Enlarging holes in a pre-drilled tank

[EagleFF]

ok folks, I have read and looked, searched and researched.
Here is the problem, my 190 gal DSA tank came with ABS bulkheads, for lack of words these are not the best in the world, the tank hasn't been up for a year yet and already had a cracked bulkhead, the holes I thought had enough clearance for Sch 80 bulkheads so that's what I ordered, they came in and the work began of draining the overflow, and protecting the sump with towels, the bulkhead was 2 to 3 mm too big, so out came the dremel tool, I was going through sanding disks pretty quick so I began glueing 80 grit emery cloth to the old sanding drum, long story short it took me over 10 hours to get the hole enlarged on a 1/2 pain of glass, I am unwilling to disassemble tank to turn over to drill the holes, I have 4 more bulkheads I want to replace, the only thing I can come up with is drill bit extensions and drill from the top with a drill guide on inside with a bucket return pump to circ cooling water.
I had a grout saw thats diamond coated, I made a handle that would fit in the space I had to work with, it took the glass down fairly quick and finished it with fresh emery cloth. any suggestions?

 

[asdfghp]

Wow! Thats a tough one. No easy way out!
Off hand, I am thinking the following:

Construct a wooden fixture to center and stabilize the bit. Use a long extension to drill from the top. A bucket below to catch the cooling water.

OR

misappropriate a deglazing tool (equipped with course diamond or ceramic stones) which is normally used for engine cylinders. Its typically powered by an electric drill. Don't yell at me, it was just an idea ........ :uhoh3:

 

[LoganR]

I noticed with the sanding drums if you use too much speed it just polishes the glass and tears up the sand paper. Slower speeds seem to remove a lot more material and drums last longer.

 

[fishbox]

What about a dremel with a tile cutting bit?

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[Hawk72]

These work great for expanding existing holes.

https://www.dremel.com/en-us/Accessories/Pages/ProductDetail.aspx?pid=7123

 

[ca1ore]

I've been using 'cheap' ABS bulkheads for over two decades; haven't cracked one yet (though I did snap one off once). Sch80 bulkheads are unnecessary IMO. Using solvent welded slip versions avoids user error :lol:.

 

[fishbox]

This is what I've used http://m.homedepot.com/p/Rotozip-Tile-Cutter-Bit-XB-TC1/100349044

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[AZRippster]

Several years back I needed to expand the holes on a 180. I found some diamond sanding drums on ebay that worked with a Dremel. They worked fantastic and relatively fast.

 

[EagleFF]

I've been using 'cheap' ABS bulkheads for over two decades; haven't cracked one yet (though I did snap one off once). Sch80 bulkheads are unnecessary IMO. Using solvent welded slip versions avoids user error :lol:.

I have no doubt that ABS are good, just these particular bulkheads appear sub par, 10 wraps of 1 in Teflon and no tightness on connections,

 

[EagleFF]

Several years back I needed to expand the holes on a 180. I found some diamond sanding drums on ebay that worked with a Dremel. They worked fantastic and relatively fast.

I seen these and thought they would work great as the diamond tile saw removed material quickly with no chipping, but with sump refugium in place I had no room to maneuver or get good body position, my body is still paying the price

 

[EagleFF]

This is what I've used http://m.homedepot.com/p/Rotozip-Tile-Cutter-Bit-XB-TC1/100349044

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No issues with chip out?, I seen you post this bit in several places, but can't remember if you used the roto zip or dremel

 

[fishbox]

I used the dremel with this bit. No chips.

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[EnderG60]

As long as its not tempered just get the right size glass boring bit and redrill the holes.

You will need a drill press to keep it aligned since you wont have a small pilot hole or anything.

I did this on a 200g tank I got that I used for a sump. I redrilled the overflow holes for 2" bulkheads so I could drain it easily and fast.

 

[Reefer PT]

Wouldn't it just be better to get the schedule 40 slip bulkhead? No threat of cracking with glue. Plus much more likely to b leak free.


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[EagleFF]

Wouldn't it just be better to get the schedule 40 slip bulkhead? No threat of cracking with glue. Plus much more likely to b leak free.


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Simplified? yes, easier?, yes, but after having the sch 80 installed, connections are way better, tighter fit, and all around just a better suit for me, for what I already had, and have now, it doesn't take me long to give up on something that is not suiting my needs, or sub par, call it OCD, call it what you will, on any hobby I have done, I stay away from cheap and easy, its more work on me but a greater satisfaction after. I used to fly giant scale R/C planes, first one I built I used a lesser priced engine, granted when I got it running it ran fine, but it also cost me more in the long run to have support equipment for it, I paid the same price if I would have just bought the better engine, seeing as this is my first large drilled tank, its a learning curve on my part, if I have to ever buy another tank, I will know better next time.

 

[Reefer PT]

Sorry man, just a suggestion.


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[EagleFF]

Nothing ment by my previous post, I was just trying to convey my thinking,

 

[Bent]

I have no doubt that ABS are good, just these particular bulkheads appear sub par, 10 wraps of 1 in Teflon and no tightness on connections,

This right here is why they cracked.

PTFE tape is not meant for PVC threaded fittings. It's a lubricant for metal pipe. You have to use sealant paste. PTFE tape will crack the bulkhead just as you described.

It just seems like you are creating work here.

 

[fishbox]

This right here is why they cracked.

PTFE tape is not meant for PVC threaded fittings. It's a lubricant for metal pipe. You have to use sealant paste. PTFE tape will crack the bulkhead just as you described.

It just seems like you are creating work here.

I've never used anything on the threads of my previous 2 tanks. Are you suggesting to use this

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[ca1ore]

FWIW, over-taping a male Sch80 fitting will crack the female just as well as in SCh40 (personal experience :lol.