I’ve been thinking about whether or not I should drill holes in glass before or after fusing.
On the one hand, drilling the holes in a finished piece gives you complete control of exactly where the hole will be. But on the other hand you end up will a sharply defined hole and may have to drill through a thicker quantity of glass on a surface that is not smooth and flat. The risk of the drill bit slipping and leaving your finished piece with a nasty scratch is another problem.
So, maybe you will also find it better to drill the hole and pack the hole with some ceramic fibre rope before you fuse. You can see what I mean in the picture where there’s a before-fusing and two after-fusing examples. You can also see that you lose some control of the size of hole that results – the smaller hole resulting from less tightly packed ceramic fibre rope. Dealing with a stack of fusing glass is a little more complicated as you have to drill more than one pieces of glass in exactly the right place and then pack them all with a single piece of ceramic fibre rope.
Notice also that the resulting holes are more rounded with less sharply defined edges that are softer – nicer I think.
And you may want to consider what type of drill bit to use – and there are several kinds to choose from – pointy ones that I can’t cope with, hollow ones that tend to be for larger holes and burrs that are similar to what a dentist uses. What I find easiest is to use a ball-shaped diamond burr, again illustrated in the picture. They are quite cheap and can last quite a long time if you ensure that you don’t apply too much pressure and keep everything cool with plenty of cold water when drilling out the hole. And if your drill bit slips and scratches the glass it doesn’t matter – it will disappear when you fuse the glass!