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Need advice on drilling holes in the sides of an acrylic tank (1 Viewer)

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capman

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So, I have a 180 gallon acrylic tank at home that currently has some Malawi cichlids and Tanganyikan catfish.

As discussed in another thread, my strategy of using a bunch of large sponge filters has never provided enough mechanical filtration, and I'd like to take some measures to address this.

Also, I'm contemplating turning this into either a brackish tank, or a full blown saltwater fish only tank at some point (maybe around December or so). All of this is increasingly making me want to be able to hook this tank up to a sump.

I'm thinking of setting up some simple overflows consisting basically of tubes/pipes made of some sort of coarse screen or mesh, positioned where I want the water level to be. My tanks in the lab by the lab window are set up like this (some of you have seen this arrangement - I have tubes made of plastic canvas material) - it is simple, resistant to clogging, keeps small creatures from accidentally ending up in the sump (assuming they are bigger than, say, amphipods), and actually works quite well.

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But how do I drill holes for bulkheads in acrylic?

I've drilled holes in glass tanks for 1" bulkheads, and I have a diamond hole saw for this. This involved having water flowing over the hole location to flush it out and to keep it cool while drilling.

But what sort of hole saw is used for acrylic?

  • My guess is that a big issue is having the acrylic melt while drilling, and having the saw get gummed up.
  • Do I use my diamond saw, or will I just wreck it if I try using it for acrylic?

And what are the special challenges and problems and techniques involved in drilling acrylic?

  • Do I need to be flushing the area with water as one does when drilling glass?
  • How likely am I to end up cracking the acrylic if I do this badly?

And would it be feasible for me to just lower the water level and drill these holes with the tank set up, or do I need to empty the tank and everything (and potentially relocate the tank) to drill these holes (I'd be wanting to use 1" bulkheads, which if I recall correctly calls for a 1.75" hole maybe?).

Thanks!
 
Disclaimer: I have not drilled an acrylic aquarium before nor did I stay at a Holiday Inn Express last night.

I would assume you could use the standard hole saw commonly used for woods and plastics. It's what I use when I need to make large holes in polycarbonate.
The teeth on the hole saws are offset so that the kirf is wider than the drum of the hole saw. The wider kirf allows the chips of acrylic to be vacated while the teeth cut the acrylic.
To me, a diamond coated hole saw seems like it would melt the acrylic as there's no "teeth"; more of a grinding action versus a cutting action.

While cutting the holes, I would apply steady pressure when cutting, but I would also pull the saw out frequently to allow the saw to be cleared of chips.
If this was my tank and I wanted to cut the holes while the tank was still in operation, I would buy a brand new saw to guarantee the sharpest teeth.

Good luck!
 
I've never drilled acrylic before, so I can't answer the heat/melting question, but I'm pretty sure you use regular wood hole saws from the hardware store for acrylic.

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Regular hole saw, pilot bit would be wise. no water needed, go light pressure especially when getting near the end if you push to hard or start to go crooked the bit will bind up and get the heart pumping. I drilled two holes in the top of my tank and just used a large fish net underneath to catch the shavings and puck when it fell through. But tank was fully running while I did this (3/4" acrylic)
 
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Thanks.

I was kind of thinking a standard hole saw would be the way to go. And yes, a new sharp saw would probably be worth it.

I should probably do a test drilling on a scrap of acrylic first (I have some thinner acrylic around in the garage somewhere) to get a better sense of how the hole saw is likely to behave (and maybe I'll try intentionally getting it to bind up to see what happens, to see how easily it binds up).

My guess is that, as recommended above, having a sharp hole saw, and going nice and slow and steady are the key things.

When I drilled glass tanks before, I did it free-hand, with a piece of wood with a big V-shaped notch in it clamped or taped onto the tank to serve as a bit of a guide (this was following the advice on how to drill tanks from JehmCo, which is where I got the diamond hole saw). I probably would be better off with a drill guide of some sort. Do any of you have one that you have used for this purpose that you would particularly recommend I get? I guess I need to do some Googling to see what the options are.
 
Now the question on my mind is: How close together can I put the holes? Hmmm....
 
capman said:
I probably would be better off with a drill guide of some sort. Do any of you have one that you have used for this purpose that you would particularly recommend I get? I guess I need to do some Googling to see what the options are.
Click to expand...

You don't need / wouldn't want a drill guide for a standard hole saw. That is what the pilot bit is for. The pilot bit is usually a 1/4" bit (I think), so if that makes you nervous about it walking before it grabs, you can use a smaller 1/8" bit to make a pilot hole for the larger pilot bit.

I would also get a decent hole saw specific to the size of hole required for your bulkhead/s. Yes, I'm going to bad mouth the set they sell at BRS and Harbor Freight. These tend to not spin true and it may also not have the right size in the set - both scenarios will cause your holes to be slightly oversize and have more potential for leaks. Some hole saws have the arbor built in (Morse brand for example) otherwise you'll also need an arbor, and don't forget to find a pilot bit for the saw!
 
Thanks everyone.

These overflows look really appealing - the Custom Aquariums one especially, since it seems the side slots are smaller and it would be less likely for small critters to end up in the sump. It also sounds like it moves more water (maybe just because it is designed to be used with a 1.5" drain hose?).

The pulsing flow they talk about in the video about the Two Little Fishies version is interesting, but I don't understand enough about the design of that device to have any clue as to why it would do this.

_____________________________________________

Moving away from my home tank for the moment:

I've been thinking a lot about what sort of overflow arrangements I want to have on the display tanks in the new building. I have never liked big corner overflow arrangements, because I don't like so much tank real estate being taken up, because I really don't like dealing with the plumbing fittings in such an arrangement (SOO awkward reaching in, and also so awkward working under the tank), and I don't like the idea of having holes in the bottom of a tank (which, as Julian Sprung said in the video could in extreme failure situations basically drain a tank).

Overflow boxes with plumbing coming out the back are better, but still have issues.

I think I'm going to be going with either the Custom Aquariums overflow, or the Two Little Fishies overflow (if I figure out how it works better). Probably I'll go with the Custom Aquariums one.


Does anyone here have any first hand experience with the Custom Aquariums overflow?
 
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