Well it is fairly simple. I have a Bong Vodka bottle that I am going to turn into a bong. Usually I just wing it when making a bong but this bottle is a little expensive so I am being cautious. I have measured the down stem and it was ... 17/30" which is .56" Or rather it was that measurement with the grommet, the down stem it's self was 1/2" So the question becomes -> What size should I drill my hole? I have to buy a Diamond Bit to get this done obviously and I have researched the techniques to drill glass efficiently and I have plenty of practice bottle to play with. Everything is in mm when looking at the bits, .56" translates into 14.224mm. So should I get a 14mm bit? 13mm bit (which is .51")? I know everything is going to fit snug and the grommet with flex as you push the glass down stem in there and everything. So will 14mm be my answer it will still be smaller than the thing so everything should fit real snug yes?
yea bro id say get a lil bigger than 14mm cuz ur gona have to use a rubber stopper. maybe go for the 18mm one n then plug in the hwole wit the stopper n down stem?
I did this with a milk bottle a while ago. I bought a glass bit at home depot. It is made by Ridgid. It has a hollow center, like a cylinder shape, with grit on the cutting edge. Cuts amazingly fast and leaves a nice smooth hole. I think I used the 1/2" size. I did have to make the hole slightly bigger after so I used a grinding bit on a drill. The bit was made for sharpening steel, but if you keep running water over it (as you should) it won't get clogged. Go slow and good luck.
If I get an 18mm that will be over 3.8mm too big, the 15mm is bigger than the 14mm and goes over the size of the grommet and the downstem. Yes Goggle is my friend but so is GC hence why I came here where people actually do this kind of activity more often. Instead of the over large amount of search terms I get from the vague search terms I can use to get my answer. You can't explain something to a search bar. That is an interesting looking one. Thank you for that, I do know what kind of bit to get a Diamond Core drill bit which is essentially a hole saw. If I have to make the hole bigger than 14mm I may just get a rotary tool and chip away slowly on the sides. How did the milk bottle one come out? I have already investigated the techniques and methods on youtube and similar so I just needed to figure out the bit size that would work best for the application. 1/2" is the size of the downstem alone so that wouldn't work here, gotta put that grommet in there glass on glass never ends well. We will see when I am done.