Hole location for Herbie for overflow's

Palmer · #1 01-31-2011, 03:40 PM

Hello,

I am planning on drilling a couple of hole's in a tank to make an internal herbie overflow. The hole's are going to be 42mm (I believe dont have the saw size with me at work) to support two 1 inch pvc pipes for a frag tank.

Queston- Is there a standard minimum distance from the edge of the tank you shoot for to maintain structural integrity of the glass? Or is something like 1 inch enough? I am putting these in a standard 30 G all glass tank.

thanks

Delphinus · #2 01-31-2011, 05:02 PM

I just make sure I have enough space that the bulkhead rim has enough of a gap around it and won't interfere with the stand underneath.

If you think about it, drilling near the edge is probably better than further away from the edge since the flex is minimized due to the edge being braced so to speak (by the seam of the vertical wall). I'd be more worried about holes in the middle of nowhere.

Only thing about drilling a 30g tank: make sure the panel you're going to drill isn't tempered (do you have polarized sunglasses? that's a good way to tell usually if there isn't a sticker) and don't overtighten the bulkheads: I've busted many smaller tanks (1/4" or 5mm glass) by tightening "one more quarter turn ought to do it".

The Codfather · #3 01-31-2011, 05:05 PM

I think a 1" bulkhead requires a 1 3/4" hole.
I might be mistaken but I think you need at least 1xdiameter from the edge.
Don't take this as law, it's just off the top of my head.

Palmer · #4 01-31-2011, 05:07 PM

Thanks Delphinus

Good points about the placement. I was just thinking if you make the hole to close to the edge it may facilitate a crack from the hole to the edge. Like a stress crack etc

Current ALL GLASS info says its not tempered but I bought this thing in 1998 so who knows. This will reveal my stupidity but what are polarized sunglasses? Do they just have a little sticker in the corner telling you they are? Can I get a pari at Walmart and what will I see if it is tempered??

The Codfather · #5 01-31-2011, 05:15 PM

U tube.
It shows a clear demo. what to look for.
I will see if I can find the link for you.

http://www.youtube.com/watch?v=dUA6nyvy-LY

Delphinus · #6 01-31-2011, 05:16 PM

42mm is I think pretty close to 1-3/4" ? It will probably work OK but just eyeball the hole saw to the bulkhead before drilling I guess - it would suck to find out it's 1mm too small or something.

I'm not sure if closer to the edge increases the risk of a crack. Go slow and easy and real gentle on the pressure as you're just about to poke through. The times I've cracked glass while drilling has always been at that point where it just breaks through to the other side and I suspect in each case it was because I lost patience and pushed too hard. If it's your first time drilling maybe try a practise run on some scrap glass. It's really not too bad though, just slow speed and gentle pressure and basically you sand or grind the hole out rather than "drill" it out per se.

Polarised sunglasses are where instead of tinted lenses you have little microscopic lines running across the lens. It's to help reduce glare off reflections of sunlight. I'm not sure if you can get them cheaply, I have coke bottle glasses and usually have to spend a few hundred per pair of glasses so getting the polarised lenses for shades is doesn't make a signficant difference in the cost so I have them but have no idea what the uplift was for that, sorry.

When you look at tempered glass through polarized lenses you can actually see the checkerboard pattern produced by the tempering process.

Palmer · #7 01-31-2011, 05:16 PM

Quote:

Originally Posted by The Codfather

I think a 1" bulkhead requires a 1 3/4" hole.
I might be mistaken but I think you need at least 1xdiameter from the edge.
Don't take this as law, it's just off the top of my head.

These are the bulkheads I am planning on using.

http://www.bulkreefsupply.com/store/...-x-thread.html

Looks like its greater than 1.5 " for this bulkhead its listed as 42 mm. That is the size of the diamond hole saw I ordered.

I was thinking of going at least that much out (1") just to be safe. Makes sense...

The Codfather · #8 01-31-2011, 05:22 PM

1 5/8" to 2" should work.
42mm to 50mm.

Palmer · #9 02-25-2011, 03:48 AM

So I drilled three holes in the tank tonight with the 42 mm diamond saw and wouldnt you know the 1 " bulkheads DONT fit!! It goes right up to the external thread (about a half a cm in) and just stops doesnt seem like anyway to get it through. I wrote BRS an email but honestly all the 1 " bulkheads they sell have the external thread so now I dont know what my options are...

Anyone run into this before?

The hole is pretty clean there really isnt any significant jagged edges....

Palmer

Palmer · #10 02-25-2011, 04:07 AM

It seems under the 42 " diamond saw it says its for 3/4" bulkheads. But from what I could see on the 1 " bulkhead it stated the hole size needed was 42 mm.... You just cant win sometimes... Guess I am stuck with 3/4 returns and herbie drains unless someone can think of something else I can do. You cant drill a bigger hole where the smaller one is can you? Not sure how practical that is and how to trap the water needed for the drilling...