Doesn't the knurl score the cylinder walls? But I guess with such a shallow knurl to gain the .003 dia.
The top of the knurl will be flat and not pointed like on hand tools tools. I have not heard of that trick being used on pistons before.
I learn something every time you type Jerry.

Don

1967 GMC 9500 Fire Ladder Truck
"The Flag Pole"
In the Stovebolt Gallery
1946 2-Ton grain truck
1946 3/4-ton pickup,
1953 1-ton pickup
1957 1-ton flatbed dually,
1954 Pontiac Straight Eight
Of all the things I've lost in my life, I miss my mind the most!