The designation follows ISO 5608 and is the same for every maker. After the insert size a maker may add letters of its own, for instance for internal coolant or special shanks: read those in its catalogue.
Inserts it takes
It takes CNMA / CNMG inserts, size 12: the pages below explain each one. Grade and chipbreaker are chosen from the catalogue, by material.
The left-hand version is PCBNL 2525M12: same insert and size, mirrored. Right or left depends on the feed direction and on how the tool sits on the turret.
What it is for
Style B has a 75° cutting edge angle (side cutting): it is used for 75° roughing.
Designation to ISO 5608 (toolholders) and ISO 6261 (boring bars); cutting edge angles as in the ISO 5610 standards. No maker has approved this page: the catalogue is what counts.
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