I made an oak bed with turned bedposts, "Pilgrim" style a few years back. It was my own design, based loosely upon one of the very few photos I could find of a bed from this period. I borrowed the design from the top of the Brewster and Carver chairs for the tops of the posts. The headboard posts are about 42" high, with a turned cylindrical section above the rail, terminating in the egg looking design found on those old chairs. The headboard is a flat paneled section with chamfered rails and stiles and a carved top rail, floating in mortises in the sides of the turned posts. I do not remember whether I made the mortises prior to or after turning. Generally, I try to do most of my mortising prior to turning, though in some case you can leave square sections of waste beyond the turned design (in my case, above the top of the post, and the bottom of the post I left square). It will be easier to mortise if you do it in the square. It will be easier to turn a smooth shape if you do the mortise after. My mortise was the entire height of the headboard panel, maybe 24' - 30", as I made a side stile to make the headboard assembly more secure. You could build a router platform on the bed of your lathe and use a plunge router to create the mostise after turning. I have an old Bridgeport that I sometimes use for things like this, as I can clamp the work piece to the table and move the table about below the router bit. Short of these, my guess is that if you are careful in the turning, you would be okay cutting the mortise first. I like the idea of the waste tenon as well.
Rob
