Introduction Holemaking SMG - Introduction 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. 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 646-657. SMG Description Low-alloy general structural steels, 0.25% < C < P4 0.67%wt Low-alloy Quench & Temper steels P5 Structural steels, 0.25% < C < 0.67%wt Quench & Temper steels Properties 520 < R m < 1200 550 < R m < 1200 Reference C 45E R m = 660 N/ mm 2 42 CrMo 4 R m = 700 N/ mm 2 SMG Description H5 Quenched & Tempered steels Properties Reference 38 < HRC < 56 42 CrMo 4 50 HRC Focusing specifically on EN 42 CrMo 4 in annealed condition, the ultimate tensile strength R m may typically vary between R m = 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 Rm 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 now belongs to SMG H5. SMG EN 42 CrMo 4 P4 42 CrMo 4 H5 42 CrMo 4 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 700 1000 HRC nom 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). Drilling Reaming Boring Annex 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 Rm data and in this case we use the EN 42 CrMo 4 quenched & tempered to R m = 1000 N/mm2 according to above table (bold blue arrows). Assume that we find that the SMG P5 nominal v c = 280 m/min for a certain product and machining. Then, actual recommended v c = 280 m/min x 0,75 = 210 m/min. 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 for a certain product and machining using a coated cemented carbide tool then, actual recommended v c = 50 m/min x 1,2 = 60 m/min. For further workpiece material details please see page(s) 646-657 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 13 secotools.com

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