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shrader valve threads

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shrader valve threads

Unread postAuthor: john bunsenburner » Sun Dec 06, 2009 11:23 am

Well, after looking over the net I found that my schrader valves, assuming they are not from the UK have the following threads on them:

7.7 mm OD, thread root diameter is 6.9 mm x 0.794 mm pitch

As i have a free source of these i would like to find a way to use them (for cartridges), the problem is that threading the stem renders the entire valve useless, the walls are simply too thin for either a m5 or m6 thread, while the diameter is too small to allow for m7 threads.

Now where do you think i could find a tap that would cut the internal threads with the previously mentioned measurements.

I guess if worst comes to worst i either insert the valve stems into molten metal that is then threaded and screwed in somewhere, or I try and make a tap on my lathe, but i would rather avoid those two possibilities.

Thanks in advance for your help and happy spudding!
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Unread postAuthor: psycix » Sun Dec 06, 2009 11:34 am

The easiest way to do this is to simply glue them into a hole using epoxy.


Depending on what kind of material you want to tap the threads in, maybe you could build a tap out of a shrader casing, by milling slots into the threads and slightly tapering them. I think it should be able to tap PVC if done properly.
Then you can cut M10 threads on the PVC cylinder with internal shrader threads.
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Unread postAuthor: potatoflinger » Sun Dec 06, 2009 11:48 am

I have one of these It has a tap and a die for all of the threads on a schrader valve. I think the one I bought was less than 5 dollars at a local sporting goods store.
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Unread postAuthor: john bunsenburner » Sun Dec 06, 2009 11:55 am

I want to tap into metal and have it safe to 600psi so i have a safety factor of 3.

Flinger,

what you have looks good. What is it used for? It seems like the outer threads this thing cuts, are the same size as the INNER ones i need to make. I am guessing this is used to make, or remake, shraders, or similar valves, to accept shrader cores and caps, and the likes. I need the opposite, a tap that lets components accept shraders.
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Unread postAuthor: Gippeto » Sun Dec 06, 2009 2:54 pm

John, are you trying to make something like this?

http://www.spudfiles.com/spud_wiki/inde ... ader_valve
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Unread postAuthor: john bunsenburner » Sun Dec 06, 2009 3:54 pm

No, i have a normal schrader valve, and i need to screw it in somewhere, and so i need a tap to thread a hole into which it will screw. The treads are a wierd size and so i am asking if there are any taps that will do the job.
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Unread postAuthor: dewey-1 » Sun Dec 06, 2009 4:07 pm

The closest tap size is American NEF 5/16-32.

The OD on a typical Schrader valve threads is .305" at 32 TPI (threads per inch)

5/16 = .3125 inch. The difference will be .3125-.3050=.0075 inch.

That is the closest tap size I have found so far. I am sure that would be within the tolerance limit for your use. You will have to use some liquid thread lock like Loctite for a good pressure seal.
Hope this helps!

McMaster Carr Taps:
Tap Material High-Speed Steel
Surface Coating/Treatment Uncoated (Bright Finish)
Thread Type NEF (National Extra Fine)
Inch Size 5/16"-32
Single Taps NEF
Thread Direction Right-Hand Thread
Thread Length 1-1/8"
Overall Length 2-23/32"
Pitch Diameter Limit H3
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Last edited by dewey-1 on Sun Dec 06, 2009 4:33 pm, edited 3 times in total.
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Unread postAuthor: rp181 » Sun Dec 06, 2009 4:07 pm

in plastic you could probably dill a hole, and thread it with a schrader.
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Unread postAuthor: john bunsenburner » Sun Dec 06, 2009 4:29 pm

Hmm, american taps in Europe..gulp...

You know what, i'll make calls tomorrow and get in touch with the local schrader producer, maybe i can get my self a real HSS tap with these specs...

Anyone found the correct tap for this job?
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Unread postAuthor: psycix » Sun Dec 06, 2009 4:46 pm

Gippeto wrote:John, are you trying to make something like this?

http://www.spudfiles.com/spud_wiki/inde ... ader_valve

BCarms carried those.
I have a few of them (very unreliable shop though, and its down now)
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Unread postAuthor: dewey-1 » Sun Dec 06, 2009 5:31 pm

john bunsenburner wrote:Hmm, american taps in Europe..gulp...

You know what, i'll make calls tomorrow and get in touch with the local schrader producer, maybe i can get my self a real HSS tap with these specs...

Anyone found the correct tap for this job?


Here are taps in Switzerland ebay. No idea if UNEF or otherwise.

http://shop.ebay.ch/?_from=R40&_trksid= ... Categories
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Unread postAuthor: c11man » Sun Dec 06, 2009 7:55 pm

i dont know its right or not but they might be 1/16 npt
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Re: shrader valve threads

Unread postAuthor: Gippeto » Sun Dec 06, 2009 11:39 pm

john bunsenburner wrote:I guess if worst comes to worst i either insert the valve stems into molten metal that is then threaded and screwed in somewhere, !


John, what you're describing here...is what I linked you to. Will it work or won't it?

How about a picture to clarify what exactly you're trying to do?
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Re: shrader valve threads

Unread postAuthor: Heimo » Mon Dec 07, 2009 5:54 am

john bunsenburner wrote:
1 As i have a free source of these i would like to find a way to use them (for cartridges), the problem is that threading the stem renders the entire valve useless, the walls are simply too thin for either a m5 or m6 thread, while the diameter is too small to allow for m7 threads.

2 Now where do you think i could find a tap that would cut the internal threads with the previously mentioned measurements.

3 I guess if worst comes to worst i either insert the valve stems into molten metal that is then threaded and screwed in somewhere,!


1 what kind of m6 thread did you use there are two common types the M6X1 and M6X0.75
I have also found that the M6X1 cuts the threads too deep and renders the valve useless but the M6X0.75 worked pretty good in the past for me

I attached a pic of my experiment to determine what thread size would work. I had to look for myself and my conclusion was that the M6X0.75 would do for the valve and the M6X1 cuts almost through the casing. So I think the M6X0.75 would work fine except maybe in very high pressure situations

2 you would most likely find that tap in a specialty tool store

3 what metal do you plan to use? aluminum wont work copper based alloys dissolves quickly in aluminum and lead is too soft tin would solder itself onto the valve in general I would say this is a bad Idea

there is another option

you can sleeve the valve in a metal tube just fitting over the valve then lock the valve in place using epoxy or you can solder it in place or braze it if you remove the guts of the valve first
then you can cut threads into the tube without worrying about the strength of the valve
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Attachments
Photo 0327.jpg
threaded with M6X1 be sure to use the M6x0.75 thread it does not cut as deep as the M6x1 thread
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Unread postAuthor: kenbo0422 » Mon Dec 07, 2009 7:04 am

If you can cut threads with a lathe, just cut extra fine threads that won't weaken the sides of the valve. A tap can be made by cutting a piece of steel with the same dimensions and thread needed then slotting it down the sides. Heat it up and cool it down fast to harden it and you have a homemade tap.

Use that lathe!
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