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Drilling: safest ideal hole sizes by tank size


treesprite

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I would like to have opinions from experienced drillers, regarding the safest ideal hole sizes for tanks based on standard tank sizes (assuming standard tanks of certain sizes tend to have standard glass thicknesses).

 

I have no problem drilling multiple holes if risk means using smaller holes. I think the reason people tend to have trouble with small tanks, is that they try to drill big holes in them.

 

(Note: since I don't know the sizes of the bits themselves, I'm using bulkhead sizes).

 

IMO:

For a 5g tank, I might drill for an airline. If the cost isn't an issue, I might go with the risk of a 1/2", but have never tried; maybe I'll get a cheap 5g tank and try it sometime.

For a 10g, 1/2" bulkheads only, with multiple holes spread apart if needed for flow or whatever. IMO there is no more risk in drilling a 10g tank than any other sized tank risk, if holes are that limited in size.

For a 20g, 3/4th", with multiple holes if needed for flow rate or whatever.

For a 40g that's where I would drill for 1" bulkheads without worrying about breaking the glass, but not right next to each other, and not more than one on the ends. For 3/4th" I would drill more than one on an end if needed.

For above 75g I think 1.5 bulkhead holes are good, and typically I use mixed of 1.5 and 1.

(I've not drilled a bigger tank than that before, but I don;t think I'll ever have one so big that I would need 2" bulkheads.)

 

Just another note: I prefer drilling from the inside of the tank, with the drilling side flat on the floor. This is why I tend to drill smaller tanks on the ends instead of the back.

Edited by treesprite
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Smallest I have drilled is a 20g, and I drilled a 1" hole in that for a glassholes overflow.  

 

5g tanks have awfully thin glass.  I'd be pretty nervous doing one of those, no matter how small the hole.

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I will admit that I have taken a lot of drilling risks. I only broke one tank from drilling, in the upper corner (That's a big story, when the 2nd hole I drilled in a 65g tank put a crack in the upper corner. I took off the back glass, had the glass shop cut off the top 4", cut the length several inches shorter to cut off the end where the holes were, used glass from a 5g & a 10g to make an overflow inserted into the space where I had the top part of the back panel cut shorter... it had a ledge on the inside of the tank so it wasn't just dangerously stuck on the back of the tank, and I used that ledge for frags. Then I re-sealed the panel into the back of the tank, and used epoxy & silicone to put pieces of glass from a broken 29g on the inside and outside of the tank over the seam where I had to put the cut off top part back onto the back panel... the pieces were long enough to cover the entire length of the seam. I  didn't need to put the piece of glass on the inside - it was ugly behind the rock work - but I had 2 big pieces of glass so I used them both and felt at ease having used the overkill. It took a few months to get another tank).

 

I wish I could cut glass. I'm terrible at that, even when the glass is really thin. But still, I like to play with glass when a tank gets broken (then I take them apart and play with them).

Edited by treesprite
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I've done:

1/2" on 10g, 20g and 30g breeder

3/4" on 30g and 40g breeders

1" on 40g breeders

 

I drill from the outside, but put grey tape on the inside of the glass to support the hole when it's almost all the way through. Drilling thin glass isn't hard if you don't apply any pressure on the drill and slow the drill down. I usually borrow a guide like this (http://www.bulkreefsupply.com/glass-drill-bit-guide-thk.html) to help get the hole started.

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 I usually borrow a guide like this (http://www.bulkreefsupply.com/glass-drill-bit-guide-thk.html) to help get the hole started.

 

You can use a piece of wood with a hole drilled through it.

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For best results, I'd use _two_ pieces of wood.  One piece with a hole in it to guide the bit.  A second piece on the back side of the glass to prevent tear out when the hole bit starts to cut through.  Clamp the pieces together like a sandwich (wood/glass/wood).

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I drilled a hole for a 1" bulkhead in the side of a 10g but was constantly worried that the weight of the piping would flex/strain the glass enough to crack it. It was supposed to be a temporary setup but it was up for over a year. Although I managed it I wouldn't advocate drilling one that big in a 10 gal because of the weight/flexing issue. If you absolutely had to I would make a brace by drilling the same size hole in a piece of plexi or actual glass that is a little bigger than the bulkhead flange and silicone-ing it over the hole in the tank, and clamp it down (slowly!) with the bulkhead fitting. I had a crack that ran between two 1.5" bulkheads that were about 2 inches apart in the side of a 40b and I made a brace that covered both holes and ran it for 4 years until I sold the tank. 

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I've drilled pairs of holes for standard 1" bulkheads on several 15 gallon tanks (so the holes are larger than 1", of course). I've never had a problem.

 

I've also drilled multiple (4) holes in my 210 for 1-1/2" bulkheads. 

 

If you use a cordless drill / driver, you can choose to use one of the torque-limited screwdriver settings (rather than the drill setting) to limit the torque that can be applied. This reduces the risk of breaking the glass due to a binding bit.

 

You have to be careful with plumbing a thin-walled tank simply because a little torque on the PVC can result in broken glass. In these cases, you may be able to use another piece of glass or even wood as reinforcement on the dry side of the aquarium to help mitigate this risk.

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I have never used my cordless drill on a tank, worried it would run out of power before the hole is finished. Maybe I will try it on a small tank for the thin glass.

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They have corded drills with clutches too.

 

I find tank drilling a bit hard on drills. Mine get pretty warm. They are not intended to be run continuously for that long.

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  • 4 weeks later...
(edited)

They have corded drills with clutches too.

 

I find tank drilling a bit hard on drills. Mine get pretty warm. They are not intended to be run continuously for that long.

I have actually in more recent drilling, taken 5 minute breaks, to give my previously-broken-now-deformed wrist a rest, so it gave the drill a rest too.

 

I need to figure out where to drill these 2x20gs I got. I bought 3/4” bulkheads, not exactly sure if I'll end up drilling for that size. I want to drill them in a way that will let me use the tanks for multiple purposes.

Edited by treesprite
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