A couple others mentioned it would be a good idea to start a thread for cams. I think most of us already have learned the hard way that its really difficult to match up cams to a machine.
If you can, if you have cams and know which machine they go to, could you all post a picture (mugshot) of a cam from the side and from the top with a ruler for scale along with any info you have on which machine(s) it fits?
I'll go first with Singer tophat cams for 600 series Touch & Sews. they're the only type I currently own.
Sorry for the flash glare.
I measured it at 2 1/4" diameter. I believe they also work in 400 and 500 series machines and 700 series machines. 700 series machines also have a white version that doesn't work in the older machines. Please correct me if this is wrong.