Cutting granite countertops questions

More on the granite fab project.  I got the main bar complete.  In the process of cutting, I realized an issue.  I made two cuts, both of which were awful.  I was using a Dewalt non-segmented diamond blade and it sucked.  Here was the process

- chucked up a 7" Dewalt non-segmented diamond blade in my worm-drive circ saw
- filled a couple 2-liter coke bottles with water and drilled a 1/8" hole in the lid for irrigation and had a friend irrigate continuously.
- clamped a straightedge to the the granite at the appropriate spot.
- laid some 2" masking tape on the granite to prevent chips (although it wasn't an issue)

The first cut, the straight edge was to the left of the saw.  I got about 8" in to a 34" cut and it got really hard to push.  I lifted the saw out of the kerf and realized that the blade kerf had curved to the left by about 1/2" and was binding.  So I reset the straight edge for the opposite direction and started from the other side.  That cut, no matter what I did, it curved away from the straightedge. (still going left)  So I went to HD and got a "better" Irwin blade.  I decided to set the depth at 1/8", then about 1/2", then full depth.  I finished that cut relatively straight, but it still "walked" a bit in both directions.  Fortunately that cut goes against a wall so I don't care, but the remaining pieces need to be re-squared and trimmed before I polish and install.

Tips on cutting granite?  Am I using the wrong blade?  I don't want to keep trying expensive blades and keep messing up my rocks.

If I'm free handing a cut at work I use a 7" angle grinder.  We have a small circular saw we use to put rods in but it's only a 3" blade, has water and we only go 1/4" in with that. 

Take your time and go slow. It's easy to keep a straight line with an angle grinder. The tough part is keeping it square. Err on the side of leaning it in towards the top of the piece and you can square it up with a cup wheel prior to polishing.

Edit to add with 2CM a 4.5" blade would be plenty.

And watch that dust, all kinds of silica and bad stuff in there.

Is hiring a plunger saw and guide an option?

Like one of these?

I've used them for cutting aerated concrete panels as well a fiber cement  sheeting and they do a great job with those.

Not sure a plunge would help in this case... at least with the blades I used.  They had a mind of their own.  I think my blade on a plunge would have still bound up.  A plunge would have at least let me set several depths and gone slowly with a little more ease.

Is there a style or type of blade that works better than a non-segmented tile blade?

We use blades similar to this on our angle grinders. We use them dry. 

Personally, I wouldn't use a circular saw. I've never had any luck even cutting something soft like concrete and keeping a straight line with one. 

I would avoid any and all blades from the big box stores. If there is some type of builders supply store around, they will have a much higher quality blade available. 

LOTS of water and go SLOW!!! 

Not sure if it would be able to wander if you're using the guide. Even if it started to, you'd set it up so the guide is on the good side of the cut, with the waste to the outside. That way it can't wander into the good material and if it tries to wander outwards, you can pull back and take another bite. 

I did a bunch of 30mm lime stone pavers a couple of months ago with a 9" continuous blade on a tile saw and was able to take slivers off. Granted limestone isn't as hard, but the fact that the saw couldnt wander meant I got great cuts, no binding.

I don't know much about this, but are you trying to cut all the way through in one pass?  Could you set the depth of the saw at a quarter inch, then make a pass at a half inch and so on until you are all the way through?  It might keep the blade cooler.

Doesn't seem to matter if I cut 1/4" at a time or try to cut the whole way at once.

When I put my clamped guide on the left of the saw and cut just about 1/4", it binds.  The blade pulls/bends left and squishes the saw against the guide.  If I stop and lift the saw straight up, the blade twangs to the right.  The blade itself is going crooked, not the saw.  I was hoping it was just a defective blade, but the new blade did the same thing... only it did it both ways.

I got a quote for $350 for a granite fab place to do it.  I think I'll pass on that option.

I'll try an angle grinder and see what happens.

