glass drill bits

[Cal_stir]

i put a 2 inch bulkhead 2 inches from the bottom of my 80 gal sump

[Myka]

I won't drill any closer to the edge than the size of the hole (not the size of the bulkhead) or 2", whichever is bigger. So if the hole is 1.75" I drill 2" away from the edge. If the hole is 2.5" I drill 2.5" away from the edge.

[rastaangel]

Industry standard is half diam. of hole from edge unless tempered. But for external pumps I usually go 2"+ from edge.
And FYI a tube bit with graphite will produce a much cleaner hole then a diamond embedded bit but will be harder to find and requires a tripod to drill

[monocus]

see how high your pump sits against your sump and drill accordingly.i can lend you a hole saw

[e46er]

Ok thats kinda what I was thinking for height good good

Monocus you have PM