An often asked question is how thick can the yarn be that will work on a CSM?
One way to answer that is to first consider how wide the needle cylinder slot actually are on the cylinder you intend to be using on your machine.
Know that a cylinder that has a high cylinder slot count (ie. 72) will have much more needles to accommodate on the same circle as a cylinder with perhaps almost half as many (i.e. 40 needle slots). See these two cylinder images as example.
Technically the lower slot count cylinder might have slightly wider slots however there is still a maximum width to that slot in order to correctly direct the cylinder needle and keep it within its channel.
The NEXT POINT is the properties to the fiber you’ve chosen to use on your machine.
I myself use fingering and light fingering sock weight yarn on my machine without issues, however I have met persons who use home spun wool on their machines, sometimes using the 60 needle slot cylinders as an example.
Personally if I have heavier yarn I would use a lower slot count, use mock rib perhaps and consider whether the fiber will pass doubled into the slot with the cylinder needle during use.
MORE INFO TO BE ADDED TO THIS POST.