Chipping Glass while Sawing

Frequently there are chips on the bottom surface or breakouts at the end of cuts while sawing glass. There are several methods to reduce these effects.

Saw blade depth

The blade on an adjustable depth overhead saw should be set to just below the saw table depth. This reduces the break outs on the bottom surface. It helps to make the angle at which the saw blade meets the glass more acute, helping to reduce the chipping of the surface.

Of course, on an adjustable overhead saw blade could be set to just mark the surface to reduce chipping on the top. Then the table drawn back to adjust the blade to the full cutting depth. However, that is a lot of adjustment to reduce minor chipping that will be remedied in further cold work or fire polishing.

For saws that do not have adjustable depth, bottom surface chipping can be reduced by placing sacrificial glass below the main piece. This raises the main glass and creates a more acute angle between the glass and the blade, also reducing chipping on the upper surface.

Ends of Cuts

Break outs often occur at the ends of the cuts. Placement of a sacrificial piece of glass vertically at the exit of the cut helps to give a clean cut at the end. This will apply whether using a fixed or adjustable saw blade.

Of course, the two can be combined:

Grinding out Chipped Edges

Sometimes the edge of a drop vase is chipped during the polishing process, or more frequently, during use. What to do?

 Grind the edges down until the chip disappears. This seems like an obvious statement. But it is often overlooked.

 

 

The grinding can be at a slight angle to the length or parallel to the base of the piece. The angled grinding removes less glass but needs a jig of some sort to keep the angle consistent. The difficulties of obtaining a consistent angle grind, makes grinding a flat edge simpler.

 You can do this flat grinding and polishing by hand in only a half hour or so. Although a flat lap or belt sander will enable you to do it more quickly.

 You have to be careful while griding, especially when using the rough grits, to avoid small chips on the new edges. One trick I learned is to make a small bevel or chamfered arris the edge before doing the flat grinding.

 

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 If it is a large or deep chip you are grinding away, you will need to do it in stages.

 You do not want a large arris at any stage. It is possible to create such a large arris that you have to grind more glass away than the original chip would have demanded. When the grinding comes close to the end of the arrised edge, stop. Make a small arris on the edge again before continuing to grind the face. Repeat this as often as required until the chip is removed. 

 Make this arris at the start of every finer grit. The arris will not need to be so big as for the first, rough grinding. You are not taking off as much glass on the surface. But the arris will prevent tiny chips appearing at the edge of the polished surface.

 I give a final arris the polished edge. This gives a pleasant roundness to the edge. It also keeps the edge from being delicate and subject to further chips.