On Sat, 25 Apr 2020 11:24:57 -0700 (PDT), Molly Brown
wrote:

The 7250AN acorn tip nuts used by the Weller D550 professional soldering gun are badly designed and will not produce good contact and will prevent the tip from getting hot.
BS. They've been working fine for about 40 years.Or more. CXan't
remember when I got my first one -and they are a lot better than the
old WEN soldering guns that used a pair of scresws tomake the contact.