Cutting Remarks

It’s all in the way you slice it. And the way you slice it is profoundly affected by a good blade.

Check any glassmakers’ forum and you’ll see a lot of tilesaw complaints, usually because someone’s is cutting glass about as well as a wood chipper. They run a perfectly innocent pattern bar through the thing and, instead of pristine slices, they get a ragged slice with scalloped edges…and a lot of frit.

This post is about how I fix that.

Mind you, I am NOT a coldworking expert, and it’s not like I have a $50K glass saw. My tile saw is an old, cheap, very badly made and out-of-true no-name model from China, $100 on eBay. I bought it because I’d just bought a house, was out of money but needed to tile the bathroom FAST, before the furniture arrived. (I mean, who puts WHITE CARPET AROUND A TOILET?)

My construction-manager brother-in-law laughed when he unboxed that saw. “THAT,” he said, “Is the crappiest saw I’ve ever seen. It’ll be broken before we finish the bathroom.”

He said that in 2003 and that stupid saw is still going strong (hah, Jerald!). I hate that saw, wish I could buy a brand new one that actually had fun stuff like a working water pump, but the old one shows no sign of quitting.

Plus, it makes remarkably fine cuts in glass sheet, sculpture, and pattern bar, such as the pattern bar slices I’m showing in the photo.

Take, for example, the pattern bar slices shown at the right. I cut these from murrini cane bars; they range from about 1.5mm (thin as a dime) to around 4mm thick. The two on top are Bullseye thin and 3mm sheet glass, for comparison.

This aren’t one-off miracles: I’ve been making these cuts with that lousy saw for years. If I can do that, I must be doing SOMEthing right…right?

WARNING: If you’re an experienced coldworker, this will be a boring and repetitive post, so please feel free to make it even MORE boring and repetitive with your useful tips and corrections in the comments below. I’m not an expert in shop equipment terminology–as you can tell by the comments–and I’m sure as heck not a coldworking expert.

If you aren’t, either, I urge you to get a couple of books on coldworking (Johnathan Turner’s coldworking book is one), view some coldworking videos on YouTube (HIS Glassworks has some great ones), and better still, take a class in coldworking and glass tools.

Me, I’ve studied those references, taken classes, and made many dumb mista…, er LEARNING EXPERIENCES, on my own. Somewhere along the road I developed my own Rules for Effective Tilesaw Management.

Caveat–these are MY rules. Probably there are better ones out there, so please speak up

1. It’s all about the blade.

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

But those blades are 2mm thick (about .085 inches). My goodness, they take a HUGE kerf out of the glass. (Kerf: Material removed by the blade–it’ll be a little wider than the thickness of the blade plus in most cases)

With those original blades, I lose around 3mm PER SLICE, i.e., every pass of the saw eats the thickness of a 3mm sheet of glass.

Worse, that blade chips my cuts like a moth…(never mind). If I’m very, very careful and go slowly, I can make a 3/8 inch thick slice with the aforesaid scalloped edges and a fair amount of frit. That’s about the limit.

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, and the diamonds are much finer.

It 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 the saw kerfs are less than half width of the previous kerfs. As long as I make the same size of slices (more about that in a sec), I’ll waste half the glass.

The best part: Thin slices

The Result blade lets me slice a 2-inch thick block of glass, 10 inches long, into slices as thin as 1mm, but more reliably, about 1.5mm. Thin slices are a big advantage in many ways, especially when it comes to giving you more surface area coverage from a pattern bar.

That does NOT necessarily mean that you waste less glass overall, interestingly enough. In fact, the thinner you cut, the MORE glass you’ll lose. It sounds counter-intuitive, but if you do the math you can quickly see how this works.

Let’s take my old blade versus the Result blade. If I cut the same number and thickness of slice with each blade, then yes, the thinner blade will save glass. But I’m after thinner slices, so if I push that Result blade to the limit, make as many cuts as possible in that pattern bar, well, here’s what happens:

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

So you’re getting much thinner kerfs, but a lot more of them. See how it works? I can get triple the surface coverage with those thinner slices, but I’m losing more than twice as much glass as with thicker slices.

Good blade = Better color control, wider palette

There’s another, less expected benefit to a very thin, stable blade: The thinner I can slice, the broader my color palette can become, giving me more control over the final appearance. Glass gets darker and darker the thicker it gets (less light is getting through), so most people avoid piling on strong colors to keep the slices from looking black.

You don’t have to worry about that, however, if you can make ultra-thin slices. They open up your pattern bar color palette, so you can add in deep purples and saturated cobalts with abandon.

Here’s an example: I made the pattern bar pictured from Bullseye Gold Purple, Carnelian, and Cobalt Blue, all very deep-toned glasses. My old saw cut the thinnest slice it could (6mm with a lot of chipping), the little square piece on the left.

It amply demonstrates why you should never use those colors in a standard pattern bar. The only real detail you see is are some light yellow/white layers and a few dots, swallowed by what looks like a dark brown background.

I cut two more slices with the Result blade. The slice on the far right is 2mm thick: See how much more color detail you get? The center piece is even thinner, 1.5mm, and it reveals even more detail.

2. I must control blade wobble runout.

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 wobbles, er, exhibits runout when 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 can happen with the thin Result blade, the blade is simply so thin that it flexes at high speed.

A wobbly blade widens your saw kerf, making a rougher, wider cut that wastes glass, and usually increases the chipout and frit-making issues.

Obviously, tightening the nuts that hold the blade on the spindle is part of the solution. 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 steady it during rotation.

Upside: Stabilizers definitely reduce chipout.

