Attached is a tool (excel spreadsheet) that I've been putting together to compute hole size and locations for the Nipkow disk.
One supplies:
* The disk radius
* The number of lines
* The aspect ratio
* Frame position
* Desired hole overlap
From this, the spreadsheet calculates the maximum (round) hole size, and location of the various holes. Location is expressed both in polar and cartesian coordinates. I have fashioned a homemade micrometer which I will use in conjunction with the polar coordinates to locate the holes on my disks. If one has access to a machine shop, particularly with CNC capabilities, the cartesian coordinates may be more useful.
Also included is an American drill bit table, to cross-reference decimal hole values to their standard bit-size equivalents.
Let me know if you find this useful.
Pete
AC7ZL