Hi Janey,
Thanks for the post. I have a fancination with pinkers and cutters. I have them in all shapes and sizes, by many different companies and different, what I call heftiness!. I have one that can pink through leather ( not that it needs pinking) like butter.
My straight cutters are for wool for rughooking. All cut from pressure, not sharpness of a blade.
From my experience, the lengthwise grain is what most people are concerned with and it frays less when pinked. Think of a pair of pants. The leg seams are parallel to the length of grain. The waist and hem raw edges are probably turned under or bound. Same with arms and bodice are cut on the length of grain, so the same concept.
Not to turn off topic, but Merry Christmas!
Maria