Bulkhead hole size leeway?

[mloebl]

I'm looking at drilling a 1.5" bulkhead into my 75g tank, it requires a 2 5/8" hole. I can get a diamond tip hole saw bit to use cheap which is 70mm. If I do all the conversions right, it's about a 2.3mm difference which is less than a 1/10th of an inch. Is this too big of a gap or should I be ok? Not sure if it requires exactly 2 5/8" or there is some leeway for it. I'd take the tank to be drilled... but it's already all set up, so planning on draining it down 1/2 way then drilling a 1.5" hole and 1" hole for bulkheads.

Thanks,

-Mike

 

[NateHanson]

There's plenty of leeway with bulkheads. Probably even a 1/4" oversize wouldn't be a problem with a big bulkhead. That's just 1/8" on all sides, and the gasket and flange are usually 1/2" wide. Probably not a good idea to miss by that much, since it'll never stay centered though.

I don't think you'll have a problem being over by 1/10"

Nate

 

[mloebl]

Great, thanks! I just hope that the bit works... got it cheap on ebay, so thats the other thing that has me concerned. I'll see when I get it.

-Mike

 

[merk1_99]

Mike if you need help with the drilling let me know. I am getting ready to drill my 75 soon. So watching may teach me something.

 

[NateHanson]

Keep it slow and cool. A nice water bath if you're drilling horizontally is nice. I drilled a bunch of holes at about 200 rpm in a water bath, and the bit had just as much grit after 7 holes as it did at the begining. If you run it faster or hotter, I think you'll polish the grit off after just a couple holes.

 

[mloebl]

Merk1_99,

No problem, will let you know. I am still waiting on the bits to come in, from, lol, Hong Kong, so we'll see when it happens Just shipped today, though I did actually have something come in from Hong Kong once *before* a package from Winsconsin, so you never know...
I'm probably going to do some test drilling on some of my old tanks in the basement for practice. My only drill is a 14.4v cordless, so probably going to need to borrow my buddy's corded Dewalt for this.

Nate,

Thanks again for the tips! How long on average does it take per hole typically? IOW, how long will I be sweating out to see if I crack my tank and send the fish floor surfing

-Mike

 

[NateHanson]

How thick is the glass? We set it up on a drill press, with fairly light pressure, and slow speed. It took us about 20 minutes through 1/2" glass.

I've heard of people doing it by hand a good deal faster though. I suspect the bit life suffers in that case. It's a trade off between wearing out your bit and wearing out your arm.

 

[mloebl]

How thick is the glass? We set it up on a drill press, with fairly light pressure, and slow speed. It took us about 20 minutes through 1/2" glass.

I've heard of people doing it by hand a good deal faster though. I suspect the bit life suffers in that case. It's a trade off between wearing out your bit and wearing out your arm.

LOL! Thanks, I think

It's 3/8" or 1/2", hard to tell without measuring (75g aga.)

-Mike

 

[RichConley]

I bought one of those hong kong bits.

I drilled 2 holes in the back of my oceanic 58 (1/2" glass... tank is older than I am)

I drilled two holes in the bottom of my overflow boxes (made from 20L).

I drilled 2 holes in spare glass to get used to doing it.

My dad drilled a bunch of holes in the tile floor in the kitchen to have gas lines run for the new stove. The bit looks fine. I'm gonna cut holes in my sump in the next week or so.
Bit looked fine. These bits are a lot better than people make them out to be. Something being cheap doesnt mean its a piece of junk all the time.

I used a hand drill, and it took me maybe 10 minutes per hole once i got the hang of it. I clamped a piece of pine to the back side of the glass so that thered be no chance for a parcially cut out piece to snap off and chip the glass. I stopped when I hit wood. Keep the bit wet, and take your time. Its pretty easy.

 

[merk1_99]

If you can't clamp on wood put duct tape on the reverse side to prevent chipping....You are daring to drill it partially full makes it a little more tricky to keep the bit wet and cool.

 

[mloebl]

If you can't clamp on wood put duct tape on the reverse side to prevent chipping....You are daring to drill it partially full makes it a little more tricky to keep the bit wet and cool.

LOL or nuts I'm *very* nervous about it, but have read a few success stories. I know the glass sides are not tempered (which is good), as well as I heard draining at least 50% helps reduce the stresses. I'm hoping the fact it's thicker glass helps as may have a bit more resistance to cracking than your standard 10g tank thickness. Unfortunately don't have a choice unless I want to completely dismantle the tank.

-Mike

 

[NateHanson]

I think you'll be fine. I don't think the chances of breaking a larger tank while drilling are that great. Not that it doesn't make you worry, but I think you'll be fine.

 

[mloebl]

Got some of the smaller bits, just waiting for the larger bits. Hopefully USPS doesn't cram them into my mailbox again so I need scissors again to get it out of the mailbox . May try some test drilling this weekend with some of the older tanks just to get a feel for it. Very excited

-Mike