Double tapping...

[K7BMG]

Ok so double tapping.

I have a brand new $800.00 137G tank, manufacturer calls it a 150, PFFFT. I hate that.

Anyway to my point, it has an internal overflow, the bottom glass has been pre drilled for two one inch lines.
Yes I can deal with that IF I have to, butt has anyone here ever drilled a bigger hole over the existing hole?
I want to install two inch and a half bulkheads.

I don't see a problem in doing this. Clearly the glass is not tempered or the existing holes would not be there.

So I thought I would ask and see if any R2R members or glass workers that may be reading this might have any advice or a reason this can't be done.
Thx in advance. YouTube failed on this subject, plenty of glass drilling videos just not cutting a second hole over the existing one.

 

[Jay Z]

A template with a raised edge to hold the bit steady would help. Mobile drill press would help to. I just double drilled a 10 last weekend.

Just make sure you don’t slip and catch the existing edge.

 

[K7BMG]

Yes I have the template, may only be able to enlarge one of them. They are close enough together that the 1.5 inch bulkheads will overlap. I guess I could trim the bulkheads, 1/8 inch on each one would do it.

 

[Jay Z]

Before you drill ask the manufacturer if the glass bottom was tempered after it was drilled. Just to cover all bases.

 

[K7BMG]

Sound advice thanks.

Second opinions anyone?

 

[Mastiffsrule]

Hello

The drilling doesn’t concern me as much as cutting bulkheads. How much would you cut off

 

[K7BMG]

Approximately 1/4 inch overall.
Keep in mind there is no pressure on these bulkheads.
They are at the bottom of the internal overflow. Very little if any head pressure on them.

 

[Darth.Daddy12]

Ok so double tapping.

I have a brand new $800.00 137G tank, manufacturer calls it a 150, PFFFT. I hate that.

Anyway to my point, it has an internal overflow, the bottom glass has been pre drilled for two one inch lines.
Yes I can deal with that IF I have to, butt has anyone here ever drilled a bigger hole over the existing hole?
I want to install two inch and a half bulkheads.

I don't see a problem in doing this. Clearly the glass is not tempered or the existing holes would not be there.

So I thought I would ask and see if any R2R members or glass workers that may be reading this might have any advice or a reason this can't be done.
Thx in advance. YouTube failed on this subject, plenty of glass drilling videos just not cutting a second hole over the existing one.

You can drill a larger hole over existing. You need to clamp down a template with right size adjusted how you wanna the new hole positioned based of the old one. You will have to drill it much slower then normal with less pressure. The key is to properly clamp the template piece so it can’t mkve or shift. I’ve done this 10k times in wood and metal working never once on glass however the basics are the same. In wood or metal when we drill the wrong size we no longer have the use of the pilot but to guid is.. in glass you’re already minus this part so it’s baskcally the same thing as drilling glass from the start.

Only part I would question is if it’s tempered or not. The bottom pre drilled glass of most tanks is tempered. There is a good way to tell using a light and looking for rainbow colors in the glass.. look up how to tell if glass is tempered using cell phone and I’m sure it will pop up.. I work with glass as a profession and will tell you this is 100% valid wat to tell. Light is distorted through tempered glass and not sgl pane plate.

 

[motortrendz]

I use modeling clay to hold the bit in place when I drill. I also use antifreeze to lubricate and cool the bit while I cut. Only thing you need to be cautious of is if they tempered the glass after they cut it.

I believe if you put a laptop behind the glass and use polarized sun glasses and turn them 90° you can see if its tempered bc the computer screen image will disappear.

 

[Mastiffsrule]

It wouldn’t be pressure so much as reducing the surface contact may unseat the seal a bit easier with an accidental bump

That said as long as you have enough seal it should be ok, but I would not try it.but that’s just me.

 

[K7BMG]

You can drill a larger hole over existing. You need to clamp down a template with right size adjusted how you wanna the new hole positioned based of the old one. You will have to drill it much slower then normal with less pressure. The key is to properly clamp the template piece so it can’t mkve or shift. I’ve done this 10k times in wood and metal working never once on glass however the basics are the same. In wood or metal when we drill the wrong size we no longer have the use of the pilot but to guid is.. in glass you’re already minus this part so it’s baskcally the same thing as drilling glass from the start.

Glass hole saws require templates or a mobile press as they do not have pilot bits.
I have watched a guy free hand on YouTube, no thanks I am NOT that steady. LoL...

 

[Darth.Daddy12]

Glass hole saws require templates or a mobile press as they do not have pilot bits.
I have watched a guy free hand on YouTube, no thanks I am NOT that steady. LoL...

This is my point it’s no different then normal as the lack of a pilot bit makes having an already drilled hole not any more issue then drilling from scratch. Worst case you just need to make sure your template is fresh and properly clamped down.

 

[Darth.Daddy12]

This is my point it’s no different then normal as the lack of a pilot bit makes having an already drilled hole not any more issue then drilling from scratch. Worst case you just need to make sure your template is fresh and properly clamped down.

By fresh I mean new and I used before as the hole will widen slightly over use. A new template is spot on and won’t allow bit to stray.

 

[K7BMG]

This is my point it’s no different then normal as the lack of a pilot bit makes having an already drilled hole not any more issue then drilling from scratch.

Yup I agree with you... Just don't want to lose an $800.00 tank because I was afraid to ask a
question, and get some insight.

 

[Jay Z]

Depending what bits he has he could run it with a pilot bit and a piece of wood clamped behind it. Existing holes.

 

[motortrendz]

Glass bits dont have pilots. They're cups. If us use modeling clay make a circle and use the cup to imprint where the ne whole will be, fill it with a drop of antifreeze and then us the imprint as your guide to drill your new hole. Itll keep the pit in place and it wont walk as well as hold in the lubricant. Also put tape across the inside of the glass to prevent it from cracking when you drill through it. Itll also prevent the cut piece of glass from falling into the tank and cracking the glass

 

[K7BMG]

The glass bit was bought from BRS, I bought a matching wood hole saw for the template making.
Had to sand the template lightly for the glass hole saw to be able to rotate inside.
So there should be no wobbling or going out of round unless the clamps fail to hold the template in place.

 

[K7BMG]

Be back in a bit, the wife has dinner ready.
Thanks for all the advice everyone.

FYI She made chilly.

 

[Jay Z]

Glass bits dont have pilots. They're cups.

My bosch’s are pilot bit capable and I know Milwaukee make pilot capable diamond cups too.

 

[Mastiffsrule]

Be back in a bit, the wife has dinner ready.
Thanks for all the advice everyone.

FYI She made chilly.

Beans or no beans?