Kings Crown Pattern

The kings crown pattern is something of a departure from my "normal" projects. A guy at work needed some 16 gauge brass cut into the crown shape for a medieval reenactment group he belongs to. We have a water-jet machine at work, but also a policy prohibiting doing personal projects on company machinery. So even though I have never cut metal on my CNC router at home, I told him I'd try to help him out. At the very least, I reasoned, I could cut a full-size MDF pattern of the crown.

Design

Although its function is similar to the paper crown you get at Burger King, the kings crown is not designed to wrap completely around your head. It is intended to be laced together at the back of the head with leather cord. This allows it to be slightly flexible and adjustable. Of course it would be a simple matter to add enough of the two inch wide band on each end to fit your head without the lacing.

Materials

As mentioned earlier, the crown was originally supposed to have been made of 16 gauge brass. 16 gauge is about 1/16", which is pretty stout. In the end, the crown was made from 16 gauge hot rolled steel (more about that later). Almost any material could be used, depending on your intended use. For a simple kid's craft, construction paper or poster board would be perfect. Light plastic sheeting would work as well.

Cutting

When I was originally approached about cutting the kings crown, the guy I work with had already created the crown pattern. Since we couldn't cut it on the company water-jet machine I figured it would be worth trying it on my ShopBot CNC router at home. His thought was to cut it from brass sheet which is pretty soft.

Unfortunately, he wasn't able to get the brass he wanted, so he settled on 16 gauge, hot rolled steel. I was pretty much prepared to just make him an MDF template to use as a pattern to cut it by hand. Curiosity got the better of me and I decided to experiment a bit cutting an old, steel pizza pan.

The results were quite surprising! I was able to cut the steel on my CNC router, which is equipped with a 3 hp Porter Cable router. For those who are interested, I used a 1/4", solid carbide, 2 flute, up-cutting, fish-tail router bit. Spindle speed was 13,000 rpm. Feedrate was 0.5 inches/second (30 inches/minute). Pass depth was 0.005 inches.

The router was programmed for a conventional (rather than climb) cut direction. However, after looking at both cut edges I would change that to a climb cut in the future. Both edges were very clean, but the climb cut edge was much smoother than the conventional cut edge.

Obviously, the crown pattern took quite awhile to cut with such a light pass and slow feedrate. Anyone with true metalworking machinery could likely make the cut more quickly. With some experimentation you could probably improve the speed and possibly take a deeper cut. My excitement simply comes from the fact that I was able to cut steel on my lightweight CNC router.