    Also, has mirrored 1/8th inch acrylic that has adhesive on the back. A 12"x12" piece costs about $10.

    Yep, Mag Drills have been around since the 1970's. We used them to drill holes in the middle of very large plates of steel.


    It isn't as compact or portable as your mirrors are though. But once it is setup it is easier to manually operate.

    After drilling far less than half of all 180 holes straight, I certainly appreciate your genius! :) Brilliant idea!

    Great idea! Reflection might be clear enough to work even if you used a cut section of a CD-ROM. Easier to cut than glass and cheaper too. The hinge then could be DUCT tape for a really low cost model to leave in the toolbox.