Drilling tank from both sides question

[vtecintegra]

I'm going to be drilling my tank for an overflow. Ideally, I want no chip out, so I'm debating if drilling from both sides would be a good idea. Some tank manufacturers are doing this. Curious if anyone else has tried it, and how it turned out.

 

[Gtinnel]

I've only drilled a tank once so I have basically no experience but I would think that getting the saw prefectly lined up from both sides would be a challenge. Also from the holes I drilled there is very very minimal chipping if you apply as little pressure as possible to the drill, especially when about to break through.

 

[Reefer Reboot]

I have always drilled holes in this manner for the best results. Tip, use a drilling jig to keep the pilot hole from getting elongated. That way it will line up exactly.

 

[Gtinnel]

I have always drilled holes in this manner for the best results. Tip, use a drilling jig to keep the pilot hole from getting elongated. That way it will line up exactly.

Wait... does the glass hole saw that you use have a pilot bit? The one I used and have seen do not have a pilot bit like a normal wood hole saw. I actually cut a hole in a piece of plywood to use as a guide when I cut the holes in my tank to make sure the bit didn't "walk" on me.

 

[Reefer Reboot]

Miscommunication, I'm drilling acrylic. But the same thing could apply. If you were to drill a small "pilot" hole all the way through the glass first, you could theoretically use that to set the drilling jig in the right position before changing over to the hole saw. I personally have not done this, seems feasible to me.

 

[tripdad]

Put a piece of sacrificial material on the back side when drilling. That will greatly reduce chip out. I clamp it on but I supposed you could do something else.

 

[vtecintegra]

Put a piece of sacrificial material on the back side when drilling. That will greatly reduce chip out. I clamp it on but I supposed you could do something else.

I drilled my current tank and did just that. I used a 3/4" template for hole location and clamped wood on the other side. Went slow at the end. Very little chipping and 99% of people would have been perfectly happy. I had the idea that going from both sides could get perfection.

 

[vtecintegra]

I've only drilled a tank once so I have basically no experience but I would think that getting the saw prefectly lined up from both sides would be a challenge. Also from the holes I drilled there is very very minimal chipping if you apply as little pressure as possible to the drill, especially when about to break through.

Alignment was my first concern. My idea is to make a template in a U shape. Then drill the template pilot holes on a drill press so they are perfectly aligned. Then use the template to drill the holes in the tank. Probably sounds more complicated than it is.

 

[Gtinnel]

Alignment was my first concern. My idea is to make a template in a U shape. Then drill the template pilot holes on a drill press so they are perfectly aligned. Then use the template to drill the holes in the tank. Probably sounds more complicated than it is.

That makes sense to me, I can't see why it wouldn't work as long as the two sides are parallel when you drill the holes in the guide with the drill press. That would've been harder for me to make the guide because mine was a rimmed tank. If you're going to use a bulkhead in the hole then I'm not sure why you care if it chips out a little bit on the back side.

 

[vtecintegra]

If you're going to use a bulkhead in the hole then I'm not sure why you care if it chips out a little bit on the back side.

Just OCD

 

[Sleepydoc]

Put a piece of sacrificial material on the back side when drilling. That will greatly reduce chip out. I clamp it on but I supposed you could do something else.

This. I created a template out of ⅛" MDF to keep the drill bit stable while starting the hole and clamped another piece of MDF on the back side to support the glass while drilling. Virtually no chip out.

Go very slow at the end, essentially just let the weight of the drill do the work. Remember, you are not really 'drilling' or cutting the glass, you are grinding it so more pressure doesn't really help. Patience is a virtue!