"Sonny" wrote:

Almost all of my air couplings leak lots of air. I bought them from
Harbor Freight and Home Depot. Is there any way to tight them, so
that sir doesn't leak?

There was a time in my career when I designed quick connect couplings.

Based on that experience, will offer the following:

1) Plugs need to be case hardened to minimize scratches.

Case hardening costs money which is easy to skimp on without being
easily detected.

2) Very accurate screw machine tolerances are required to maintain the
seal between plug and coupling socket.

Sloppy machining works for a little while, sometimes.

You can try replacing the O-Ring in the coupling, it may buy you some
time.

Plan "B":

Scrap them out and start over.

Lew