I did a search for info on threading on that block (haven't seen it, but up to now all DD blocks I
have seen have been 1/4 NPT.
From the comments in
this thread they might be 3/8 NPT or even 3/8 BSPP.
Here's a picture of two of 'em stacked
Notice the o-ring under the adapter flange? Sort'a looks like a parallel fitting to me - makes sense, given that it's in plastic.
I think I'd better retire as "expert" - clearly I don't know enough about this block...
Anybody else have one in-hand?
Failing that, mmmmalas - can you unfasten a fitting and measure the opening of the hole? that'll at least settle the issue of 1/4 vs 3/8 (and no, 1/4 fittings are not 1/4 across).