SMG SMG SMG – Introduction The foundation for SMG is a classification of workpiece materials based on their type rather than their relative machinability and consequently it contains workpiece materials like composites. It is comprehensive enough, but still easy to identify which SMG a particular material belongs. Each SMG has a specific material standard in a specific condition assigned as reference to allow easy adjustment of cutting data for any actual material compared to any Seco reference material see page(s) 802-805. As example the reference materials EN C45E for SMG P4 and EN 42 CrMo 4 for both SMG P5 and SMG H5 see further details in the following tables. SMG Description Properties Reference SMG Description Properties Reference P4 Low-alloy general structural steels, 0.25% < C < 0.67%wt Low-alloy Quench & Temper steels 520 < R m < 1200 C 45E R m = 660 N/mm 2 H5 Quenched & Tempered steels 38 < HRC < 56 42 CrMo 4 50 HRC P5 Structural steels, 0.25% < C < 0.67%wt Quench & Temper steels 550 < R m < 1200 42 CrMo 4 R m = 700 N/mm 2 Focusing specifically on EN 42 CrMo 4 in annealed condition, the ultimate tensile strength R m may typically vary between Rm = 630 N/mm 2 and R m = 780 N/mm 2 , which provide a reference level for SMG P5. In Quenched & Tempered condition, the ultimate tensile strength R m may typically be between R m = 900 N/mm 2 and R m = 1100 N/mm 2 thus still belongs to SMG P5. However, if hardened above R m = 1200 N/mm 2 it instead belongs to SMG H5. SMG EN 42 CrMo 4 P5 42 CrMo 4 42 CrMo 4 H5 42 CrMo 4 W.-Nr 1.1201 1.1201 1.1201 1.1201 AFNOR 42 CD 4 42 CD 4 42 CD 4 42 CD 4 BS 708 M 40 708 M 40 708 M 40 708 M 40 UNI 42 CrMo 4 42 CrMo 4 42 CrMo 4 42 CrMo 4 JIS SCM 440 (H) SCM 440 (H) SCM 440 (H) SCM 440 (H) AISI / ASTM 4142, 4140 4142, 4140 4142, 4140 4142, 4140 GOST 38HM 38HM 38HM 38HM Condition Annealed Quenched & Tempered Quenched & Tempered Quenched & Tempered R m_nom HRC nom 700 1000 45 50 The EN 42CrMo4 quench & tempered steel could be used to illustrate the machinability dependence of materials’ condition. The graphs below indicate how speed recommendations for a nominal material conditions may be adjusted for relative R m (left diagram valid for ISO-P) and for relative HRC (valid for ISO-H). Speed recommendation based in material machining properties, steel Speed recommendation based in material machining properties, hardened steel To further illustrate how the SMG P5 nominal v c can be adjusted to a more accurate recommended v c we need ultimate tensile strength R m data and in this case we use the EN 42 CrMo 4 quenched & tempered to R m = 1000 N/mm 2 according to above table (bold blue arrows). Assume that we find that the SMG P5 nominal v c = 280 m/min / 918.64 sfm for a certain product and machining. Then, actual recommended v c = 280 m/min x 0,75 = 210 m/min / v c = 918.64 sfm x 0.75 = 688.98 sfm . Consequently in the SMG H5 the nominal v c can be adjusted using the hardened EN 42 CrMo 4 at HRC 45 (smaller grey arrows). Assume that the SMG H5 nominal v c = 50 m/min / 164.04 sfm for a certain product and machining using a coated cemented carbide tools then, actual recommended v c = 50 m/ min x 1,2 = 60 m/min / v c = 164.04 sfm x 1.2 = 196.85 sfm. For further workpiece material details please see page(s) 806 - 813 and suggested cutting data at applicable pages. For more convenient cutting data handling we recommend applicable tools in My Pages – on www.secotools.com These cutting data compensations for steels are fully implemented at www.secotools.com in MyPages (see QR-code in the upper right corner). 801 secotools.com