DPN

I can't seem to find the thread size/pitch for the valve cap threads on a Presta valve.

Has anyone ever run across this dimension? I'm not referring to the threaded stem itself...just the end of the stem where the cap screws onto...

I'm making a CO2 inflator and need the right info...

Thanks,

DPN

HDFACTORYCERTIF

With just a thread pitch gage, it appears the threads are 1mm pitch with a 5mm outside thread diameter. I cant find a spare tube, or I would have put it on a optical comparator.

Zouf

OP: "valve cap threads". Not stem.

Al1943

Good point!

DPN

That's what I was getting, too.

Is there such an animal? I have a M5 X .8 tap and die, but can't find a M5 X 1...

Thanks,

DPN

HDFACTORYCERTIF

Thats is a very coarse thread for such a small diameter. It is a special thread and not standard. My search of industrial vendors we use came up empty.
A custom tap can be ordered, but could cost $100, since it is so small with the coarse thread. A female thread would be hard to cut on a lathe but not impossible.
If you have a lathe available, a simple tap can be made of drill rod, then heat treated.
A school shop may do this for you.

HillRider

The CO2 inflators I have (and floor and frame pump heads also) don't thread onto the valve stem, they grasp it with a rubber washer or gasket that's either a tight friction fit or compressed around the outside of the valve stem to form a seal.

rmfnla

Presta > schrader adaptors use this thread, too, so it must have some sort of tooling available.

HDFACTORYCERTIF

The Campy end on my old Silca pump uses a compressed rubber seal, that may be alot better way to go.
If I were to do a production run of such an item, purchasing or making taps would be economical, for a one off part, it would take a few hours to make a tap,or, a couple of hours to get it done in a lathe.

m100

It's long time since this thread was active but having failed to find a reliable source online I gave up and measured one. They are NOT metric!

0.2305" for the stem, threaded 32 tpi
0.2030" for the cap threaded 24 tpi

The thread form also looks like 55 deg not 60 deg

krome

#12-24tpi works.

I use a 12-24 screw to keep the inflater adapter on my bike. It is an extra long fender bolt, the little brass schader adapter screws onto it.

#12 doesn't match the spec m100 gives. The basic diameter for a 12-24 thread is .216". Don't know what the "standard" is, but I think that 12-24 is your best bet.

12-24 is kinda oddball, but available.

Paul Koning

It's 12-24. Not M5x1.

I just made an adapter. For a template I used one I had lying around, an old Dutch Presta to Dunlop adapter. Both that adapter and the Presta valves on my tires (Hutchinson) measure .207 inches, which is well above what M5 would be but a hair below the nominal size for #12. Slightly under is believable (wear and/or low grade work); over isn't.

Also, the adapter I had comes with a rather long threaded section. It perfectly fits a #12x24 screw without any binding. So I threaded my new adapter #12x24 and it fits nicely.

FWIW, #12x24 taps (and, for that matter, M5x1 taps) are readily available by mail order, for example from Enco.

mfrassica

Hello,
Can you please help, I am trying to find out the internal thread that accepts a replacable presta valve core. This is not the external threads on the valve stem or for the small cap. These are the threads that are on the inside of the stem that mate with the approx 6 external threads on the presta valve core.

I just assumed they were metric but a M4.5X.75 and M4.5X.5 do not work. It measures 4.6mm on the OD of the external threads. Any help would be great! I've asked all sorts of people and they all point back to this one thread on the web.

Just Riding

I looked at 2 presta valve cores that I had, and the external diameters measured about 4.50 to 4.55mm.

I'm pretty sure the thread pitch is 40 threads per inch (tpi), checked with a pitch gauge. This is equivalent to a pitch of about .63mm. I checked with a metric pitch gauge and neither 0.60mm or 0.65mm seemed to fit. The thread at the top of the valve core is 24 tpi, and the thread on the outside of the stem is 32 tpi, so it seems reasonable that the valve core thread is an inch based thread too.

I noticed that the thread form doesn't appear to be a standard 60 degree "V" thread. Instead it looks more like a "U"; skinny, almost vertical threads with a wide space between them.

It wouldn't surprise me if this particular thread is unique to presta valves and used on nothing else. It may be that the tooling is custom made for a small number of manufacturers, and there may only be a handful of people that can give a definitive answer to your question.

joeminglin

Any luck finding a tap?

fietsbob

Happens to be, a non threaded band between 2 different thread sizes & types is a common machine practise ..

It the case of Presta valve stems that smooth band is where the Silca pump head gasket seals best..