Nothing is more frustrating than spending £50 on oak skirting boards only to find your “perfect” 45-degree mitre doesn’t close properly. You check the saw, the dial says 45°, but the gap in the corner says otherwise.
In my 50 years of DIY, I’ve learned one hard truth: You cannot trust a mitre saw straight out of the box. Whether it’s a budget Parkside or a top-tier DeWalt, “factory calibrated” usually means “close enough for a rough shed build,” but not for fine trim work.
If your joints aren’t lining up, it’s rarely the tool’s fault, it is actually the setup. In this guide, I’m going to show you the exact steps I use in my own garage to take a saw from “98% okay” to “dead-on accurate.”
Expert Verdict: “In my 50 years, I’ve never met a saw that was 100% perfect straight out of the box. Even a £600 DeWalt can get knocked out of ‘true’ during shipping or by a heavy-handed delivery driver. If your skirting joints have gaps, don’t blame your skills, instead blame your calibration. Here is how to ‘zero’ your saw like a pro.”
How I Wrote This Guide
- The Source: 50 years of making mistakes so you don’t have to.
- The Method: I have calibrated everything from old school manual saws to my current DeWalt sliders.
- The Goal: To show you how to get professional results in a standard UK garage or shed, without buying expensive laser alignment tools.
1. The “Frustration Checklist”: Why isn’t it cutting square?
Before we start turning bolts, check these “quick fixes” that catch out even the veterans:
- The Sawdust Trap: A tiny pinch of sawdust trapped between your timber and the fence will throw your cut off by half a degree. That doesn’t sound like much, but on a wide piece of skirting, it’s a 2mm gap.
- The “Head Push”: Beginners often accidentally push the saw handle to the left or right as they pull down. Let the tool do the work; keep your pressure purely vertical.
- The “Spring Back”: If you release the trigger and let the saw fly back up while the blade is still spinning, it can catch the wood and “chew” the edge, making the joint look wonky. Wait for the blade to stop before lifting.
2. The “Five-Cut Test”: How to find the “Invisible Error”
If you use a standard plastic square, you might think your saw is square. But a tiny error of 0.1° is almost invisible on a square and yet it will ruin a picture frame. The Five Cut Test magnifies that error by 4 times so you can see it.
You will need: A scrap square piece of MDF or Plywood (roughly 12″ x 12″).
- Cut 1: Place your scrap against the fence and trim about 1cm off the right-hand side. Mark this edge as #1.
- Cut 2: Rotate the board clockwise so edge #1 is now against the fence. Trim the next side.
- Cut 3: Rotate again. Edge #2 against the fence. Trim.
- Cut 4: Rotate again. Edge #3 against the fence. Trim.
- Cut 5 (The Truth): Rotate one last time. Now, instead of a trim, cut a thin “sliver” (about 1cm wide) all the way through.
The Result: Look at that sliver. Use a ruler or callipers to measure the top and the bottom.
If the sliver is the same width at both ends: Your saw is perfect.
If one end is wider: Your saw is out of square.
Because you rotated the board 4 times, that tiny error has been multiplied. If the bottom is 2mm wider than the top, your saw is actually out of square by only 0.5mm, but now you can actually see it to fix it!
3. How to Calibrate (The “Enda” Method)
Don’t just start twisting every screw you see. Most mitre saws are adjusted in this specific order:
Step 1: Square the Fence to the Blade
Unplug the saw. Lower the blade and lock it down. Place a Machinist Square or a reliable Speed Square against the flat part of the blade (avoid the teeth!). If there’s a gap, loosen the bolts holding the fence and tap it gently with a rubber mallet until it’s flush. Tighten it back up.
Step 2: Reset the “Zero” Pointer
Once the fence is physically square, look at your mitre scale. If the little red pointer isn’t exactly on “0”, loosen its tiny screw, move the pointer to zero, and tighten it.
Enda’s Veteran Tip: “Never trust the factory pointer. Trust the metal. Always square the fence to the blade first, then move the pointer to match the truth.“
Step 3: The 45-Degree Bevel
Tilt your saw to the 45-degree stop. Use a square to check it. Most saws have a “stop bolt” at the back. If your cut is 46° instead of 45°, you simply turn that bolt in or out until the head stops at the perfect angle.
