By swirt on April 19, 2010 at 3:34 pm in techniques •
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When you need to drill straight, and by that I mean plumb to the surface … err even more precisely I mean Normal to the surface, the drill press really is the best tool for the job. And even if the wood can’t be brought to the drill press, a hand drill press can be brought to the wood.
These are two good options for drilling plumb (Normal) to a surface.
However, there are plenty of times when neither of these devices will work for a variety of reasons
You don’t have a press.
You are using a bit and brace
The job at hand doesn’t require that level of precision
You are too far from the shop to go get it
There is a pretty simple solution that satisfies any of these situations. Keep an old CD in your drill case. Place the cd, shiny side up with the hole in the middle of the CD, surrounding your mark for where the hole needs to be bored. Use the reflection of your drill bit to align your bit. The reflection and the actual bit should form a continuous line. If you see a bend, then the bit is not Normal to the surface. By tilting the bit back and forth a little you will see what needs to be done to make the reflection straight. When the reflection is straight, start drilling and use the reflection to keep you on track.
Here is the CD method in action with both a power drill and a brace. The one on the right is intentionally off Normal so you can see that the reflection is not in-line with the bit. Due to the flash and lighting in the photo it is hard to make out the reflection of the bit in the CD. It is much easier to see when it is actually in front of you.
The same method can be used with an acrylic mirror and can be a little more precise with the mirror. There is no need to drill a hole in the center of the mirror, simply place the mirror next to the bit and you will be able to see the reflection. You could also use a glass mirror but I don’t recommend it. Glass is too easily broken and then you have to stop work to clean up your mess, AND look for another mirror.
I like the CD method for a handful of reasons:
They are abundant, so I if one gets scuffed up so much that I can’t use it, I grab another one.
They are re-used garbage.
You can drill them out if you have large holes to bore. (though the hole is not essential)
They come with their own little sleeves or cases to keep them from getting all scratched up while riding in your drill box.
It is just a very fast system to use.
CD Drilling Tips:
I find the bluish ones (re-writables) are the best choice for using them outside.
If you have an angled hole to drill, you can tape a shim to the back of the CD that matches the angle from the Normal and then the reflection will guide you to that angle.
I have seen a similar post of drawing cross hairs at right angles that intersect at a hole in a mirror used for timber framing. I’m not convinced the lines are necessary, but they can’t hurt anything. So if you want the lines, you can draw them on the CD with a sharpie. Here is a video the cross-hair mirror in action.
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