With a Dexter Boning knife mounted in the vice with the depth key in the top position, the stones hit the vice and scratch the vice.

I'm using the 18 degree recommendation in the manual. How do I keep from ruining the vice with the stones. See attached.

Welcome to the forum!!!

Although the depth key is a good guide, try reclamping the knife as high in the clamp as you can (while still getting a good grip)... see if that gives enough clearance. Just make a note of how you clamp it so you can repeat it next time.

You can also just sharpen a degree or two higher... you probably won't notice a difference in use.

A layer of masking tape on the top of your jaws gives very nice feedback too. As soon as you hit tape...it feels very different.