Drilling an extra hole

[paddyob]

Originally Posted by 2pts

The way I have done it is to predrill a piece of plywood with a wood bit the same size or slightly larger, clamp that piece of plywood to the front with the hole lined up where you want to drill your new hole. It will give your glass hole saw a guide so your not having it spin off and cracking the glass.

Clamp an undrilled piece of plywood to the back of the glass and dont forget the water running on the hole as your drilling.

That said, after reading this thread, I would probably switch the plywood around part way through, and drill from both sides.

Also you need to find out if that pane of glass is tempered, if it is, all this is a no go.

If the tank was previously drilled... Is it safe to assume not tempered? Already three holes when I bought it used.

Back drilled.