I had made a 5' lighted star for my brother from 2" Fir a couple of years ago using LED Christmas lights, and he asked me to make a matching cross. I used the same basic technique of routing a wire path into the back of the pieces and drilling holes for the individual LEDs. I had then covered the back with a 1/4" on the star but decided to hide the seams on the side of the cross by also routing an inlay to cover the wire path. Also, instead of having the light socket sit loosely in a hole drilled through the front, I drilled a clearance hole for each LED and a countersink hole for the socket. This allowed the wire path cover to hold the LED firmly in place and upright. The downside is changing a bulb meant you have to remove the wirepath cover, so it has to be maintenance friendly. I searched the web for a standard ratio for a Christian cross, but didn't find a consensus. My design ended up 5' x 4' with the vertical center 18" from the top.
Step 1: Initial Cutout
I chose a 6' 2 x 12 piece of straight grained Fir that I had left over from the lighted star I had made earlier. Both the 5' upright and 4' cross arm were cut from the one piece. The design calls for 2" at each end with the junction square at 4". I laid out a 4" square on both pieces at the center junction and drew saw lines from the outside corners of the square to the respective ends 1" from the center line. A hint here, cut the 4" square sides from the full length of each piece first otherwise you won't have anything to guide to after the angles are cut.
Step 2: Inlay Routing
My design(in my head) was to was to rout a 1/4' deep 1" wide inlay and then rout a deeper wire path. I have very little experience with routing as can be seen, and ended up trying both a handheld router with a guide and the same router bit in my table shaper. I did better with the shaper. If I try something similar in the future I will build a guide that only allows the router to cut in a straight line. Everyone has a wish list, maybe mine should include a ShopBot.
Step 3: Making a Guide for LED Holes
I wanted to make sure that I could precisely(relatively speaking) have my LEDs on a straight line as I will chamfer the top finished edge to where the LEDs come through the holes. This will allow the LED to be seen better from the side. I made a jig for my drill press and set the depth. I marked the spacing for each hole and I could align front to back easily. By the way 2" centers starting 1" from the end comes out to exactly 100 lights.
Step 4: 1/2" Countersink Holes for LED Socket
Here is where the drill jig helped with accuracy. The holes for the LED socket needed to be centered on the already drilled 1/4" clearance holes AND stopped 1/8" short of going through. I adjusted the drill press stop and used a Forstner bit.
Step 5: Wire Path Routing
It was at this point that I had to make a decision as to how I was going to get the wires around the corners of the square. I knew I was going to join the cross junction by cutting out half of the square on each piece so I did that at this time with a dado blade in the table saw(sorry no pictures). Remember back at the start when I suggested cutting the 4" sides of the square by cutting it the full 5' length? I didn't, and struggled to make sure I had the cut right or the cross arm would not be horizontal. I ended up extending the inlay rout on the cross arm and routed the wire path through the junction. The wire path rout is a 1/4" by 1/2" deep from the bottom of the cover inlay, or 3/4" from the back surface. I had originally planned on 1/2" by 3/4" wire path, but as you will see later, I was able to eliminate half of the wires.
Step 6: Initial Assembly & Chamfer
I needed to assemble the two pieces at this time to put a 45 degree chamfer on the front edges. I was aiming for the chamfer to cut about 1/3 of the way through the LED clearance hole, and thus the concern early on about hole alignment and the drill guide. The purpose was to enhance the side aspect of the LED since it sits 1/8" below the surface.
The pieces were now ready for staining. I used a single coat of mission oak, and several thin coats of clear urethane.
Step 7: Wiring Mod
Looking at the LED string out of the box, it was obvious that two of the wires ran completely through the string, only connecting the tail end socket. The usable circuit consists of two LEDs connected in parallel, with 50 pairs in series. I also noticed that there is a voltage drop in the plug, but none in the socket. Since I was going to eliminate the socket and connect the string end back to the plug anyway, I also eliminated the two unneeded wires.
Step 8: Final Assembly
This is where I wished I had stuck with the original 1/2" by 3/4" wire path rout. The wiring fit, but very snugly.
I didn't realize that I had not taken any pictures of the inlay boards, or the back of the cross with them on it. Each one ended up a custom size as my routing skills leave a lot to be desired.
I had cut 1/4" solid fir pieces to fit each inlay, and as I got the wires to lay in the path I secured each inlay with #4 3/4 brass screws. After final assembly I gave the back another coat of clear urethane to help seal the inlays.