Step 7: Drill! (part III)
Here's the deal, drill down with the spade bit until the flat part starts to catch (please make sure the thing is centered first!) once this happens, stop, and pull the spade out. You'll have left a nice circular indention. (if you used the mortising attachment just drill down enough so that the washer can sit flush, or just above being flush.)
we need an indention so the washer will fit flush in there and not interfere with the two halves coming together in the "washer sandwich". so, move on and I'll show you what to do.