When using a cordless drill to make 1/2" holes in 4x4 or 6x6 lumber:
Despite taking my time, I find the holes I drill aren't perpendicular to the board. What can be done to drill better holes?
Off-grid location; no access to electricity or power tools like a drill press. Various applications.
Use a visual guide of some sort. This can be as simple as a carpenter's square to which you'll align your bit by eye. Be sure to check two axes at right angles.
Use an actual guide. This doesn't need to be a fancy tool. If you can create a bore you know to be square with the board in something durable like hardwood, use it to start the rest of your holes. A scrap of two-by is enough for a half inch bit.
Drill halfway from each side. This halves and averages the error. Once the holes are connected, run the bit all the way through, urging it in the correct direction to emerge at the opposing bore face. Starting with a smaller bit and finishing with the final size can reduce interior cavitation.
Practice. Make mental notes of your faulty tendencies. Are you tilting the drill as you press? Are you favoring your dominant eye when you judge vertical? Practice and learn.
A "hack" from years ago was to use a Compact Disc (CD).
Place the CD as if you need to drill the hole through the middle of the disk, with the shiny side outward. For a vertical surface, that may require temporary tape.
Hold up your drill and bit ready to start drilling, but take a moment first to ensure the reflection of the bit in the CD's shiny side is a straight line to the bit you can see directly.
Source: https://www.woodmagazine.com/drills/fine-tune-drill-bit-angle-using-a-cd
Coincidentally the algorithm just turned up:
Further suggestions:
If you have access to something (a drill press for example) that can drill a perpendicular hole, take a block of wood and drill one or more holes with the intended drill bit. When you are in the field, use that block of wood as a guide by clamping it to where you want to drill.
It is easy to see that the thicker the guide block, the more accurate the angle is likely to be. You would choose the thickness based on the drill bit length and lumber thickness, etc. Drill more than one hole because you can move to another when one starts to get worn out and becomes sloppy.
Here is how I usually do it.
Find a piece of scrap wood (2x4 is good). Drill a perpendicular hole through it (the same size as you intend to drill through the larger wood). I use a drill press, but use whatever method you have.
Clamp (or nail) the scrap to the large piece of wood.
Use the wood as a guide to drill through the larger piece.
I used one of the fancy guides like others have shown to drill straight throug the center of a 24" beam (with lots of bit changes, since the guide only has about 8" of depth). This one, for anybody who cares (very high quality): https://www.woodpeck.com/auto-line-drill-guide.html
But there are much cheaper and simpler ones for drilling things like 4x4s: https://www.amazon.com/dp/B0061FY004
BTW: love, love, love the answers with the CDs and other reflective surfaces!
Super simple answer,
If you need level holes in vertical lumber that is already attached, then simply hot glue a level vial on to your drill so that it is level when the drill is at level. such as this one:
If your drilling holes into Lumber on the ground or on a stand then you can hot glue a bullseye level to the back of your drill:
This is definitely not for everyone, but what I would consider doing is to sketch up a drill guide in a CAD program and 3D print it. If hundreds of holes were necessary, then try to find a metal tube with a 0.5" ID and fit that to the print, otherwise just print a few of them. It could be designed to locate on the so-called 6" lumber (about 5.5", I think) with some side rails or whatever.
But a block of scrap wood with a drill press hole through it would be good too, and faster to make.
