Circular Saw blade size? How important?

[pboreham]

I've just brought a circular saw to start my cutting and it comes with a 24 tooth blade.

I have been recommended to get around a 40 tooth blade, which is fine, there were loads in B&Q today.

BUT, the blade that my saw came with is 185mm and the ones in the store are 184mm - couldnt see any 185's.

The instructions point that only 185mm blades should be used - is this correct, or will a 184 work ok?

Thanks!

[bfauska]

As long as the blades have the same type/size hole in the middle to attach to the saw, a 1mm difference shouldn't be a problem, especially if the blade is smaller than what the manual specifies.  A bigger blade I might hesitate to use, but the only thing that would be a problem with a smaller one is that your cutting capacity will be decreased (you won't be able to cut wood that is as thick) but the difference in capacity will only be .5mm.

Of course if somehow the saw explodes and you get seriously wounded I feel obligated to tell you that my statement above is only an opinion, and while I use tools nearly every day at work I AM NOT THE MANUFACTURER OF YOUR SAW.

I bet you'll be fine, have fun, and good luck.

[ChadTower]

That may have to be factored into his depth calculations, though, depending on the saw.

[DrewKaree]

As long as the arbor hole is the same, you'll be fine.  Have at it.

[shardian]

that 1mm is probably just the difference between the OEM blade and aftermarket blades - either way, definitely nothing to worry about. The "don't use different blade diameter" thing is to keep you from throwing a 12" blade onto a 10" saw, and other situations like that.

[pboreham]

Thanks for all your help guys!

I ended up erring on the side of caution and found a blade to fit. Amazingly, I couldnt find anywhere near where I live with a 185mm blade - they were all 184mm.

I was about to give up, but the last shop finally had a 185mm, but with a 30mm bore!!! (I needed 20mm). Again, luckily, this one came with a 20mm bore adapter and though a bit nervous about using it, it worked out fine and was a great tool!

[ChadTower]

It's not the blade, it's the motion.

[bfauska]

It's not the blade, it's the motion.

Yep, mines about 1mm undersized  and I've never had any complaints.   

[tba]

the only thing is smaller blades spin faster (higher RPM) make sure you aren't going out of spec for your saw, but 1mm pfffft, that's barely a measurement! i wouldn't have worried about it!

[bfauska]

The motor spins at whatever speed the motor is meant to spin at... big blade, little blade, no blade.  Some saw blades are rated to spin at different speeds than others, but as long as the blade can spin at least as fast as the motor is going to turn it then you are fine.

As far as size of blade to speed comparisons RPM=RPM
If the confusion is about the speed at the outside edge of a blade, then it would be correct to say a larger blade is going faster, Big blade=long circumference=more feet per second of linear travel.  If we were talking about cars however it could sound different but be the same essential thing.  With little tires you need to have more RPMs to go the same speed as a car with bigger tires.

[tba]

RPM speed of saw blades are measured on the outer circumference. so smaller blade = faster RPM. you are right i did say make sure your saw isn't out of spec, i meant blade.... the motor spins the same speed all the time, but the blades are only designed to spin at a certain speed without failure. don't quote me on this but, i believe, they are usually 10,000 rpm which is usually out of the range of most circular saws, unless you did something really foolish and put a 6" blade on a 12" saw, or something crazy like that.

[patrickl]

RPM is a rotational speed. It has nothing to do with the diameter.