How do I use a circular saw safely?

A circular saw is fast, accurate with a guide, and the least forgiving tool most households own. Nearly everything about using one safely comes from one mechanism — kickback — and understanding it makes the rest of the rules obvious rather than arbitrary.

Safety

Step by step

1. Understand kickback before anything else.If the cut closes and pinches the blade, the spinning blade grabs the material and drives the saw backwards at speed. It happens in a fraction of a second. Every support and stance rule below exists to prevent it.
2. Support the work so the cut opens.Support on both sides of the cut with the offcut free to drop, or support the whole sheet on foam or battens and cut through into them. Never bridge a piece between two supports and cut in the middle — that closes on the blade.
3. Set the blade depth correctly.About one tooth's depth beyond the underside of the material. Deeper exposes more blade, increases kickback force and is more dangerous, and it does not cut any better.
4. Check the lower guard moves freely.It should spring back over the blade the moment the saw leaves the cut. Never wedge it open, and clear any sawdust that stops it retracting. A guard held open is how the worst injuries happen.
5. Stand out of the line of the saw.To one side rather than directly behind it, so if it does kick back it travels past you rather than into you. This one habit changes the outcome of the accident this tool has.
6. Clamp the work and use both hands.Never hold the workpiece with one hand and the saw with the other. Both hands on the saw, work clamped or supported by weight.
7. Use a guide for a straight cut.A straight batten clamped parallel to the line, offset by the distance from the blade to the edge of the base plate. Measure that offset once and write it on the saw. Freehand cuts wander and binding follows.
8. Let the blade reach full speed first.Start the saw with the blade clear of the material, let it come up to speed, then feed it in. Starting in contact is a common cause of kickback.
9. Feed steadily and do not force it.A steady rate with the saw doing the work. Forcing it slows the blade, heats it and increases the chance of binding. If it is labouring, the blade is blunt or the depth is wrong.
10. Never back the saw out of a running cut.Release the trigger, wait for the blade to stop completely, then lift it out. Withdrawing a spinning blade is a reliable way to cause kickback.
11. Cut with the good face down.The blade cuts upwards through the material, so tear-out is on the top face. Mark and cut with the finished face downwards, and score the line first for a very clean edge.
12. Choose the blade for the material.Fewer teeth for fast rough cuts in timber, many teeth for a clean cut in sheet material and laminate. A blunt or wrong blade is behind most burning, wandering and binding.
13. Wear eye and ear protection.Both, every time. A circular saw is loud enough to cause cumulative damage and throws debris directly forward.

Tips

• A sheet of rigid foam insulation on the floor is the best sheet-cutting support there is. Set the depth just past the board and cut into the foam — the sheet is supported everywhere and cannot pinch.
• Measure the base-plate offset once, write it on the saw in marker, and every guided cut afterwards is accurate first time.
• If you cut sheet material regularly, a track saw removes both the guide setup and most of the kickback risk. It is worth the difference.

Common mistakes

• Supporting a board at both ends and cutting in the middle — The two halves sag and close on the blade, which pinches it and causes kickback. Support so the offcut can fall free, or support the whole sheet from underneath.
• Setting the blade far deeper than the material — It exposes more blade, increases the force of any kickback, and makes no difference to the cut quality. A tooth's depth beyond is right.

If it doesn't work

Questions people ask