Hello, i've got a lathe insert toolholder question and hope someone can clear this up for me.Just decided to try inserts for the first time on my lathe,im usually running a mill and have been using brazed c5 and hss on the lathe.The toolholder i have is labeled SDJCR 4-2 and it apparently takes DCMT 2,1.5,1 etc. inserts.I have a handle on the insert size,radius etc. thanks to another thread here on the zone but i've not found anything on the web as yet to tell me what the 4-2 means, i've seen inserts for sale that also have this style of number and those dont have the 2,1.5, so im confused as to which inserts to buy.I had thought this might describe the screw size but im unsure,thanks for any help,Kevin