Section 17 Strength and Durability of Gears - SDP/SI

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ELEMENTS OF METRIC GEAR TECHNOLOGY Nitriding Steel Module 1.5 A 0.2 Depth, mm B 0.3 2 0.2 0.3 PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM Table 17-14A 3 0.3 0.5 4 0.4 0.7 5 0.5 0.8 6 0.6 0.9 8 0.7 1.1 10 0.9 1.4 15 1.2 2.0 NOTE: For two gears with large numbers of teeth in mesh, the maximum shear stress point occurs in the inner part of the tooth beyond the carburized depth. In such a case, a larger safety factor, S H , should be used. Table 17-15 Gears with Nitriding – Allowable Hertz Stress Surface Hardness Material σ H lim kgf/mm 2 (Reference) NOTE: In order to ensure the proper strength, this table applies only to those gears which have adequate depth of nitriding. Gears with insufficient nitriding or where the maximum shear stress point occurs much deeper than the nitriding depth should have a larger safety factor, S H . Material Structural Steel or Alloy Steel SACM 645 etc. Over HV 650 Standard Processing Time Extra Long Processing Time Table 17-16 Gears with Soft Nitriding (1) – Allowable Hertz Stress Nitriding Time Hours 2 4 6 less than 10 NOTES: (1) Applicable to salt bath soft nitriding and gas soft nitriding gears. (2) Relative radius of curvature is obtained from Figure 17-6. 100 110 120 σ H lim kgf/mm 2 20 1.5 2.5 25 1.8 3.4 Relative Radius of Curvature mm (2) 10 to 20 90 100 110 Metric 0 10 120 130 … 140 more than 20 80 90 100 I R T 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 T-169 A
I ELEMENTS OF METRIC GEAR TECHNOLOGY R T 1 Relative Radius of Curvature (mm) 0 60 50 40 30 PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM Gear Ratio 1 2 3 4 5 6 Metric 0 10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A 20 10 α n = 25° 22.5° 20° No. Item Symbol Unit Pinion Gear 1 Normal Module m n mm 2 2 Normal Pressure Angle α n 20° degree 3 Helix Angle β 0° 4 Number of Teeth z 20 40 5 Center Distance a x mm 60 6 7 8 9 10 Coefficient of Profile Shift Pitch Circle Diameter Working Pitch Circle Diameter Tooth Width Precision Grade x d d w b mm +0.15 40.000 40.000 20 JIS 5 – 0.15 80.000 80.000 20 JIS 5 11 12 Manufacturing Method Surface Roughness Hobbing 12.5 µm 13 Revolutions per Minute n rpm 1500 750 14 15 16 17 18 19 20 21 Linear Speed Direction of Load Duty Cycle Material Heat Treatment Surface Hardness Core Hardness Effective Carburized Depth v m/s cycle mm 3.142 Unidirectional Over 107 Cycles SCM 415 Carburizing HV 600 … 640 HB 260 … 280 0.3 … 0.5 T-170 20 10 20 15 10 8 7 6 5 80 100 150 200 300 400 500 600 700 800 Center Distance a (mm) Fig. 17-6 Relative Radius of Curvature 17.2.17 Example Of Surface Strength Calculation Table 17-16A Spur Gear Design Details
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Section 17 Strength and Durability of Gears - SDP/SI

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