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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.

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    Most of us cannot tell a perfect 90 from a 80/85 by eye alone. One reason you can spend days looking at drill guides to help. If the holes need to be perfectly perpendicular, then a guide is the best choice. Most might need a square to set up the first time. Commented Sep 12, 2024 at 22:07
  • I would mention practicing on a scrap pieces of wood and note an failures/error before doing the real piece. Commented Sep 13, 2024 at 14:08
  • Somewhere I once saw a small drill guide that would attach to a drill. It kind of looked to me like a large T-nut. Unlike the larger guides in the answers below, it only helped with perpendicular drilling. It seemed like such a useful tool, but I've never seen or heard of it since. Commented Sep 13, 2024 at 17:31
  • An add-on laser gadget: instagram.com/reel/DMNKJG1A0jv/?utm_source=ig_web_copy_link Commented Jul 21, 2025 at 3:14

12 Answers 12

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  • 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.

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    Using the "halfway" method, with a smaller diameter bit than the final desired size will give you additional guidance as well. Commented Sep 12, 2024 at 15:41
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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.

using a compact disc to help make a straight hole with a drill
Source: https://www.woodmagazine.com/drills/fine-tune-drill-bit-angle-using-a-cd

Coincidentally the algorithm just turned up:

https://www.youtube.com/watch?v=E-glhRXBMa4&t=613

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    I don't get the hack but maybe I am overthinking. If the hole is smaller than the middle of the cd then how does it help? If the hole is bigger than the cd how does it help? I think when I first saw this I thought you were drilling through the cd itself. Commented Sep 16, 2024 at 0:05
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    @DMoore the CD hole size would limit the hole diameter that can be drilled, but with a mandated size of 15mm its big enough for OP's 1/2" or any reasonable pilot drill. The CD helps with the reflection - your eye is very good at spotting if something is in-line or not. If the drill bit and its reflection are not direct continuations of each other, then the drill is crooked. Check again from above or below to correct in the Y direction. Try it and see for yourself how it works. Commented Sep 16, 2024 at 1:41
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    One aspect that isn't mentioned is that you'd need to check on two different axes. If the drill is leaning directly toward the eye, for example, it'll still appear as a straight line. Commented Sep 16, 2024 at 13:16
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There is a tool out there called a drill guide that might help.

enter image description here

enter image description here

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    In an off-grid application, they may be using a hand drill which requires both hands. Both drill guides shown here appear to have 4 holes in the base you could use to hold it in place if you're unable to hold the handle at the same time. Commented Sep 13, 2024 at 13:19
  • That is a little bit overkill unless you are manufacturing furniture. Commented Sep 13, 2024 at 15:22
  • @DMoore, and get in the way of certiain locations... but you want, want a perpendicular whole, and not an almost perpendicular whole.. This is how to do it. Commented Sep 13, 2024 at 16:48
  • No I agree. It just seems like the guy is building a deck and wants to know a way to drill holes better with his cordless drill. It is good that the tool is shown but realistically 99% of homeowners don't require this nor would they have room for it. I drill way way way more holes than the average homeowner and I haven't even thought about buying one for a split second. Commented Sep 13, 2024 at 19:13
  • Maybe could clamp it down with c clamps to free up hands? :) Commented Sep 13, 2024 at 20:37
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  • Mark the spot on both sides exactly.
  • lay lumber down with one of the marks facing up.
  • drill straight down into the lumber half of its depth - usually with drilling straight down you can stay perpendicular much easier
  • flip it over and do the same to the other side
  • flip it over and go all the way through. You may need to edge drill but should not be using much force.
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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.

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    .. and If there's no drill-press around, just buy the guide block. Commented Sep 13, 2024 at 9:05
  • Or get a selection of ideas here Commented Sep 13, 2024 at 9:32
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Further suggestions:

  • drill a hole in a piece of mirrored plastic, put that on the workpiece and align the drill so it is straight with its reflection, then it will be perpendicular to the workpiece.
  • use a laser level with vertical beam pointing at the bit to give you a reference in one axis; usually I find that I'm good enough left/right so use the laser for forward/backward.
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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:

Level Vial

Example of level on Drill

If you're 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:

Bullseye level

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  • My first drill had both style levels on it, but I haven't seen them built in since then. Commented Sep 19, 2024 at 17:46
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Here is how I usually do it.

  1. 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.

  2. Clamp (or nail) the scrap to the large piece of wood.

  3. Use the wood as a guide to drill through the larger piece.

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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!

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A technique on Instagram where one person uses a long drill bit to drill and the other person holds up two speed squares as guides.

enter image description here

https://www.instagram.com/reel/DMn02pVCSbV/?utm_source=ig_web_copy_link

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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.

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  • Why CAD and 3-D print something that can be purchased relatively inexpensively at higher precision and durability? Commented Sep 13, 2024 at 22:29
  • @Reid Yes, to get it now (or right after dinner) at negligible cost in time or materials. It would be more than 'good enough'. I've done that with a number of jigs and fixtures and it has generally worked out quite well. In my case, I have metalworking capability (drill, mill, engine lathe, grinders, TIG welder, shear etc.), but 3D printing is so easy and fast. Commented Sep 14, 2024 at 4:39
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For cases where we only need the hole to be perpendicular in one axis, such as from side-to-side, but not front-to-back, then visually lining up a line on the top of the drill with a line on the workpiece seems to be an option.

For example, when pre-drilling the ribs on roofing metal (22 sheets, not all shown in the photo) I needed the hole to be perpendicular from side-to-side so that the holes remained in the peak of the rib. But I wasn't as worried about the holes being perpendicular from front-to-back along the rib (that would have been nice, I just didn't have that luxury).

So, I stood behind the drill and visually lined up a line on the plastic moulding at the end of the drill with the rib line behind the drill. I also kept an eye on the line formed by the drill bit.

enter image description here

That worked well. All of the holes were within the peak of the rib.

With that said, this might not be accurate enough for thicker workpieces.

Edit:

Punching instead of drilling might have been a better option:

How to Build a Garage #6 Metal Siding - RR Buildings (YouTube 7:31)

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