He couldn't help thinking his mama had been a little tougher when she found out about the Immortals.
In metal bridges wrought iron has been replaced by mild steel - a stronger, tougher and better material.
She's tougher than Cynthia Byrne used to be.
Thus arsenic, antimony, bismuth, tin or zinc render the metal brittle, so that it fractures under a die or rolling mill; copper, on the other hand, increases its hardness, makes it tougher and more readily fusible.
The culinary arts showing proper deference a lot tougher pizza boxes on.