[PSUBS-MAILIST] Tapered Threads

["James Frankland" <james@guernseysubmarine.com>]

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