I just measured a 1" bulkhead I got from J&L and it will just fit a 43mm hole.

Sorry about that: It is a 3/4" bulkhead, my bad.

Yeah I think I am pretty much stuck with going with a smaller bulkhead... It's a 30 G frag tank to be plumbed to my main system. I may just need to limit the flow a bit to the tank....

42 mil is 1.65", get a lighter schedule bulkhead.

Are they schedule 40 bulkheads (black) or the schedule 80 (grey I would think)?

Can you post a picture of how far in they go into the hole?

I think you can drill over the holes if need be. You'll need a plant sprayer to spray water as you go instead of the usual trapping-water thing you usually have to do. I've used the spray bottle when drilling holes on glass I couldn't get horizontal like on a tank too big to turn sideways.

No idea how risky it is.

If it's just 1mm short maybe a dremel with diamond bit to grind out the holes to make them large enough?

Or, just use the 3/4" bulkheads but step it up to 1" on either side. Would make for a small restriction but maybe not much worse than a typical 90-degree thing.

Great suggestions

They are the schedule 40 black ones. I think I am going to go with your last suggestion. I have already experienced the whole square peg round hole thing, I think I want to go with the easiest solution. thanks

BRS also recommended using a dremel and smoothing out a bit and stood by the measruements that it should work. So I pulled the old dremel out and in less than a minute each I was able to get the 1 " bulkheads into the 42 (now probably 43 mm holes. Yay success! Thanks everyone.

Awesome! What kind of bit did you use?

I had a similar problem when I drilled my nanocube. The hole was maybe 0.8mm too small to fit the bulkhead completely in.

Used a dremel bit just like this (see below), and went to town. I ran the tool around the hole, against the rotation direction of the bit .... and kept just going around and around quickly. I can be done dry, and it only took about 5 minutes per hole to get a perfect fit.

http://www.tooled-up.com/Artwork/Pro...2615712332.jpg

I didnt use that one (didnt have it.) I cant find a picture of the bit I used but it is basically a rod that tapers to a point with the diamond on the outside of about a cm of the tapering portion. So I basically moved the side of the rod in a circular fashion on the inside of the hole.