Ho to create a circle section on a hollow cylinder? 1

[mdama]

Hello
I was wondering how I can create a circular section (partition)on a non flat surface like a hollow cylinder?
Thanks

 

[FEA way]

If you select Partition Face: Sketch and pick the cylindrical surface, you will be asked for sketch plane (use datum plane tangent to cylindrical surface). After that you have to specify the projection distance and direction. Sketch a circle and it will be automatically projected creating partition.