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T-82 10.1.3  Helical Gears The  chordal  thickness  of  helical  gears  should  be  measured  on  the  normal  surface basis as shown in Table 10-3.  Table 10-4 presents the equations for chordal thickness of helical gears in the radial system. Table 10-3     Equations for Chordal Thickness of Helical Gears in the Normal System Table 10-4     Equations for Chordal Thickness of Helical Gears in the Radial System NOTE:  Table 10-4 equations are also for the tooth profile of a Sunderland gear. 10.1.4  Bevel Gears Table 10-5 shows the equations of chordal thickness for a Gleason straight bevel gear. Table 10-5     Equations for Chordal Thickness of Gleason Straight Bevel Gears m  =  4 a   =  20° S   = 90° z1 =16 z2  =  40 z1 –– =  0.4 K   =  0.0259 z2 ha1=  5.5456 ha2=  2.4544 d 1  =  21.8014° d 2  =  68.1986° s1  =  7.5119 s2  =  5.0545 sj1 =  7.4946 sj2 =  5.0536 hj1 =  5.7502 hj2 =  2.4692 Obtain from Figure 10-2 (on the following page) pm – s2 pm ––– – (ha1 – ha2)tana – Km   2         s 3 s – –––––       6d 2        s 2 cosd ha + ––––––––              4d No. Item Example 1 2 3 4 5 Formula Symbol sn zv qv sj hj Normal Circular Tooth Thickness Number of Teeth of an Equivalent Spur Gear Half of Tooth Angle at Pitch Circle Chordal Thickness Chordal Addendum    p (––  + 2xn tanan )mn    2     z –––––– cos3b 90     360xn tanan ––  + ––––––––––– zv             pzv zv mn sinqv zv mn –––– (1– cosqv ) + ha    2 No. Item Example 1 2 3 4 5 Formula Symbol sn zv qv sj hj Normal Circular Tooth Thickness Number of Teeth in an Equivalent Spur Gear Half of Tooth Angle at Pitch Circle Chordal Thickness Chordal Addendum m  =  4 at  =  20° b   =  22° 30' 00" z    =  20 xt   =  +0.3 ha  =  4.7184 sn  =  6.6119 zv  =  25.3620 qv  =  4.04196° sj   =  6.6065 hj   =  4.8350 p (––  + 2xt tanat )mt cosb    2     z –––––– cos3b 90       360xt tanat ––  + ––––––––––– zv             pzv zv mt cosb sinqv zv mt cosb ––––––––– (1– cosqv) + ha        2 mn =  5 an  =  20° b   =  25° 00' 00" z    =  16 xn  =  +0.2 ha  =  6.0000 sn  =  8.5819 zv  =  21.4928 qv  =  4.57556° sj   =  8.5728 hj   =  6.1712 No. Item Example 1 2 4 5 Circular Tooth Thickness Factor (Coefficient of Horizontal Profile Shift) Circular Tooth Thickness Chordal Thickness Chordal Addendum Symbol K s1 s2 sj hj Formula