Just for your information, if you copy the mill screenset to, say your desktop, then change the file extension from .set to .lset then it will turn it into a lathe compatible screenset.
You will also have to rename it or it will overwrite the standard lathe screenset when you paste it back to the Mach3 folder.
I have posted my screenset on the forum a couple of times but if I can't find the link I will put it on my cloud and give you a link to that.
Hood