Bottle Tap

8 TPI, 1" min diameter, 1.08" max diameter. The thread form is rounded like an acme thread although I don't know if it's exactly the same.

For backyard-type experiments, the most common method to attach plumbing is to drill the hole in a bottlecap and put a Schrader (tire) valve in there. From there you can adapt to whatever you want.

Tim.

Thanks for the info, Tim, but what I want to do is screw a glass bottle into a plastic manifold. I want to know if I can buy a tap to tap the hole, or do the threads have to be cut manually on a lathe?

Mark

You know, making silencers can get you in big trouble. The two liter bottle works quite well for handguns up to .38 cal. but tends to blow off of high power rifles. Good luck.

He's talking about a glass bottle, so while your guess wasn't a bad one with the information you had, it's probably no the case here, given the new details.

Nothing nefarious intended - it's for a piece of medical equipment to be used in Veterinary medicine. I'm not going to actually use a soda bottle, but I will (might) be using a bottle with the same thread.

Mark

I am not a bottling expert, but my impression is that a glass bottle threading into an aluminum threaded hole will not seal at all.

The seal on most bottle caps depends on the top of the bottle pushing up against the inside of the cap. In an aluminum manifold hole cut with a tap, you won't have anything to push up against and seal. If you put in a backing plate with hole in after tapping the hole and have a rubber/plastic seal, it might work. But really, all applicatins I see doing this just drill a hole in a regular plastic bottlecap and put a tire valve in.

The bottlecap thread does not taper like a usual pipe thread, so the thread itself provides no seal. The thread just provides the pressure to form the seal at the top of the bottle opening.

Tim.

How about using a garden-hose thread rather than a soda bottle thread? Those gaskets are _really_ cheap and effective for both pressure and, I'd imagine, suction. Fittings can be bought at any decent hardware store as well, for either side of the connection.

Another thought - maybe googling for home brewing supplies might give you a convenient place to buy what you're looking for?

Dave Hinz

I suggest using a threaded insert in the manifold, held by epoxy. If you want something more rugged than a used bottle cap, shop for some of those screw-on plant watering attachments.

In fact, I have used garden-hose gaskets for some backyard experiments with soda bottles. They are pretty much an exact fit.

(One such experiment is to fill the bottom half inch or so of the soda bottle with liquid nitrogen, screw a pressure gauge and seal on the top, and then run away and watch the pressure gauge with binoculars to determine the pressure at which the bottle explodes (circa 150 PSI). I think I documented these experiments back in the 90's, probably on this same newsgroup!)

I think the thread diameters are very similar, but a soda bottle is

8TPI vs a garden hose's 11.5TPI.

Tim.

I kind of thought they might be, but I'm not near a garden hose at the moment.

Seems like a not-very-good fit from here?

Certainly the threads don't mesh. But the gaskets seem fine. (I might have had to whittle away the edge of the garden hose gasket to get it to fit my bottle-top plumbing, but maybe not! IIRC a knife was already in use for adapting the pressure gauge to the bottle top.)

I think a tap might be hard to find, but it's easy to make a bottle cap on a lathe. Use Delryn (an acetyl engineering plastic) rod as rawstock. I do it by hand rather than under power.

I think the threadform is closer to half-round than V or Acme. It is on PET (plastic) bottles. I don't have a glass bottle to look at.

That's what I like. A detailed and precise specification!

Tom

Mark,

To the best of my knowledge, you won't find a tap for a bottle cap. Bottles are made with the thread molded of course. The caps, if metal, have the threads rolled into them using very sophisticated equipment and involving several operations. I 'believe' plastic caps are again molded with the threads.

Each manufacturer of the bottle/cap combination has their own thread specifications, some of which are 'standard' to the industry.

Can you drill out an oversize hole and epoxy in a plastic bottle cap to receive the bottle?

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

Probably easier to make a tap on the lathe then cut the threads into plastic.

I did some research on this and found this site:

Most of the documents are available as free pdf downloads, look at: catalog number AU-124 if my memory serves...