Measuring A Thread.

[Apache]

Crazy question, but how does one measure a thread?

I have a thread pitch gauge but unsure how I find the exact size (either metric or imperial)

I need to connect the Schrader valve to the airline and replace the badly made connector! I just need to find the correct adaptor.

Thanks

 

[steptoe]

thats a caliper ,

the pitch gauge I have/use actually has pitches in it and you set it on the thread,

have you a pic of your thread pitch thingie?

 

[Apache]

like this but less layers.

http://www.cdxetextbook.com/images/tapsDies_gauge.jpg

 

[steptoe]

thats like mine apache,

simply set it on the thread, there will only be one that is a perfect match,

be careful though that your pitch guage actually covers the type of thread you are trying to measure,

mine only does metric and standard imperial,

it wont do tapered threads etc that are often found on liquid/air lines etc.

 

[Apache]

some determined googling suggests it may be a 1/8" NPT Female thread.

 

[Elmer BeFuddled]

Def bsp. Set your vernier on imperial and whip out your zeus book. 1/4" bsp measures 0.518" OD. Pitch is 0.0526". Set the vernier to that and drop the internal ears into the thread and see if the points line up in the valleys of the thread. Also has 19 teeth per inch.

 

[Sidewinder]

I'd go for 1/8" too, but could be NPT or BSP.

Also they are not really interchangeable.

You should be checking the pitch.

NPT 27 tpi, BSP 28 tpi.

I hop, it's early!

 

[Elmer BeFuddled]

One I prepared earlier. 1/4" bsp.

 

[OnOff]

A good tip; get yourself a ZEUS book. A goldmine of engineering info. W H Smith USED to do them but any good tool shop should:

http://www.ebay.co.uk/itm/Zeus-Precision-Engineers-Metric-Data-Book-Charts-Reference-Tables-Drill-Tap-Size-/190580021532

With a vernier caliper you can measure the outside diameter of the thread and take a stab at the distance between teeth i.e. the thread pitch. A quick deko in the ZEUS book and you should have it. Don't forget some threads are TAPERED! As an aside I have some spares of these, your's if you want it:





This may help:

 

[SLIPSHOD & SLAPDASH]

I thought a thread was measured by how many posts & views it had.

 

[steptoe]

Ah, continuing from Onoff, I have both sides if you want to make a QR coupling up,

I got them while back to make an airline with and it was cheaper to buy a pack of 5 than it was to buy singles!

 

[Apache]

Going squinty trying to measure.

There may be a tiny taper or I may not be a whiz at engineering measuring!

external thread diameter is 0.648"

Pitch appears to be about 20 tpi, but with only 1/4" then it could easily be 19/21 tpi also

Have ordered the Zeuss book.

I have a man supposed to be ringing me

 

[OnOff]

Meant to say to measure across a few threads and divide by that number to get a more accurate idea rather than just across one........

The 13mm OD on your vernier in the OP is suggestive of a 1/4" thread though the loose fitting next to it looks bigger. Also your measurement of 0.648" and "19" tpi is suggestive of 3/8" fitting..................

PM me your address if you want one of mine anyway and I'll post.

 

[Apache]

Will LUK. Man still not bloody rang.

 

[Apache]

Man just rang. He is sending the bits I need to connect the Schrader valve to the oxygen line.

Thanks for the offers of help - really appreciated.

 

[kerching]

Didn't realise it was for oxygen

Does it come already oxygen clean?

oxygen has some nasty properties and really really does not like hydro carbon based grease.

I only mention this from my experience with mixing diving gases.

Also rubber O rings are a no go, even Viton is now seen as a problem as the gases emitted during a flash are carcinogenic.

Just mentioning.....

 

[Sidewinder]

I did not realise at the time it was for an O2 line either!

Patch you need to explain these things, I thought it was for a tyre inflater!

 

[kerching]

I did not realise at the time it was for an O2 line either!

Patch you need to explain these things, I thought it was for a tyre inflater!

Well if he uses the wrong grease then he will inflate more than just his tyres!Speaking as someone who has been on the wrong end of an Oxygen fire....bearing in mind that I am a Gas blending/ mixing Instructor, also Oxygen cleaning Instructor and factory trained diving equipment service technician! It can all go horribly wrong Fecking quickly.

Even a bit of lint whiz zing around in an empty cylinder when decanting oxygen in can cause ' quite a stir ' .......and NOT in a good or amusing way

Just being careful.......

 

[steptoe]

I did not realise at the time it was for an O2 line either!

Patch you need to explain these things, I thought it was for a tyre inflater!

I didnt think it was for a tyre inflater,

but I deffo didnt think it was for oxygen either,

I think the bits I have may be a tad unsuitable, even if they were remotely clean, even in the visible sense ,,,,,,,,,,,,

 

[Apache]

Sorry - it's to connect an anaesthetic machine to an oxygen cylinder. It is coming from the supplier of the anaesthetic machine (although the machine bought from another vet 2nd hand) so should be fit for use.

I was going to seal thread with PTFE.