Is there a kashrus issue in taking knives to be sharpened to a sharpener, knowing that the sharpener also sharpens non kosher knives?
In our experience, the knife sharpeners are constantly bathed in water so they do not get hot. Therefore, as long as the sharpener is clean, it is permitted to sharpen on a sharpener that is also used for non-kosher knives. (Butchers sometimes subscribe to a knife-sharpening service. The butcher must ensure he is getting back his own knives after sharpening.
