tilesaw-patternbarcutIt’s all in the way you slice it. And the way you slice it is, apparently, profoundly affected by a good blade.

Check any glassmaker’s forum and you’ll find someone whose tile saw cuts glass about as well as a wood chipper. They run a pattern bar through the thing and instead of slices, they get frit.

This post is about how to fix that.

Not that I have any special expertise at using tile saws, mind you. What I DO have is a cheap, very badly made and out-of-true Chinese tile saw I got on eBay many years ago. Figuring out how to make it give me the cuts I need has taught me a lot.

I bought that saw because I needed to tile the bathroom in my new home FAST (who puts white carpet under a TOILET?), before my furniture arrived. I’d just spent all my money on that house, so a cheap eBay saw looked like the best deal around.

My brother-in-law (the construction manager and godsend SWAT team tile guy) gave it a dubious look. “THAT,” he said, “Is the crappiest saw I’ve ever seen. It’ll never last.”

sliced glass from a tile saw

Shown from top to bottom:
2mm sheet glass (for reference)
3mm sheet glass (for reference)
Pattern bar slices ranging from 1.5mm thick (5th from bottom) to about 4mm and roughly 8 inches long x 1 inch wide.

So that was back in 2003 (hah, Jerald!), and that stupid saw is still going strong. It ain’t fancy, and I wish I could get a saw that actually had fun stuff like a working water pump, but this thing won’t quit.

It makes remarkably fine cuts in glass sheet, sculpture, and pattern bar…such as the pattern bar slices shown at the right. These were taken from murrini cane bars and range from about 1.5mm thick (about like a dime) to around 4mm thick.

I make these cuts pretty consistently with this saw, have been doing this for years. So…must be doing SOMEthing right…right?

This is probably going to be boring (and redundant) for most glassworkers, but I thought I’d get all my saw work info down in a single post.

I am NOT pretending to be an expert in shop equipment terminology (as you can see by the updates/comments in the three years since it was originally written), or the last word in how to coldwork.

There are already some excellent tutorials and videos on using tile saws to cut glass, so it’s not really about how YOU should do it. If you’re not sure of the basics, I STRONGLY urge you to buy Johnathan Schmuck‘s (he has changed his name, BTW, to Johnathan Turner) very good book on coldworking.

You can also find a number of really great online tutorials on cutting with tilesaws, maintaining your saw and similar subjects. (Check out, for example, the excellent series on the HIS Glassworks YouTube channel).

I’ve studied those references, taken classes, and made many dumb mista…, er LEARNING EXPERIENCES, on my own. Somewhere along the road I developed The Glass Saw Manifesto:

Caveat–this works for me. YOUR mileage may vary. And like most good manifestos, this will continue to evolve so please help out by adding MORE comments and suggestions.

tilesaw-cheap

Cheap eBay tilesaw from 2003, $100 including stand and three diamond blades. Great deal but BOY, is this a lousy saw. And it will never, ever break. Darn it.

1. The most important part of my tilesaw is the blade.

My el cheapo tilesaw came with three diamond blades (what a deal, eh?). I was happy to get them, they’re great for making rough cuts for later coldworking. They’re also not bad for cutting ceramic tile.

But they are 2mm thick (about .085 inches) and my goodness they take a HUGE kerf out of the glass. (the kerf is the material removed by the blade–it’s the width of the blade plus whatever wobble widens it slightly.

I measured those cuts, and I’m losing around 3mm PER SLICE. That means that with every pass of the saw,  I’m losing the thickness of 1 sheet of glass.

big saw kerf in a ceramic tile diamond blade

My old blade cuts a kerf of about 1/8 inch (3mm, above) and the new one is about half that. Make a dozen cuts with the old blade and you waste 3/4 inch of glass!

²

Worse, if I’m very very careful, that blade will slice the glass to about 3/8 inch thick with a moderate amount of chipping and breaking. No amount of slowing down or skill that I’ve tried so far will make a finer cut.

I complained about that to expert coldworker Marty Kremer. His solution? “Buy a decent blade.”

On his recommendation I chose a 10-inch Result blade from HIS. It’s only half the thickness of those old blades–0.04 inches or a little more than 1mm thick.

This makes a huge difference in the quality of my cuts. I have much less chipout (the chunks that fly off the edges of the cut). And my saw kerfs are less than half the previous size,  so (as long as I’m making the same number of cuts–more about that in a minute) I’m wasting half the glass I used to.

The best part: Thin slices

Now I can slice a 2-inch thick block of glass, 10 inches long, into 1-2mm thick slices, thinner than a US dime. That means I’m able to cut thinner veneers from my precious pattern bar, getting more coverage from what’s probably a one-of-a-kind pattern.

