[Arran]

Terry;
  I did something similar to replace tips on a soldering gun, the tips that Weller used seem to break off near the end thanks to that square material they made them out of. I think 10 guage is the stuff that fits. Then I have a Taiwan cheapie gun that I bought over 20 years ago, and whilst it is lower wattage then the Wellers I have it still has it's original tip so whoever designed that tip did a better job then Weller did. I think I have one of their pencil irons someplace, if got tossed aside after the tip broke off, right across the threads, after Cooper took over the quality really went to pot, it has improved since.
Regards
Arran

[Radioroslyn]

Yup the Weller guns have gotten more cheaply made over the 20yrs or so. When I was looking for a hi power gun the newer Weller had a lot complaints about the quality and the set screw style of tip mounting need constant attention . The older ones use nuts to hold the tip on and only need a little tweak every once in a while w/ a wrench. The D-550 I got I think maybe one of the last of the old style large gun. It was replaced by the D-440 which is less power and poorer overseas quality.

[35Z5]

AFAIK the D440 that uses same tip as 8200 were discontinued in the '70s, never seen one of those with tip retaining screws. I have a couple, are considered ancient by today's std.  

Both a D550 & D650 are available but have tip retaining screws.  Modern 550 have similar wattage to 440 & 650 is similar to old 550. Both use the large tips. Their tip retaining does have a "beefed" ring but IMO the nuts were still far better.

I have what's probably a early/mid 1960s D550 rated 240/325 watt. Picked it up at a junk shop for $15, was barely used.

[codefox1]

Yeah, the old ones were better, yours is missing the trim screws. Curiously the shells are interchangeable, bought an old one surplus with a bad coil but good body to fix my 6 0+ old blaster.

[Radioroslyn]

Both of the Weller guns I have had the brass sockets for the penlite bulbs cracked. Easy fix.