Hi John,
Nice door knobs, did you make them your selve?
Regs Maarten
G'day Maarten, I had some thick brass pins that had a head that is approx 2.5mm across and these are what I used, see pics below,

I had blackened them for another job I was doing,

So I used some fine sandpaper and took the blackening off,

Side view,
thanks for looking in,
best regards John.