I prefer to start the cut with the blade spinning away from me. Let it drop through the material and slowly pull it towards me. Get a feel for the speed that the blade wants to cut at and just guide it and let it eat. With my left hand on the head of the grinder and my right on the handle holding the switch on and my pinky dragging the in the piece. 

If you have a practice piece to use to get a feel I think you'll agree it's easy to hold a straight line.

A blade walking like that usually means one side of the blade is more worn than the other (or kerf, if it’s a wood blade)

Since you are using a rigged water setup, is it possible you are wetting one side more than the other?  If you were to overheat one side, you’d kill the blade rapidly, and it would cut in circles. 

In reply to Nick Comstock :

Just out of curiosity, what do you do to control the dust and silica inhalation if you are cutting dry?

Side note...

All diamond blades are not alike. Some will cut concrete but not granite. 

The blades we typically use on commercial sites are a lot bigger than 7”, but they can cost nearly $600 each. If your “expensive” blades are $30, then they could be the problem. 

Nick is a pro at this. 

In reply to SVreX :

In the shop we have a big dust collector that has a hood that we push the piece under for dry grinding and cutting, plus respirators. But 99% of all cutting is done wet, or on the water jet. 

We do all fabrication in the shop so that hopefully nothing ever needs to be done at the job site. Very occasionally a builder or remodeler will make a change after the job is templated and if it's minor we'll address it on site. Usually take the piece outside or in the trailer and cut/grind whatever is needed. But big changes come back to the shop to get cut on the water jet. 

When we cut out drop in sinks or cooktops at the job we have a guy with a shop vac holding it right behind the grinder that does a surprisingly decent job of catching most of it. 

I did have to cut 1/4" off of the bottom of some splash at a job site . A 110" long piece and two side splashes.

Just cut it a little heavy and clean it up with the cup wheel in the grinder. Don't cut tight to your finished dimension.

SVreX said:

A blade walking like that usually means one side of the blade is more worn than the other (or kerf, if it’s a wood blade)

Since you are using a rigged water setup, is it possible you are wetting one side more than the other?  If you were to overheat one side, you’d kill the blade rapidly, and it would cut in circles. 

I suddenly feel simultaneously vindicated and stupid.  Vindicated because I think we found our answer, and stupid because of what the answer is.  I think we favored one side.  We tried to hit from the back and squirt equally up the blade, but the worm drive being on the right side of the blade made it hard to get water in that side (without accidentally squirting water in the vents of the motor).  We ended up trying to shoot in from the front but it was most definitely biased toward the left side of the blade.

For all of my street smarts, this one just escaped me.

Nick Comstock said:

I prefer to start the cut with the blade spinning away from me. Let it drop through the material and slowly pull it towards me. Get a feel for the speed that the blade wants to cut at and just guide it and let it eat. With my left hand on the head of the grinder and my right on the handle holding the switch on and my pinky dragging the in the piece. 

If you have a practice piece to use to get a feel I think you'll agree it's easy to hold a straight line.

Drop through the whole way?  Or do you make several passes?

Do you find with the blade spinning away from you that it wants to pop up out of the kerf, or is there not the danger of that in such slow cutting?

I actually have my sink cutout from my kitchen remodel which I could hack up, but I'm not sure it will be apples to apples.  That cutout is 1.25" quartz and this granite project is 2cm rock.  But, I want to cut that sink scrap into two little end tables anyway, so practice is practice.

In reply to Curtis :

It’s possible your blade would have cut better dry (assuming it was a wet/dry blade). It would have heated both sides of the blade evenly. 

Nick’s description of 2 people using a shop vac and respirators is probably perfectly adequate. However, I can’t allow it on a commercial job site (it’s not in keeping with OSHA regs). I also can’t allow a water bottle like you described.  

The commercial dust free systems are very expensive. 

But for your personal use, it’s just smart to be careful. 

In reply to Curtis :

BTW, bravo for trying. Cutting wet is much safer than cutting dry. 

