hiya every one,
thought I'd share this.
If you are using Windows 10 and are like me, you may have ignored the 3D builder program that is included.
Now I have realised it's a handy little tool.
if you need to break up a .STL file then this will be a great help. (it does other things too)
I used it to break up a large part so it could fit into my build area. I just cut the pieces and then saved the left over piece. then adjusted the cut to leave another piece and saved etc...
worth a look