You finish drilling a whole, flip the piece over, and the back looks something like this:
We’ve all been there. But luckily, there’s an easy way to prevent it.
The best way to prevent drill blowout is by clamping a scrap piece of wood to the backside of the piece you’re drilling on. Then when you drill the whole, the wood that would’ve otherwise “blown out” hits the scrap wood and remains in place.
But if that won’t work for your project, there are a couple of other great methods too, so lets dive in.
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What is Drill Tearout?
Drill “tearout” or “blowout” is when chucks of wood on the backside of a hole chip off when the hole is drilled. This is really common when drilling with softwoods, but isn’t unheard of when drilling holes in hardwoods either.
To be dead honest, if I’m working with softwoods or plywood and don’t go through special effort to prevent tearout, it happens. I could make a collage.
(This is my TV Lift Cabinet. Other than this little mistake, it’s actually great.)
Blowout is also much more likely when you’re using a spade bit versus other types of bits. I actually don’t remember the physics behind this, but my engineer father told me it was true, so I’m going to trust him.
The Best Way to Prevent Drill Blowout
Step 1: Clamp Scrap Wood to the Back of the Piece
Start by clamping a piece of scrap wood to the back of the piece.
If you’re drilling a hole before assembly, this should be easy to do. If not, and you’re unable to figure out a way to clamp the wood, don’t worry, I’ve got another method that works too!
Step 2: Drill Hole Normally
Drill the hole the exact way you usually do. That’s it. Really. No blowout.
You will probably sacrifice the scrap wood a bit in the method – I never know when to stop drilling, so I usually drill into the scrap wood at least a little.
But that’s okay, right? It’s scrap wood. That’s what it’s there for.
Method Two: Preventing Blowout by Drilling From the Other Side
So for whatever reason, you’re unable to clamp a piece of wood to your piece. Or maybe you tried the first method, and somehow still got blowout. That’s okay. There’s another way.
Instead of using a twist drill bit, grab a brad point bit or a spade bit (for bigger holes.)
Brad point bits and spade bits have pointy ends that drill through the wood before the rest of the bit. That makes them really awesome for this method.
(It’s also worth noting that brad point bits in general are good for reducing blowout. But combining it with this method gets you double the protection!)
Step 1: Estimate the Depth of the Wood
Place your drill bit next to the wood, and estimate when the drill bit with hit the other side.
Mark this place on the drill bit with a piece of masking tape. This will give you an idea of when you’re getting close to the end when you’re drilling your hole.
Step 2: Drill the Hole Slowly
Drill slowly, checking every so often that you haven’t drilled through all of the wood.
Step 3: Stop Drilling When the Point Pokes Through
As soon as the pointy bit on either your brad point bit or spade bit pokes through the wood, stop drilling.
Step 4: Drill From the Other Side
Flip the board over, and finish drilling the hole from the other side.
The small hole you made is a perfect guide, showing you exactly where to drill the hole.
There won’t be any tearout with this method, because the drill bit never tears through an unbroken side of the wood!
Method 3: Drilling a Pilot Hole
Frankly, method 3 is better than method 2. But honestly? I’ve always done method two, and didn’t even consider method 3 until my dad mentioned it. I feel a little silly.
Method 3 is basically the same as method 2, except instead of drilling slowly and repeatedly checking to make sure you didn’t accidently drill all the way through, you start by drilling a smaller pilot hole.
Then drill your main hole, only drilling 3/4″ through the wood.
At that point, flip the board over, and finish drilling the hole.
Like I said, easier. But I never thought of it (or tried it) until I was writing the post. Clearly, I was missing out.
Method 4: Choose a Better Bit
I don’t love this method as much, because it doesn’t necessarily eliminate tearout, just reduces it. But if you’re working on a project where the blowout can’t be seen, and you don’t want to spend the extra time drilling pilot holes or clamping scrap, this is probably the way to go.
Brad point bits have really sharp outer edges that score the outline of the bit before punching through. This significantly reduces blowout compared to a normal twist bit.
Similarly for larger holes, Forstner bits do a much better job reducing blowout than spade bits. They make super clean holes, although they’re usually used with drill presses.
It’s not impossible to use a Forstner bit with a normal drill, but the steadiness of the drill press helps a lot for creating a clean hole.
Blowout on the Front
Tearout is usually something that happens on the back of the piece, but if you happen to be experiencing it on the front, there’s an easy fix.
Simply put a piece of masking tape down before you drill, and mark the spot to drill on the masking tape instead of the wood.
Then when you drill, the bit will tear up the masking tape instead of the wood.