Drilling a glass sump/refugium

Ok so I'm getting ready to have my sump drilled, and I plan to use a 1" slip x slip bulkhead. BRS notes that it requires a 42mm hole, but my local glass shop likely doesn't have mm hole saws. Will a 1 3/4" hole work, or is that too big?

 

42 millimeters = 1.65354331 inches

so i would see if they have a 1 5/8"

 

I drilled my own hole using a 1 3/4" glass hole saw from gl*******s.com for a 1" bulkhead. But on gl*******s.com it says the 1 3/4" hole saw is 45 mm..

 

verry close but not exactly


45 millimeters = 1.77165354 inch

1.75 inch = 44.45 millimeters

it dose not convert evenly so just as close as possible

you want the bulkhead to have a little room around it. so it slips in and out of the glass with out touching the glass. dose that make sense?

 

Ok so If I drilled 1 3/4 i would have 2.45 mm of "slop" which sounds like it would be fine for $15, which is cheaper (and safer!) than me buying a bit and trying to do it myself.

 

Tank drilled perfectly - whew. And 1 3/4" works perfectly for a 1" bulkhead in case anyone wanted to know.