... One problem. The shutter now rotates in the hole. I don't see any sort
of pin that would stop that.
Most shutters for LF cameras have/had a small screw on the back that would
contact the lens board just beyond the hole. You would file a little groove in
the lens board to accommodate that screw. It was common, though, to remove the
screw (and then lose it).
... There are some tiny grooves on what I would call the jam nut (photo term
for it I don't know sorry) and its possible its just not tight enough. If I
need a tool, so be it, I need the tool.
The grooves on the jam nut are for a “spanner wrench”. Here’s one version on
Amazon:
https://www.amazon.com/Neewer-Professional-Stainless-Spanner-Opening/dp/B00J5F6ZI2/ref=sr_1_4?keywords=spanner+wrench+camera&qid=1556116471&s=gateway&sr=8-4
Someone (Copal?) made a now-adjustable wrench that would fit all of the common
sizes. (Flat piece of metal, more or less rectangular in shape, with
differently space teeth or ‘bits’ ground on each side)
Lens preferences are highly idiosyncratic. Your preferences in 35mm might be a
good indication of how you see photographically.
A 210mm lens is a good lens for learning large format. Most 210’s have enough
coverage that you don’t have to fret too much about tilting or raising the
front, and they give a comfortable perspective for a very wide range of
subjects.
If your 35mm preference runs to 35-45mm, you might do best to start with a
135mm large format lens with good coverage.
If your 35mm preference runs to 12-24mm, your going to be disappointed with
large format lenses that you can afford without mortgaging your future. Extreme
wide angle lenses are difficult to use on a Linhof III, in any event.
The only long lens I am happy to have is a 300mm Nikon-M f/9. I bought it
because at f22 it covers 8x10 well enough, but then discovered that it is
sometimes useful with 4x5 and 120 roll film for “details” like ice flow
patterns in a river. And it’s small enough to keep and carry.
Myron