RE: [PSUBS-MAILIST] Tapered Threads

["Emile van Essen" <emile@airesearch.nl>]

Hi James ,

There are tables for minimal drilling and tapping depth for BSPT or NPT.
For stainless drill 0,1- o,2 bigger.

No washer! Thread is intended to seal without loctite.

I also dislike taper threads....

All the best, Emile

-----Oorspronkelijk bericht-----
Van: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] Namens James Frankland
Verzonden: zondag 19 oktober 2008 12:18
Aan: personal_submersibles@psubs.org
Onderwerp: [PSUBS-MAILIST] Tapered Threads

Hi All.

Can anyone help me with this minor thing.

I'm making the VBT and i had the threads cut on a special threading machine.
See this picture.

http://guernseysubmarine.wordpress.com/

Anyway, the 1 inch valve has a tapered thread, so i have cut the thread on
the pipe accordingly to have the same taper.  It fits perfect and will screw
up nice and tight.  

But, the little 1/2 inch swagelok fitting has a straight thread inside.  So
i cut one end of the pipe tapered thread and the other straight.  Im not
sure which to use.  If i screw on the tapered thread, it will tighten up but
i'm nto sure if thats right as i feel its only tightening on the end of the
taper.  But if i use the straight thread, it screws down right to the end
and is it going to seal properly?  I feel as if there should be a rubber or
fibre washer in the end of the swagelok fitting to seal the straight thread.
There isnt one but i can make one easy enough.  

Any ideas?  Taper or non taper.  Washer? 

Thanks
James


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