# Thread: Insert toolholder (4-2)? question

1. ## Insert toolholder (4-2)? question

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

2. http://www.usshoptools.com/current_y...GS_344_376.pdf

http://www.usshoptools.com/current_y...GS_355_376.pdf

That toolholder takes a DCMT 21.51 or DCMT 21.52

The D stand for 55 dreg. diamond
C =7 dreg. side clearance
m= is the tolerance of the insert
T= hole with countersink
2 stands for the size of the insert , They measure the size of an insert by how big of a circle will fit inside the insert this is known as the IC or inside circle. The circles step up by 1/8 inchs on inserts so 2 x 1/8 = 1/4 inch circle , So whatever that first number is mutiply it by 1/8 inch and thats you IC.
1.5 is the thickness of the insert , mutiply it buy 1/16 inch so 1.5 x 1/16= 3/32 inch thick insert
1 stands for the nose radius mutiplt it by 1/64 so 1= 1/64 2= 1/32 3=3/64 4 =1/16

Hope this helps

3. thank you Tim for the reply and the links, cant wait to put this tool to work and reduce my time on the grinder,Kevin

4. Hi !
I've just visited this forum. Happy to get acquainted with you. Thanks.