fitting
This fitting for a pressure washer seems to be straight-threaded. The OD of the threaded portion is 16.18mm according to my caliper. Thread pitch is approximately 1.5mm. I need to convert this to NPT.
I first thought of ORB, but it doesn't appear to be the right type. Based on prior history with this vendor, there's a chance its a German DIN fitting. But I don't know enough about those to make a good ID.
Just to add some visuals to the others' explanations using your photo, you need to (1) push on the collar trying to move it parallel to the tube, and (2) pull the tube.
To reconnect, push the tube into the collar until it stops (should be about 1 inch). Make sure the tube end is square (perpendicular to the tube axis, with no damage); cut a bit of the tube if necessary.
Swagelok fittings are different than compression fittings and will not work. Both are very different than flare fittings, which have a tapered nut and require the tubing to be formed in a "flared" taper at the end (using a special tool) and do not use a sleeve (ferrule). They also use a different thread:
You may find that regular compression fittings are labeled "tube" fitting in your locale. Home Depot Canada has them, they include a brass insert (for plastic tubing) and ferrule (for all tubing applications; for your purpose do not use them.
Why don't you take your connectors down to the local mom & pop plumbing / hardware shop instead of going to the "big box", they likely have the part and will be full of good advice as well.
here's the link to the part at HD: 3/8 comp. x 3/4 mip adapter
Best Answer
It appears to be a 1/2" threaded stop plug with an Allen wrench shaped hole in it . It also looks like the plumbing fitting itself may be 3/4" itself , with a 3/4" to 1/2" reducer in it.
The fitting, the way you hold it in the picture does give us a shot of the other side of it... Would need to see that too.