“Now that your saw is square, make sure you’re using the right blade. See my guide on [How to Choose a Mitre Saw Blade for Clean Cuts].
Where Is Your Mitre Saw Going To Be Placed?
This is really your first decision and it is an important one to make. Ideally you will have somewhere permanent that you are going to put the saw, and be able to bolt it down. That is of course if you want to make it a permanent feature in your shed, garage or workshop.
Perhaps you have got a saw stand, and if so, then you will be able to clamp your saw on there, and it will then be able to be taken on and off at will. For most people though, they will just want to set it up, use it and then store it away. For those people, they will want some form of temporary solution such as clamping it into something like a Workmate.
“Struggling with the math? Check out my [Cheat Sheet for Cutting Skirting Board Mitres].
Why “Out of the Box” Isn’t Good Enough
Most manufacturers ship saws with a slight margin of error. A 1 degree error might not look like much on a single cut, but when you’re joining two pieces for a corner, that error doubles to 2 degrees.
That’s the difference between a seamless joint and a gap you have to fill with caulk.
Step 1: The “Physical” Check (Before You Power Up)
Before we look at the dial, we need to check the hardware. Over years of use, or a bumpy ride in a delivery van, the Fence (the back rail) can move.
Enda’s Pro Tip: Take your most trusted Try Square. Unplug the saw. Lower the blade and hold the square against the flat body of the blade (avoiding the teeth). If you can see light between the square and the fence, your saw isn’t square. It doesn’t matter what the dial says; if the fence is out, the cut is out.
Your saw needs to be cutting square, and that is the really important thing.
In the video, this chap shows you how to ensure that your saw is set up accurately. He begins using his table saw, but does move on to checking the mitre saw, so just bear with the initial part of the video.
Squaring The Fence on a Mitre Saw
The fence as you may know is the part on the saw against which you push the piece of wood against to make your cut. Have a look at the video below for clarification. The blade makes a vertical cut, and it is really important that this is set on a cross cut to exactly 90 degrees. When you buy your saw this will usually be the case, but it does no harm to check this with a square.
As long as the saw is then set up on a completely level surface, then you will get a very accurate cut. Here is a video on how to go about doing just that.
Accuracy Using A Mitre Saw Stand
The same applies to setting up your saw onto a stand. What is vitally important here is that the actual stand has been set up on a level surface and adjusted. If the stand is sitting on any type of incline or slope, then you will also get an inaccurate cut.
The best way to do that is to set it up on a level surface, and then use a long spirit level, to check how level it actually is. You may need to place something that will act as a wedge under a particular leg or legs to get the perfect horizontal level
Mitre Saw Accuracy FAQ
Why won’t my 45-degree mitre joints close properly?
This is the most common frustration. If your angles are even 0.5° off, the error doubles to 1° when you join two pieces together. Usually, this happens because the saw’s detent (the “click” into the 45° slot) is slightly misaligned or there is sawdust trapped in the mechanism. Always vacuum the base before making precision cuts.
Are sliding mitre saws less accurate than “chop saws?”
Generally, yes they are. A sliding saw has more moving parts (the rails), so there is a higher chance of “play” or wobble. If you are doing basic framing or decking, a slider is fine. If you are building fine furniture or picture frames, a non-sliding “chop” saw is often more rigid and accurate out of the box.
How do I fix a mitre saw that is cutting “wonky” on the bevel?
If your vertical cuts are square but your bevel (tilted) cuts are off, check your blade. Thin-kerf blades (the skinny ones) often “deflect” or bend slightly when cutting at an angle, especially through hard timber like oak. Try slowing down your cut and let the blade do the work, and never force it down.
My wall isn’t square—should I still trust my saw?
In the UK, especially in older houses, walls are rarely a perfect 90 degrees. If you cut a perfect 45° for a 91° corner, you’ll have a gap. Enda’s Trick: Use an angle finder (or a cheap plastic protractor) to measure the actual corner, then divide that by two for your saw setting.
Can I use a mitre saw to cut a “straight” line?
You can make a “cross-cut” (cutting across the width of a board), but a mitre saw cannot “rip” a board (cutting down the length). For long straight cuts, you’ll need a Circular Saw or a Table Saw.