CIRCULAR SAW BLADE – HOW TO SAFELY CHANGE ONE

In this post I take you through the principles of changing a circular saw blade. As you might imagine, I put an emphasis on safety.

Here’s a Youtube video of Ethan’s that demonstrates a blade change:

FIRST, UNPLUG IT!!!

Treat your circular saw as you would a weapon. Make sure it’s not loaded, so there’s no way it can harm you. Electricity is your saw’s ammo. Always be sure to unplug your saw before changing the blade. Or even touching the blade! When I’m changing blades, I always throw the saw’s cord onto my work surface so I can see the plug.

To the old hands out there, that may seem excessively cautious. But the idea is to form safe habits early. Then always be conscious of safety.

WHEN SHOULD I CHANGE MY CIRCULAR SAW BLADE?

The best way to recognize a dull blade is by sound and feel, not sight. The paint and/or printing on your blade gets scuffed long before the blade is dull. Therefore, just looking at the blade doesn’t tell you much.

So, when your blade is new, make a couple of cuts. Consciously note the sound of the blade cutting through the wood. Also, note how little pressure is needed to push the saw through your material. Later, your saw may sound like it’s laboring. Or you feel like you have to push harder to complete a cut. If either of these things happens, replace your blade.

WHAT KIND OF CIRCULAR SAW BLADE SHOULD I USE?

Understandably, this depends upon what you are going to be cutting. (I only address wood-cutting blades in this post).

Are you cutting framing lumber, deck lumber, OSB, or plywood? If so, you’ll want a blade with fewer, larger teeth. Generally, for a 7 1/4″ blade, that’s 24 teeth.

Note: your circular saw blades should always have carbide teeth. Carbide teeth are harder, so your blade stays sharp longer. Also, carbide teeth are thicker than the body of the blade. That means that your “kerf”, or width of the cut itself, is wide. This helps to keep your blade from binding, thereby reducing kickback.

Here’s a video of Ethan’s that explains kerf. It’s an important concept to understand.

For trim work or cutting cabinet-grade plywood, you want more, smaller teeth. This reduces tearout of your material. A minimum of 40 teeth. Generally, I use 60-tooth blades for fine cutting.

NOTES:

1. When you buy blades, make sure you are getting the right diameter and arbor size for your saw. For my Makita, that’s 7 1/4″ diameter, 5/8″ arbor.
2. If you are cutting with a blade that does not have carbide teeth, be extra careful to avoid kickback.
3. You can’t go wrong buying Diablo blades.

FINALLY, THE STEPS TO REPLACE A CIRCULAR SAW BLADE

1. You unplugged your saw, right? Also, use gloves. Those teeth are sharp!
2. Locate the wrench that came with your saw. If you can’t find it, use a box end or open end wrench of the appropriate size. The size for a 7 1/4″ Makita saw is 13mm. As a last resort use an adjustable “Crescent” wrench.
3. Set your saw on a wood surface–one that you don’t mind tooth marks on.
4. Rotate your blade guard out of the way, to allow the blade’s teeth to dig into the wood surface a bit.
5. All modern circular saws have a spindle lock. This is to keep your blade from turning as you are loosening your bolt. Generally it’s located at the back of the saw, between the upper blade guard and the motor. Press the spindle lock in and hold it there. Rotate your blade (hence the gloves) until you feel the spindle lock engage. Continue holding the engaged lock. Note: if you let go of the lock, it will pop back out and you’ll have to repeat the process.
6. 
7. While the spindle lock is engaged, use your wrench to turn the bolt counter-clockwise (anti-clockwise for you readers who speak proper English).
8. Remove the bolt and the heavy washer.
9. With the blade guard retracted, remove the old blade.
10. Put the new blade onto the saw. Be sure that the teeth of the blade are pointing up at the front.
11. Put the washer back on. The washer probably has flat spots to engage with the arbor. Rotate the washer until you feel it drop down to engage with the arbor.
12. Insert the bolt and finger-tighten it, turning clockwise.
13. With the spindle lock engaged, tighten the bolt. You don’t need to go overboard with the tightening. That’s because the spinning of the motor acts to tighten the blade.
14. Wiggle the blade to make sure it’s tight.
15. Return your blade wrench to wherever it belongs.
16. Plug the saw back in. You’re ready to cut!

THAT’S IT!

Here’s a post with a tip to keep your circular saw in good shape:

Thanks for reading. I’m Ross James with The Honest Carpenter. If you have a question for me, or if you have a suggestion for a subject of a future blogpost, please go to our Contact page.