G'day folks,
mikoooo, that's a pretty curly question, as it happens! I'd say that there are two possibilities here.
One is that the ends of the roller spindle were originally just a slip fit in the cast iron end brackets. This would rely on the bracket bolts being kept tight, to keep everything together.
The other is, as you say, that the brackets are screwed on to the spindle. If the spindle holes in the brackets are bored through [i.e. the ends of the spindle are visible], then they are screw fitted for sure. If not, they most likely aren't.
In either case, it can be said that the joints will be thoroughly rust-bound [from the spindle condition], and will take some work to separate, if it can be done. It may be necessary to cut the spindle, and drill the stub ends out of the brackets.
To start with, apply a good penetrating lubricant [e.g. CRC 5-56, Inox, Penetrene for example - not WD-40] and give it a week or so to soak in. Then apply heat to the bracket with a hot air gun or propane torch, with the spindle held in a vise [soft jaw covers are a good idea], and try to 'unscrew' a bracket, using leather gloves. Avoid impact on the brackets, and the use of lever extensions - cast iron is brittle.
