Take-up spool.

Take-up spool cylinder is from plastic rainwater down-pipe, I've made ends of white faced Formica glued to hardwood disc inserts.  A similar insert in the middle of the cylinder holds the 3mm dia. brass rod 'hook' on to which the start of the music roll is fastened.  A piece of 12mm diameter brass rod, inserted into the end hardwood disc, is drilled and tapped through its diameter to take a grub-screw for locking spool to spindle.

The original take-up spool hook was made as in the picture above and was quite OK for the paper rolls I had punched myself.  However, after buying some pre-punched music rolls I found it necessary to modify the take-up spool as shown in the picture below.  The simple round hole in the upper picture did not allow the roll end tag to hook on satisfactorily.  The diameter of the spool is not important.  However, the larger it is the more constant will be the speed of the music over the tracker-bar.  Grinders tend to keep the music tempo constant by instinctively reducing the speed of turning the crank-handle.