LNMU0303 is a small, double-sided milling insert with four cutting edges, made for high feed milling. SDMT1205 (full code SDMT120512) is a square milling insert. A cutter body or shank cutter is named after the insert it takes, so the insert code tells you which cutter to look for.
What LNMU0303 means
An insert maker's catalogue lists the LN*U03 inserts as double-sided inserts with four cutting edges, for cutters of 16 to 50 mm diameter, with a maximum depth of cut of about 1 mm. Letters after the size, such as ZER or UER, are added by the insert maker, so LNMU0303ZER and LNMU0303UER are two versions of the same size.
L: the insert is a rectangle (ISO 1832 shape code).
N: a 0 degree clearance angle, which allows a double-sided insert.
M: a tolerance class.
U: with a hole, two countersinks and chip grooves on two faces.
0303: the size code. Check the dimensions in your insert maker's catalogue.
What SDMT1205 and SDMT120512 mean
S: square, 90 degree corner.
D: 15 degree clearance angle.
M: tolerance class M.
T: with a hole, one countersink and a chip groove on one face.
12, 05, 12: the three number pairs give the size, the thickness and the corner radius, in that order. SDMT1205 is the insert size; the last 12 in SDMT120512 is the corner radius code, 1.2 mm.
What high feed milling means
High feed milling takes a shallow cut at a high feed per tooth. The small engagement angle directs most of the cutting force back along the cutter axis. That is why the maximum depth of cut above is only about 1 mm.
