Answer:
My teeth are sharp, my back is straight, to cut things up it is my fate.
I am black when I am clean and white when I am dirty?
Iron on a mammal. Mammal on your feet.
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
What is never used unless it's in a tight place?
Iām grown from darkness but shine with a pale light. Very round I am and always a lady's delight.