How to not drill too deep

Sometimes when you’re working on a project, you have to drill a hole to a certain depth, and you don’t want to go completely through your workpiece. How do you not drill too deep? Here’s how.

To not drill too deep, you need to stop the drill from going any further than you want. You can use something called a drill stop to do this, or you can improvise your own with stuff you probably have in your shop.

Why you’d need to drill to a certain depth

How to not drill too deep
I got this drill stop set at Harbor Freight for about $5. It slips onto your drill bit, making it impossible to drill too deep.

Usually it’s fine if you drill all the way through your work. But there are cases when you don’t want to. One example would be when making shelves. You want to drill holes about halfway through your sides so you can put your shelf brackets in, but it would look amateurish if you drilled all the way through.

If you’re restoring or customizing diecast cars, sometimes you have to drill out a post so you can tap it for a screw. That’s another case where you don’t want to drill all the way through. You damage the car, and could injure yourself. For that kind of use, it could be a matter of personal safety.

A final example I can think of comes from retro computing. The Commodore 64 case has plastic standoffs on it that are prone to crack and break. You can glue replacements in. Most people recommend drilling all the way through, since many consumer electronics do have exposed screws on the underside. But Commodore didn’t do it that way, and if you’re restoring a rare model, like a silver label C-64, you want the outside to look the way Commodore did it.

Whether you use commercial tools or improvise depends on whether you can get the tool, and whether you can get the size you need. But you have options regardless.

Drill holes to a certain depth with a commercial drill stop

Drill stops are metal rings that clamp onto your drill bit and use a set screw to hold them in place. Just set one to the depth you want, tighten the screw, and it grips on tight, not letting you drill any further. When you’re done, loosen the set screw, and slide off the stop.

These aren’t something you’re likely to find at your home center. And you can pay $30 or more for a set from a specialty supplier. I got mine at Harbor Freight for about $5. Is it as good as a set that costs six times as much? Of course not. Is it good enough for occasional use? Absolutely. For the price, these are a no-brainer. The trouble they save you could be worth the cost with a single use.

Improvise your own drill stop

drill a hole to a certain depth
When you have no other options, you can use a piece of tape to ensure you drill a hole to a certain depth. Just wrap it around to form a flag.

Before I found a drill stop set at Harbor Freight, I used to improvise my own with tubing. And this is a good option if you need to drill a small hole to a certain depth. The smallest stop in my set is 1/8-inch, which is still too big for some of the work I do.

You find a diameter of tubing that fits around your drill bit. Ideally you want a pretty snug fit. Cut the tubing to length, then slide the tube over your bit. It works like a commercial drill stop, it just doesn’t use a screw to secure it. I prefer to use brass tube but you can use heat shrink tubing, plastic tubing from a hobby shop, or even a drinking straw. You can even cut a slit into the drinking straw so you can pull it tighter, then secure it with tape, if you can’t find any tubing that fits the drill bit you need. Slide it onto your bit and drill. When the tube hits your workpiece and runs out of slack on the drill bit, it’ll stop you from drilling further.

A variant on this trick is to use a piece of wire and wrap it around the bit kind of like a spring. This works, but tubing is quicker and easier. It’s not hard to get into the habit of keeping a drinking straw in your toolbox.

Improvise with tape

Last and least, you can put a piece of tape on your drill bit at the depth you want. Rather than wrapping the tape around the bit to try to make a stop out of it, it’s usually more effective if you tape it over the bit, like a flag. The tape won’t do a great job of stopping the drill but when it hits, you’ll see the flag clear the sawdust or shavings off your surface, especially if you’re drilling wood. Work slowly and watch carefully, and this method can work for you.

I definitely prefer the other methods, but in a pinch, tape definitely works when you want to make sure you don’t drill too deep. I’ve used it more than once.

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