In reply to Curtis :

Yeah I go all the way through. I try to keep a finger in between the head of the grinder and the piece. It helps with control and the blade is not buried. I've never had a blade bind or want to jump. The key is to go slow add let the blade go at it's speed and just guide it. 

SVreX, I can't think of a commercial project that we've been on since I've been here that we've needed to cut anything on site. Everything is usually undermount which is all completed at the shop. My guess is that if we ran into an issue in a strictly controlled commercial job we would complete all the cuts at the shop then clamp bars to the piece to keep it whole during transport. 

In reply to SVreX :

In another industry we had Hilti dustless tools and man they were very expensive. 

SVreX said:

In reply to Curtis :

It’s possible your blade would have cut better dry (assuming it was a wet/dry blade). It would have heated both sides of the blade evenly. 

Nick’s description of 2 people using a shop vac and respirators is probably perfectly adequate. However, I can’t allow it on a commercial job site (it’s not in keeping with OSHA regs). I also can’t allow a water bottle like you described.  

The commercial dust free systems are very expensive. 

But for your personal use, it’s just smart to be careful. 

It was a wet blade.  Might try a dry or wet/dry next time.

We used respirators simply because even wet there are plenty of silicates being thrown in the air.  I don't think they're particularly wonderful respirators (the grey, dual-filter versions from HF), but I had them around from a latex wall painting project that involved a sprayer and I figured they were better than nothing.

Nick Comstock said:

In reply to Curtis :

Yeah I go all the way through. I try to keep a finger in between the head of the grinder and the piece. It helps with control and the blade is not buried.

SVreX, I can't think of a commercial project that we've been on since I've been here that we've needed to cut anything on site. Everything is usually undermount which is all completed at the shop. My guess is that if we ran into an issue in a strictly controlled commercial job we would complete all the cuts at the shop then clamp bars to the piece to keep it whole during transport. 

Makes sense.  Thank you both for your input.

When the guys came out to do my quartz countertops, the sink cutout was only in the corners (it would have been too fragile with a full cutout for transport).  The guys just chucked up a 7" diamond blade in a circ saw and finished the cut on site.  I was amazed at how easily they cut it out in 5 minutes.  Of course... that was quartz, not granite... and their blade probably cost $250... and they knew what they were doing.  I just had a false sense of confidence going into this project.  I mean, come on.... I'm a theater tech director.  I build things like remote-controlled vomit machines and PVC contraptions to make rain happen on stage.  I can cut granite!  (I just should have asked here first)

Nick Comstock said:

In reply to SVreX :

In another industry we had Hilti dustless tools and man they were very expensive. 

OSHA does not care how much they cost. 

Every job you do is commercial. You may be installing in residences, but your business is commercial. 

Residential and commercial work BOTH require meeting the OSHA standards. You’re  just less likely to get caught on a residential project. 

Thanks to your grinder/freehand recommendation, here is the completed bar.  The side tables fold down so we can store the whole thing in the closet in between shows.  Couldn't have done it without your help, guys.  Thanks.  I ended up with a 4.5" wet/dry Dewalt blade that I chucked up in a grinder and cut dry with it.  Then I used the old wasted blade on a slower speed chucked up to a polisher to recreate the bevel and polish up the edge.  I got it pretty nice with a final treatment of 80 grit on a belt sander, and then I dipped a rag into polyurethane and hit the edges.  Unless you actually touch it, you can't tell it isn't a factory edge.

Now I have one more full slab of 34" x 85" that I will cut in two lengthwise to make a shelf/rear table.  I think I'll cut it into 15" and 19" and do a counter-height cabinet with the 19" slab and a hutch with a shelf using the 15" slab and it will go against the steps beside the fridge.

The bar cabinet is made from Exotic Phillipine Mahogany (Meranti) which is a really fancy way of saying "Luan."    There is some birch and maple in the trim work, but believe it or not, that thing is mostly Luan.

Only other thing I want to do to the bar is put some trim on the edges of the plywood that is under the fold-up wings since it is visible from some angles.

P.S.  My shop is a dusty berkeleying mess.