Thread specification for perfume bottle neck

Can't the people who supplied the bottle, or the manufacturer give you the spec.
Or are you dealing with 'non engineers' .

Del

Yes!I am dealing with 'non engineers'.

Yes.. you have to be firm with them and
s p e a k
s l o w l y

Take a shdow graph or paper template and get the supplier to sign it off.

The thread may be a special, deliberately made, so that nothing else will fit, unless you make new tooling to match it.

I needed a shallow thread for a cap on a regularly used pressure test cell with aluminium male and plastic female parts that couldnt be cross threaded. After many prototypes I ended up with a trapezoidal thread M66 by 6 pitch which works succesfully for many thousands of test cells. We also designed an M36 by 4 rounded profile thread for a chemical bottle because all the threads and seals offered by bottle manufacturers leaked under pressure.

So there is nothing to stop you designing your own thread. Whitworth doesn't have the monopoly on thread design!

Somewhere there is an engineer and a toolmaker who designed and built the tooling to make those threads. Find either of them and you will get your answer. Failing that, I would just copy the thread size and form to make the cap.

If you are buying a large quanity, have the bottles threaded to your spectications!

Hello Craftsmen,

I can relate to your problem of an uncommon thread design.

There are self sealing threads, generally, in the US they are of the NPT (National Pipe Taper) variety. This is just an example of a sealing thread. Machined NPT threads can seal without the need for teflon tape (if they were made properly). This likely has some relation to what you are looking for, however here we are talking about machined components. The special tapered design will cause the thread gaps to close up completely when tightened, effectively sealing. These threads can be purchased from any hardware store to get an idea og the tapered design. If a thread like that is made well it should seal. It seems that for your application you need a combination of a rounded thread, which is tapered. I am not sure if there is such a thread, as a standard, if there isn`t, I'll be the inventor. I have previously designed special rounded threads, and a taper can also be designed, relatively easily. What really takes the time is to take all your tolerances into consideration, therefore you must know the manufacturing processes used to make both mating parts. A machined component will have a different way to establish tolerances as a plastic component, typically made by an injection mould,as shrinkages and mold type are important. Now you also need to look at the volume of production. Injection moulds start to make sense with cold runner and hot runner moulds at different production quntities and price levels, as well as split moulds and moulds with rotational inserts. Rotational inserts allow for plastic thread manufacture without a split line, usually caused by two mould halves on external threads. The core insert is threaded out of the component after injection and initial cooling. If your intention is to only make a few hundert parts then consider rapid prototyping machine components followed by prototype tooling.

Back to the thread design, it can be fairly complex. First measure the existig thread, If you do not have a shadow graph at your disposal, it is possible to get create a simple drawing by using a good quality caliper. In the imperial system you need to measure to three decimal places for a simlified design. Measure the following on an outer thread: Full overall diameter, crest to crest, diamter of the round thread lobe, Pitch, crest to crest, or to equal features of the thread. You will also need to measure the inner diameter, overall. To measure an internal thread, you need to cut it in half to properly see it, the same measurements will apply.

Once you got your numbers, get someone to draw it up, manually at 10X scale, better on a 2D Cad system, 3D CAD if you want to get fancy, and have the software capabilities to deal with the complex geometry. Apply the production tolerances as min and max clearances between the two mating threads. It seems that for your application you may want to consider a multiple start thread, and seling washer, This thread should allow for non cross threading, and a quick ~ 1/3 turn to tighten, however you`ll need a way to seal it, as the thread is not suited well for that.

Please e-mail me direct if you need more help - mircog@canstampconsulting.com

Aluminum for perfume? odd choice for that market.

The thread could be GCMI -425 thread. This is a tight TPI configuration it may be work checking out. The glass makers have all of thier "standard" finishes on line for you.

your bottle supplier has to be able to tell you the thread config. I would not trust them as a supplier if they cannot tell you something as simple as what cap works with their bottle.

Are you in the states? If so, try using a distributor for the first order or two. They will work with you to make a good combination with appropriate closure. If you are in Europe, try GIBO. They are located in Milan. The owner is Giani Bocola, a family friend. In the states try Tricor-Braun. They bought my family business a few years ago. When the took over our engineering and design department, they got the best in the packaging industry.

Thanks Guys!!I Can now solve my problem with the directions provided by you all.And by the way,SGQ,The aluminium bottle is coated with a lac·quer like coat.Perhaps that is because they are using aluminium for a perfume bottle.