Coupling part, photosensitive drum, process cartridge and electrophotographic image forming apparatus

A process cartridge detachably mountable to a main assembly of an image forming apparatus, wherein the main assembly includes a motor, a driving rotatable member that receives a driving force from the motor, a twisted hole having a non-circular cross section and being substantially coaxial with the driving rotatable member, and a main assembly grounding contact provided in the hole, said process cartridge comprising:

• an electrophotographic photosensitive drum;
• process means actable on said electrophotographic photosensitive drum;
• a projection provided at a longitudinal end of said electrophotographic photosensitive drum, wherein when the driving rotatable member rotates with the hole and said projection engaged with each other in the state that said process cartridge is mounted to the main assembly of the apparatus, a rotational driving force is transmitted from the driving rotatable member to said photosensitive drum through engagement between the hole and said projection, with said projection being pulled into the hole, wherein said projection is provided with a plurality of engaging portions engageable with the hole;
• and
• a cartridge grounding contact, electrically connected with said electrophotographic photosensitive drum, electrically connectable with the main assembly grounding contact when said process cartridge is mounted to the main assembly of the apparatus, wherein said cartridge grounding contact is surrounded by said engaging portions as seen in a direction of a rotational axis of said electrophotographic photosensitive drum so as to be electrically connectable with the main assembly grounding contact.