Circular saws and blades

[Greg R]

I'm looking for some guidelines in selecting a circular saw for cutting 3 cm granite.  I've came across the following calculation for surface feet per minute (SFPM):

SFPM = Pi x RPM x Blade Dia.
or
Blade Dia. = SFPM/(Pi x RPM)

With a SFPM range of 4,500 to 6,500 for granite, I figure that a 4" to 6" blade is needed if a 4,300 RPM saw is used.  Of course, the variables would be saw RPMs and blade diameter.

For doing small jobs, a 7-1/4" wormdrive Skil saw should work fine, right?

Also, how about diamond blades vs. carbide tip blades?  And hypoid drive saws vs. worm drive?

Thanks,
Greg

[Mark D.]

Most people buy a 7" turbo blade suitable for cutting granite and run it on a 7 - 7 1/4" circular saw. I have experience with both the worm drive and the hypoid saw and they both work well. Make sure you are cutting backwards as the blade spins from the bottom up through the front of the saw. By cutting backwards you will not chip the already polished surface as you will be cutting into the stone instead of cutting out of the stone.

Carbide blades will NOT cut granite - they will first chip the stone and then they will overheat and disintegrate. Here are a couple of options for high quality dry cutting blades suitable for cutting granite slab with a Skilsaw:
http://www.defusco.com/supreme-granite-turbo-blade-p-1821.html
http://www.defusco.com/disco-blue-stone-turbo-blade-p-2107.html

I hope this helps.

Mark

[LOL]

Howdy,
I'm new around here and have been getting set up to do some small scale fabrication. I have noted the instruction to saw granite with a circular saw by dragging it backwards. Why not simply layout and cut the slab from the bottom? Obviously this means another rotation of the slab but that seems easier to me than the akward dragging of the saw. Plywood and laminate are often/usually cut this way.

Cheers,
Larry

[Mark D.]

Wouldn't you rather see what you are doing? It makes it easier to correct a small error before it becomes a big error. If your diamond blade loses tension your blade could wander, and if it is on the top corner it would be more visible than the bottom edge once the counter is in place.

The #1 reason for not flipping the slab over and pushing the saw is that the blade will still be passing from the back of the slab and out the front (the backside revolution is doing that), and if it hits the edge of some crystal in the granite it will STILL make a chip!

Trust me on this, pull the saw backwards and enjoy a cleaner cut!

Mark