Notice, however, that I did automatically add “and wasting less glass.” In fact, the thinner you cut, the MORE glass you can waste. If both my blades cut the same number of slices, the thinner blade wastes much less glass. But if I push my good blade to the limit, make as many cuts as I can…well, here’s what happens:

A blade that can slice thin, fine veneers of your pattern bar will allow you to maximize surface coverage. But the more cuts you make, the more glass you waste.

A blade that can slice thin, fine veneers of your pattern bar will allow you to maximize surface coverage. But the more cuts you make, the more glass you waste.

In the diagram, I’m slicing a pattern bar that’s 100mm long, 100mm wide, and 20mm high (about 4″ x 4″ x 2″) and my goal is to cover as much surface area of a flat sheet as possible. Let’s do the math:

Volume: 100 x 100 x 20 = 200,000 mm³ or 200 cm³
Blade 1: Minimum 9mm cut, 3mm kerf (so it’ll take 11mm per slice)
Blade 2: 1.5-2mm cut, 1.5mm kerf (we’ll say it’ll take 3.5mm per slice since not all slices will be as thin as 1.5mm)

Blade 1 (the old, thick blade)

  • Yield: 9 slices 100mm x 20mm x 9mm thick
  • Coverage: 180 cm²  (a bit less than 5 x 6 inches)
  • Stacked volume of slices: 162 cm³
  • Waste: 200 – 162 = 38 cm³

Blade 2 (the Result blade)

  • Yield: 28 slices 100mm x 20mm x 2mm thick
  • Coverage: 560 cm² (about 9 x 9 inches, or more than 3 times as much)
  • Stacked volume of slices: 112 cm³
  • Waste: 200 – 112 = 88 cm³

See how all those kerfs add up? I get triple the surface area with the thinner slices…but waste more than twice as much glass.

The square on the left is a 6mm (1/4 inch) thick piece of pattern bar. The two slices on the right are 1.5mm and 2mm thick, respectively. The center slice shows far more of the layer detail.

The square on the left is a 6mm (1/4 inch) thick piece of pattern bar. The two slices on the right are 1.5mm and 2mm thick, respectively. The center slice shows far more of the layer detail.

Next best: Better color control

There’s another, less expected benefit to this, too: The thinner I can slice, the more choices I have with color. In pattern bar, you’re stacking one color atop another, and deep colors can quickly overwhelm each other and go black.

I typically stick with the lighter half of my glass color palette when I’m designing a color way, to avoid winding up with a lot of muddy blacks and browns.

If you can slice the bar very, very thin, you don’t have to worry about that. Thin slices open the color palette back up, even allowing dark purples and blues without loss of detail.

Here’s an example: I made this pattern bar out of Bullseye Gold Purple, Carnelian, and Cobalt Blue, all very deep-toned glasses. The first slice, the little 6mm square on the left (1/4 inch) shows why you don’t use those colors in a pattern bar: The only real detail you see are white spots and a little orange.

Check out the slice on the far right. It’s 2mm thick, and reveals far more detail than the 6mm piece. The center piece, at 1.5mm is even brighter, and the detail is popping out even more.

2. I must control blade wobble.

There’s probably an expert term for “side-to-side movement of a saw blade on a fast-moving spindle” (see below, from Chaniarts–it’s called “runout”) but I just call it wobble. A saw blade can wobble because there’s some play in the way it’s attached to the spindle/axle-thingy (the nut’s not firmly tightened, or has vibrated loose, for example). Or, as might happen with the thin Result blade, the blade can be thin enough that it flexes at high speed.

A wobbly blade can widen the saw kerf, make a rougher, wider cut that wastes glass, and is also more likely to chip or break the glass.

Obviously, tightening the nuts that hold the blade on the spindle is part of the solution, but I also invested in blade stabilizers from HIS (I think they call them “wheel stiffeners.”) The stabilizers look like great big washers–I suppose if you could find great big washers they’d work as well–and they go on the spindle on either side of the blade to prevent wobble.

tilesaw-calloutsThey definitely make a difference–less chipout. The downside is you lose some depth in your cuts–without stabilizers, my 10-inch tilesaw can cut a maximum depth of almost 4 inches (although that’s puuuushing it). With the new stabilizers, I have a tiny bit more than 2 inches. But the cuts I can make are almost exactly the width of the blade, without chips.

3. The deeper or thinner the cut, the more water I use.

A moderate trickle of water against the blade suffices when I’m cutting flat (6-9mm) pieces of glass. I find I must really pile on the water, however, when cutting thick pattern bar, castings or murrini slices.

I invested in some Loc-line hoses, one for each side of the blade. I aim one at the blade that’s in the cut, right at the base. The other I position so it’s shooting water into the cut, almost on top of the front edge of the blade. Then I attach the garden hose and turn on a nice stream–if I’m not getting drenched, I can’t cut as thin. (Again, experts may have a better way to do this).

tilesaw-waterpositionThe loc-lines make it easy to position water exactly where I want it. I adjust the water position every time the cutting depth changes, which is why the easily adjustable loc-lines are so important.

