In this research the effect of bevel angle, oblique angle, shear velocity and blade type (smooth or serrated) were studied on shear strength as well as shear energy per unit area of pyrethrum flower stalk, using double shear tests. Also, the effects of velocity on force and energy for picking flowers were studied. Experiments were carried out by using an Instron testing machine. Studying the influence of bevel and oblique angle, showed that these two factors had a significant effect on shear strength as well as shear energy per unit stalk area, but their interactions werenot significant. The mean values of the shear strength and energy per unit area were 2.29 MPa and 2.96 mJ/mm2, respectively. It was shown that, with an increase in the shear velocity (from 20 to 500 mm/mm), the shear strength and energy per unit area were decreased. These decreases were not significant for shear strength and energy per unit area from 200 to 500 mm/mm and 20 to 200 mm/mm, respectively. Both shear strength and shear energy per unit area were higher for serrated blades than those for smooth blades. Of course, there were no significant differences in shear strengths but the sheare energy per unit area was different at significance level of 1%. The mean values of shear strenth for smooth and serrated blades were 2.5 N and 2.9 N, respectively and for energy per unit area 1.71 and 4.80 mJ/mm2, respectively. So, the smooth blades are recommended to cut this crop. The result of the determining of picking force of flowers shown that with an increase in picking velocity, the picking force and energy increased, but tensile strength and energy per unit area decreased. The mean values of tensile strength and energy per unit area were recorded as 1.56 MPa and 3.7 mJ/nim2, respectively.
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