There are many tools in our kitchens that work wonderfully with polymer clay, and it is very temping to "borrow" from your kitchen. It's fine to use a kitchen tool with clay, but once you've used it with clay, it should be dedicated for use with clay only. So if you use that meat mallet to texturize your clay, don't use it to pound the steak for supper. Pasta machines, food processors, knives, graters, peelers, and so on-- if you've used it with clay, it's gotta stay… out of the kitchen, that is.
Note: Tools made of metal or glass and with no nooks and crannies for clay to hide in can probably be cleaned well enough to go back to food use, but most clayers agree that it's best not to tempt fate. Besides, it's just a lot easier to have one tool you leave in the kitchen and another for your box of clay tools.