With knobs on!

The machine screws arrived, and little gems they are! All freshly machined edges and bright brass. The screw threads fitted as expected but the heads were too large for the opening in the handles so two of them were filed down with a flat needle file. Everything went together neatly but at 0.5" the screws were a little too long to be fastened tight onto the spindle. They were left flush at either side of the opening as this looks neatest. If they become loose I'll trim them down, which is probably simpler than making a collar to keep them at the preferred height (don't have any brass tube stock to hand).

JOB DONE