I'm making a part that has an O-ring in a seat. I.e., not in a groove.
The part will be "loose" most of the time & I want the O-ring to
remain in its seat by having the seat diameter smaller than the O-ring's
nominal diameter. I.e., it'll be squeezed into the seat. How much
smaller can the seat be? The O-ring's nominal diameter is 0.7 & its
thickness is 0.1

Thanks,
Bob