Originally Posted by Granville
DRILLING TANKS
This is my method for drilling tanks, which I have used to drill thousands of holes in many shapes and sizes of tanks, both in situ containing livestock, and empty. I would point out this ISN’T the recommended method advocated by the drill supplier, as the drills were produced to cut through a single sheet of glass flat on a bench using a fixed stand method. I used to drill tanks for 2 tank manufacturers, and have also drilled in situ tanks for several shops who wanted to retro-fit a centralised filter system on existing stock tanks.
Items you will need are, sheets of glass or old tanks to do a bit of practicing on if you feel you need to, a hammer action drill (preferably mains powered), a piece of wood about half inch thick to make a template to stop the drill bit running loose on the tank, a plastic clamp to hold the template in place, a hand spray used to spray plants if drilling in situ indoors, or a slow running hose if drilling outside, which is obviously the easiest method.
1) make a template slightly larger than the drill bit into a square of decent wood, I used mahogany, as it doesn’t swell or react to water
2) decide where you want the hole, my preferred choice is top of hole about 2†from the top of the tank which gives a running depth in the tank about 1†from the top……………if you cut your template with this in mind, you will only need to clamp it in the same position on each tank to keep things uniform.
Water is needed to wash away the ground glass from the hole being drilled, NOT to cool the drill bit, which is the usual miss-conception. If you were to push the drill bit whilst drilling the hole, it would take less than 5 seconds to drill through 6mm glass, but since things will not be level, the glass will inevitably break, as one patch of the glass will be drilled first, and put pressure on the remaining. This is why I developed the hammer drill system of glass cutting which many have copied with great success.
Method one is for drilling your tank/tanks outside. Lay your tank down so that the surface you want to drill is parallel with the ground. Locate your template onto the face of the tank where you would like the hole, and clamp in place, start a slow running hose to wash the hole area to remove ground glass, it is easier if you can clamp this also, but not essential, set your drill onto hammer, the idea being that you just rest the drill bit in the template, and the hammer action of the drill will take the drill bit through without pressure from you, even when one part of the hole is pierced before the rest, the glass wont break as you aren’t putting pressure onto the glass, and drilling will continue until the glass is completely cut. Typically a hole into a 6mm sheet of glass takes about a minute using the hammer action, about 2 minutes through 10mm glass. Practice on a sheet of glass if you feel insecure about drilling your first tank.
Method two is for drilling tanks in situ. Clamp your template onto the tank, and drop the water level to at least an inch below the bottom of where the hole will be. Cover the floor area in front of the tank with old towels or something similar, start drilling. About every 15 seconds stop drilling and use the misting spray to wash off the accumulated ground glass giving the drill an easy job. Since the tank is at a different angle, and since there could be resultant earache, take this method more slowly, expecting the hole to take about 5 minutes to drill.
Once you’ve achieved hole drilling you will wonder what all the fuss was about, but a couple of obvious things I should point out,
1) don’t forget the drill bit has to be slightly larger than the outer diameter of the tank connector, so many people buy drill bits the same size as the inner diameter of the tank connector without thinking (i.e. they are using ¾ inch overflow, and therefore buy a ¾ inch drill bit!!!!!!)
2) take things slowly, a rushed hole usually means a broken tank, if the hole is taking too long to drill, it usually means a blunt drill bit, or an accumulation of ground glass slowing the process.
Hope this gives some members the encouragement they need to attempt their own tank drilling.
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