Thread turning – Cutting data 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 to 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 pages 262 - 265. 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. In SMG classiﬁcation of workpiece materials involves a speciﬁc material standard in a speciﬁc condition assigned as reference for easy and unambigious adjustment of cutting data for any actual material compared to any Seco reference material. As examples the reference materials EN C45E for SMG P4 and EN 42 CrMo 4 for both SMG P5 and SMG H5 shown below in table 1 where the reference level material property is indicated. SMG Description P4 Low-alloy general structural steels, 0.25% < C < 0.67%wt Low-alloy Quench & Temper steels Properties Reference 520 < Rm < 1200 C 45E Rm = 660 N/mm2 SMG Description H5 Quenched & Tempered steels Properties 38 < HRC < 56 Reference 42 CrMo 4 50 HRC P5 Structural steels, 0.25% < C < 0.67%wt Quench & Temper steels 550 < Rm < 1200 42 CrMo 4 Rm = 700 N/mm2 Focusing speciﬁcally on EN 42 CrMo 4 in annealed condition, the ultimate tensile strength Rm may typically vary between Rm = 630 N/mm2 and Rm = 780 N/mm2, which provide a reference level for SMG P5. In Quenched & Tempered condition, the ultimate tensile strength Rm may typically be between Rm = 900 N/mm2 and Rm = 1100 N/mm2 thus still belongs to SMG P5. However, if hardened above Rm = 1200 N/mm2 it now belongs to SMG H5. SMG EN W.-Nr AFNOR BS UNI JIS AISI / ASTM GOST Condition P5 42 CrMo 4 1.1201 42 CD 4 42 CrMo 4 1.1201 42 CD 4 708 M 40 42 CrMo 4 SCM 440 (H) 4142, 4140 708 M 40 42 CrMo 4 SCM 440 (H) 4142, 4140 38HM 38HM Annealed Quenched & Tempered H5 42 CrMo 4 1.1201 42 CD 4 42 CrMo 4 1.1201 42 CD 4 708 M 40 42 CrMo 4 SCM 440 (H) 4142, 4140 708 M 40 42 CrMo 4 SCM 440 (H) 4142, 4140 38HM 38HM Quenched & Tempered Quenched & Tempered The EN 42CrMo4 quench & tempered steel could be used to illustrate the machinability dependence of materials’ condition. Rm_nom 700 1000 HRCnom 45 50 The graphs below indicate how speed recommendations for a nominal material conditions may be adjusted for relative Rm (left diagram valid for ISO-P) and for relative HRC (valid for ISO-H). To further illustrate how the SMG P5 nominal vc can be adjusted to a more accurate recommended vc we need ultimate tensile strength Rm data and in this case we use the EN 42 CrMo 4 quenched & tempered to Rm = 1000 N/mm2 according to above table (bold blue arrows). Assume that we ﬁnd that the SMG P5 nominal vc = 280 m/min for a certain product and machining. Then, actual recommended vc = 280 m/min x 0,75 = 210 m/min. Consequently in the SMG H5 the nominal vc can be adjusted using the hardened EN 42 CrMo 4 at HRC 45 (smaller grey arrows). Assume that the SMG H5 nominal vc = 50 m/min for a certain product and machining using a coated cemented carbide tool then, actual recommended vc = 50 m/min x 1,2 = 60 m/min. For further workpiece material details please see page(s) 266-273 and suggested cutting data at applicable pages. For more convenient cutting data handling we recommend applicable tools in My Pages – Suggest on www.secotools.com 16