The PLM2000 software comes with a DOS program called SPLIT.EXE for chunking up large NC files based on how many lines you want. Default is 1000 lines per chunk.

It appends a digit, beginning with 1, to the end of the name for each chunk. For example CUTIT.NC becomes CUTIT1.NC CUTIT2.NC etc.

It also appends a couple of lines to the end of each chunk. At the end of CUTIT1.NC would be

M20
CUTIT2.NC

Very simple for the PLM2000 software to load the next chunk and continue. That could be added manually without much bother.

Why a splitter for x64 Windows? Because it doesn't support running DOS software at all and rebooting the computer running the mill into Windows XP just to split a modified NC file is a PITA due to having to re-zero the mill before quitting. It has incremental encoders and resets to 0,0,0 when running the control software. Would be nice to split a changed file then sneakernet to the mill computer, without having to exit the PLM2000 software.