I do NOT recirculate water from a pump in the reservoir–it doesn’t work all that well on my saw anyway, and when the water clouds up my cutting action suffers. So I use fresh water, and accept that I’ll be sending a stream of water down my driveway (where it excites comment from my water-conserving neighbors).

4. I use sacrifice glass to prevent blowouts and lost corners.

A traveling saw blade puts a lot of pressure on the last little bit of glass going through the saw, which can blow out the back of the hole, or knock off that last corner. This is a problem in woodworking, too; woodworkers solve it by putting a piece of scrap wood behind whatever’s being cut.

So do I; only I stick a piece of glass behind the piece I’m cutting on the tile saw and make the cut continuous through the sacrifice piece. That way, any breaks happen in the sacrifice piece, not the real thing.

This can be tricky to get right because the two pieces of glass must connect or the first will crack without affecting the sacrifice piece. Typically, the sacrifice piece can vibrate loose and you the back anyway. If the glass is perfectly flat, I use a little water between them and let suction hold them together, and secure them with a tight wrap of duct tape. Or I superglue them together (VERY lightly) Usually I get the glass wet enough that you can separate them later.

HIS sells a special sticky wax, “Stacking Wax,” that can be used for the same purpose. I haven’t tried it, so I don’t know how easy it is to use. If you have, let me know how it works.

I’ve been told that you can also use stacking wax, other soft, sticky wax or an adhesive-backed vinyl or lamination layer by itself in much the same way, without the sacrificial glass. Apply it to the back of the glass and make your cut; it’s supposed to hold the glass together to prevent the initial crack that starts a blowout. Again, I haven’t tried it, so I’m not sure that it works.

5. I ensure my feed table is straight and true to the blade.

Yeah, right. To put it bluntly (hah!), mine isn’t true and it isn’t adjustable, which is a big headache. At best, it can cause my slices to get fatter or thinner as I move along. If I’m not careful, it also can put pressure on one side of the slice, and cause it to break.

I compensate by making my own jigs to line up the glass. I true THOSE to the saw, which sorta works. I fully intend to use my el-cheapo saw until it dies…but if anything could make me break down and buy a good saw before that, that daggone feed table would do it.

6. I don’t mess around with a good blade.
I use my cheap blades for freehand carving in the glass, kinda like chainsaw sculpture in wood. You bring the glass to the bare, moving blade and use it to dig into the glass and rough out your shape, literally whittling things down. I do NOT do that with the Result blade. It’s possible to torque a thick piece of glass when you’re in the middle of a freehand cut, with an outside chance that it would damage the blade.

I do sometimes make freehand cuts with the Result blade if I need to quickly cut a thick piece down to size. I just don’t expect it to be accurate because I know I’m not going to hold that piece perfectly straight all the way through to the end of the feed.

If the bottom of the glass doesn’t sit flat on the table I’ll try to stabilize it with a shim instead of just holding it upright. I’m not that worried about tilting the glass and bending the blade, but I am liable to change the angle of the blade’s attack, which increases the likelihood of chipping or breaking the glass.

I keep a supply of “craft sticks,” AKA popsicle sticks, on the saw table just for this purpose. They’re inexpensive and reusable, and long enough that I can usually manipulate a couple around under the glass until it stops wobbling.

7. I take CARE of that blade.
Result blades–or any good glass saw blade–aren’t cheap. I clean off the glass particles, dry the blade and periodically clean and lubricate it between uses.

When I’m using it, I never push a cut. If it changes noise/pitch in unexpected ways while I’m cutting, or I start seeing a lot of chipping in the glass, I stop and figure out what’s going on before I proceed. I may beat that saw to death…but the blade gets gentle treatment.

If I’m hacking through a lot of glass fast and don’t need the thin, smooth slices, I swap out the Result for one of the old diamond blades–no need to waste a fine blade on thick cuts. I also dress the blade when it appears to be slowing down. HIS and other places sell dressing sticks for this purpose; I use broken mullite kilnshelves to expose fresh diamond in the blade, and it seems to work fine.

And that’s it. Nothing magical, and I’m probably doing something I shouldn’t, technically speaking. But I’m getting the cuts I need.

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*Technically, what I’m making is pattern bar, i.e., stacked or dripped glass block that makes beautiful, Rorschach-like patterns when sliced open and combined. I call what I’m making “murrini cane stock,” essentially pattern bar with a tiny, repeating pattern. It’s designed to be sliced into identical bars (cane) that can be sliced up into murrine.

Awhile back I made and hundreds hundreds of cabochons for buttons, pendants, earrings and rings from the pattern bar stock I built out of these experiments, and I still have maybe 2/3 of that stock left. If you’d like to see how these were made, check out these posts–the “sandwich” post talks about the bars: