This paper investigates the influence of design parameters on cogging torque in permanent magnet machines. The study shows that the combination of slot and pole numbers significantly affects cogging torque, influencing the optimal skew angle, magnet arc, and number of auxiliary teeth/slots. A factor, proportional to the slot and pole numbers and inversely proportional to their least common multiple, is introduced to indicate the "goodness" of the slot and pole number combination. A higher "goodness" factor results in larger cogging torque. Cogging torque arises from the interaction of permanent magnet mmf harmonics and airgap permeance harmonics due to slotting. It causes pulsating torque and can lead to speed ripples and vibrations, especially at low speeds. The paper analyzes the effects of various design parameters, including slot opening width, airgap length, magnet thickness, magnet pole-arc to pole-pitch ratio, magnetization distribution, and skewing, on cogging torque. The optimal magnet pole-arc to pole-pitch ratio is determined based on the slot and pole number combination. The paper also discusses the use of auxiliary teeth and slots to reduce cogging torque. Skewing the magnets or teeth can reduce cogging torque, with the optimal skew depending on the slot and pole number combination. The stator slot opening also affects cogging torque, with wider openings increasing the torque. The study concludes that certain design parameters, particularly the slot and pole number combination, have a significant effect on cogging torque. A simple factor, $ C_T = 2pQ_s/N_c $, is introduced to indicate the "goodness" of a slot and pole number combination from the viewpoint of cogging torque. An odd number of slots is preferred for minimizing cogging torque in 2-pole motors. The paper also highlights the importance of considering other performance factors when selecting design parameters.This paper investigates the influence of design parameters on cogging torque in permanent magnet machines. The study shows that the combination of slot and pole numbers significantly affects cogging torque, influencing the optimal skew angle, magnet arc, and number of auxiliary teeth/slots. A factor, proportional to the slot and pole numbers and inversely proportional to their least common multiple, is introduced to indicate the "goodness" of the slot and pole number combination. A higher "goodness" factor results in larger cogging torque. Cogging torque arises from the interaction of permanent magnet mmf harmonics and airgap permeance harmonics due to slotting. It causes pulsating torque and can lead to speed ripples and vibrations, especially at low speeds. The paper analyzes the effects of various design parameters, including slot opening width, airgap length, magnet thickness, magnet pole-arc to pole-pitch ratio, magnetization distribution, and skewing, on cogging torque. The optimal magnet pole-arc to pole-pitch ratio is determined based on the slot and pole number combination. The paper also discusses the use of auxiliary teeth and slots to reduce cogging torque. Skewing the magnets or teeth can reduce cogging torque, with the optimal skew depending on the slot and pole number combination. The stator slot opening also affects cogging torque, with wider openings increasing the torque. The study concludes that certain design parameters, particularly the slot and pole number combination, have a significant effect on cogging torque. A simple factor, $ C_T = 2pQ_s/N_c $, is introduced to indicate the "goodness" of a slot and pole number combination from the viewpoint of cogging torque. An odd number of slots is preferred for minimizing cogging torque in 2-pole motors. The paper also highlights the importance of considering other performance factors when selecting design parameters.