Downside: You lose a lot of cut depth. 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.

Still, with stabilizers installed, my cuts I can make are almost exactly the width of the blade. And I don’t get chipout.

3. The deeper/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. When cutting thick, however, I find I must really pile on the water.

Basically, if you’re cutting pattern bar but you don’t look like you’ve jumped in the pool with your clothes on, get more water into that cut.

I invested in some Loc-line hoses, one for each side of the blade. I aim one at the blade, down in the cut, right at the base. I position the other Loc-line so that it shoots water directly into the cut, almost on top of the front edge of the blade. Then I suit up in my rain hat, rubber apron, and gloves, turn on a moderate stream of water, and start cutting. (Again, experts may have a better way to do this).

The loc-lines make it easy to position water precisely where needed. And I will re-adjust the water position every time the cutting depth changes, which is why the easily adjustable loc-lines are so important.

Also, I do NOT recirculate water from a pump in the reservoir. As I mentioned, the water pump on my saw is useless anyway, and even with a new pump I’ve noticed that, as soon as 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 whirring saw blade puts a lot of pressure on that last little bit of glass going through the saw, which can blow out the back of the cut, 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. 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. (I kinda wonder if you could use wood instead of glass and get the same result…hmmm…)

The two pieces of glass must connect as a continuous piece, or it won’t work; the first piece will still crack. Or if the sacrifice piece vibrates loose, you’ll blow out the back anyway. Sometimes, if both pieces are perfectly flat, I can get them wet, stick them together and let suction hold them together.

More often, I need to use double-faced tape between the pieces, or wrap them into a single package with duct tape.

A very light coat of superglue can work, too, if the pieces fit together. It will hold through the cut, but the glass usually gets wet enough that the superglue will loses its grip after vibrating through the saw. If it doesn’t, I just soak it in a little water and (gently) use a palette knife or similar to pry the pieces apart, but that’s rare.

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 well it works. If you’ve used it, let me know.

I’ve been told that you can also just apply a thick layer of soft, sticky waxes, an adhesive-backed vinyl, or lamination sheet to take the place of the sacrificial piece. You pile it onto the back of the glass to maybe a half-inch thick, then make your cut; presumably this holds the glass together and prevents that blowout-starting initial crack. I’ve never tried it–scrap glass is much easier to grab and it’s free–so I’ve no idea how well this works.

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

Yeah, sure. MY tile saw’s feed is about as true as a politician’s campaign promise and it can’t be adjusted; that’s what you get when you buy a crappy saw. It’s a real headache, and if I use the feed table I can guarantee that my slices will get fatter or thinner as I go along. Worse, if I’m not careful, I’ll put undue pressure on my cut, causing it to shatter.

Instead, I ignore the silly feed and make my own jigs for lining up the glass. I true THOSE to the saw blade. It (mostly) works.

However…while I fully intend to use that @#)*(&$#)@ el-cheapo-but-cost-effective saw until it dies a horrible death…if ANYthing could make me send it to the dump tomorrow it would be that misaligned bloody stupid feed table.

6. My good blades ONLY do precision cutting.

A table saw is marvelous for slicing up ceramic tile (which is, after all, its intended use). It’s also excellent for quickly chopping big glass billets into more usable chunks, roughing out stone slabs, or freehand carving in cast glass. (That last is kinda like chainsaw sculpture in wood, only with glass. You remove the blade guard (not hard with my saw, it keeps falling off), then bring your glass to the bare, moving blade, carving directly into the glass as you turn and twist the piece. It’s a lot of fun and a very very fast way to get a rough shape when sculpting.)

I do those things, however, with those old nasty diamond blades that came with the saw, not with my umpty-ump dollar fine glass blades. It’s all too easy to torque the blade while you’re in the middle of a freehand cut; the thicker blade can stand up to that punishment, and if it can’t…who cares?

That also means that I make a lot more of those jigs I mentioned, to ensure that I’m keeping the glass straight throughout the precision cut. 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 don’t just freehand an oddly-shaped piece of glass through the saw; there’s too much danger I’ll change the angle of the blade’s attack, which increases the changes that I’ll bind the blade (get it stuck in the cut) and potentially damage it, or crack 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. A little TLC helps them last longer. First, I don’t leave them wet and covered with swarf (the glass+diamond+whatever crud that accumulates during coldworking) after a cutting session. I clean off the glass particles and dry the blade. If I’m done for the day I apply a little light machine oil to the blade to help preserve it from rusting.

During use, I never push a cut–I let the glass feed itself through the saw as much as possible; I’m just there to guide it. If the cutting sounds change noise or pitch unexpectedly, I start seeing a lot of chips flying, or black streaks from the saw appear on the glass, I’ll back the glass out and stop. I won’t start again until I figure out what’s going on and fix it.

I beat that bloody awful saw to death…but the blade gets gentle treatment.

I also take the time to replace the blade when I’m hacking through a lot of glass fast and don’t need those ultrathin, smooth slices. The finer cut really won’t buy me much, and I’m not only extending the life of the blade (diamond blades DO grow old and die, you know), I’m also reducing the chance of damaging it.

I also dress the blade when it appears to be slowing down. HIS and other places sell dressing sticks for this purpose, but I use broken mullite kilnshelves to expose fresh diamond in the blade. So far, it seems to work fine.

And that’s it. There’s no magic secret here, and I’m probably doing something I shouldn’t, technically speaking. But it works.

---

*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:

• Murrini cane in a kiln: Sandwiches, Part I
• Murrini cane in a kiln: Jellyrolls
• Kilnformer’s murrini you can buy
• Murrini cane in a kiln: The rod pod