Introduction: Jerusalem Cross of Welded Concrete Nails
This is a Jerusalem cross. It is really four small crosses and one larger cross for a total of five. I did a similar Instructable quite a few months in the past, but its construction was quite different.
The earlier version involved cutting the nails and brazing the pieces back in place. I wanted to try an all-welded construction. The welds are all done from behind the finished surfaces, except for the weld in the center that is covered with brazing rod for decorative effect.
Click on this link to see the earlier version and to read about the significance of the Jerusalem cross.
Step 1: What You Will Need
In the USA both Home Depot and Lowe's home improvement stores now sell 2 1/2 inch (6.35 cm) square cut concrete nails in boxes of 60.
I am using a flux-core wire feed welder, some holding jigs I made, some brazing rod with a MAPP gas torch, a wire wheel, and some spray shellac. I will also add a loop made from a small nut welded behind the nails and some bent wire for hanging on the wall.
Step 2: Small Cross Array
This photo shows the array of the four small crosses welded together from four nails. Holding the nails in place for the desired end product is very difficult by hand. The ends of the nails want to slide away in the direction shown by the red arrows. A homemade jig makes holding the nails in place easy. See the next step.
Step 3: The First Jig
Cut a wooden square. The dimensions equal the length of the nails. This is approximately 2 1/2 inches, but may vary a little. From experience, it would be better if the block were oversize by 1/32 to 1/16 of an inch on each side.
I used 1/2 inch angle iron to make my jig. The piece shown (red paint on the end) is a piece of scrap for purposes of this photo. It is a little short. Weld the jig where you see the red paint. Check to be certain heat from the weld has not pulled the corner so it is no longer square.
Weld all four pieces of angle iron so they fit closely around the wooden block. My finished jig is at the right of the photo.
I debated with myself about the bother of making jigs. But, as friends saw the finished Jerusalem cross I began to get requests for more and more copies. A good set of jigs makes it easy to produce consistent duplicates.
Step 4: Refinements to the Jig
I wanted to be able to place nails into the jig with consistent precise positioning. This meant adding small tabs of steel welded in place. The ends of the nails rest against these.
Those outlined in green are 1/8 inch steel 1/2 inch wide. They hold the heads of the nails 1/2 inch out from the inside corners of the jig.
Those outlined in yellow are scraps of nails from another project. Placing them was a matter of resting the nail heads against the tabs outlined in green and aligning the nails so they appeared parallel to the nearest side of the jig. Whenever possible I locked a scrap of nail in place with a locking pliers, like a Vise-Grip. Then I tack welded that scrap of nail in place.
See the second photo. It shows the jig from the underside. (The yellow boxes are not message boxes. That feature was not saving when I tried to upload my text.) I welded four thin metal tabs near the corners to support the heads of the nails. See the yellow boxes. Originally I placed the jig on the bottom of an aluminum fry pan for welding. A lot of hot spatter bounced off of the fry pan and stuck on the good side of the nails. This resulted in a lot of difficult extra cleanup work. These metal tabs allow me to hang the jig in my vise so the spatter falls harmlessly to the floor. The rods in red boxes are for clamping the jig in my vise.
Step 5: Prepare the Nails
The nails usually have a side with a more pleasing appearance and a side that appears a bit rough. Turn four nails with the more pleasing side up. Ignore the aerosol can in the photo. Originally I sprayed the nails with cooking spray to keep spatter from sticking, but I was able to eliminate that with a modification to the jig described in the previous step.
Step 6: Laying Up the Nails and Welding
One by one turn the more pleasing side of the nails down and insert them into the jig. You can see how the extra tabs welded into the jig hold the heads and tips of the nails in their proper positions.
The last nail's head must be slipped under the first nail's pointed end. Check to be certain the heads and the tips of all nails rest securely against the tabs that mark their places.
Weld the nails together where they intersect. When weld material cools, it contracts. That can cause each joint to pull the nails upward a little until quite a large gap can appear at the last joint to be welded. My suggestion is to weld two joints opposite each other. Wait a little for the welds to cool. Press all four nails down. Weld the two remaining joints.
When finished welding, tap the nail assembly out of the jig with a hammer.
Step 7: The 2nd Jig
Another jig helps produce the large center cross with more consistent results. This jig supports four nails clamped in place for welding them together at their tips.
It is made of 1/8 x 1/2 inch strap iron. One piece 4 1/2 inches long is the main part. Two wings 2 1/8 inch long each are welded to it at 90 degrees to make an "X." (One of my wings is not quite 90 degrees to the main piece. So, I had to add scoring marks on all four arms to define the exact position for the nails before welding. Some of the scoring marks are visible.)
I also added a round rod post to the underside of the jig so I can clamp it in the vise easily.
I bent the arms upward just a little so the finished welded cross would be flat. There is a square of aluminum at the center to prevent accidentally welding the tips of the nails to the jig. The aluminum is from an old automobile license plate.
Step 8: Clamping the Nails to the 2nd Jig
Nails on this jig are fitted with their better side facing upward. I line a nail up with the jig so its center is above the scoring lines and attach a clamp. Then I do the same with the nail opposite so the nail tips meet. Finally I add the two nails at 90 degrees to the first two.
I have found I get better results if I attach the welder's grounding clamp directly to one of the nails rather than to the support post by which the jig is held in the vise.
I try to hold the welding gun so the wire is straight down on the joint. Check to be certain the tips of all four nails are covered by the weld. Weld again while the joint is hot if one nail tip is not really part of the weld. Turn the assembly over and weld the nail tips from the backside, too.
Step 9: Finished Large Cross
Here you see the finished large cross on the jig, but with the clamps removed. Check again to be sure the four nails are 90 degrees apart from one another and that the whole assembly is flat, not bowed up or down at the center. The heat from the welding has softened the nails enough that you can make corrections, especially while the weld joint is still hot. The results will be quite consistent, but will still vary a little because the nails are sometimes wider or narrower and because they are still placed by hand, even though there is a good jig to serve as a guide. Some boxes of nails are magnetized. (Notice the filings on the nail head in the 10 o'clock position.)
Step 10: Weld the Two Assemblies Together
Welding the two assemblies together can be more difficult than a person would think. The problem is getting a good alignment of the two pieces.
I place one end of the large cross into the vise. The good side is up. I hold the welded assembly for the small crosses under the large cross. The good side is also up. I try to align both so the square openings are as even as possible. The sides of the nails are all on diagonals. This can trick your eye into thinking something is straight when it is not. Try to visualize a line running through the center of the nails.
Attach one spring clamp as shown. Watch that pressure from the clamp does not cause the nail assemblies to slip and move. Hold the unclamped portion of the lower assembly in position so it does not shift in position.
Step 11: Add a 2nd Clamp and Turn to Weld
While still in the vise, add a second spring clamp to hold the two assemblies together. Remove from the vise and carefully turn over so the good side is down. Clamp into the vise as before. Make one weld to fasten the two assemblies together. Remove the clamps. Remove the cross from the vise and look at it carefully. If anything is not aligned as you want it, you may be able to bend a little while the weld is hot. If the alignment is not good at all, cut the weld apart with a cutting wheel on a Dremel and try again.
Step 12: Weld
When everything is as you want it, make a second weld opposite the first to hold the two cross assemblies together. (The clamps would not necessarily need to be attached after the first weld in the previous step.)
Step 13: Wall Hanger
I experimented with various hangers on the back of the cross for hanging it to a wall. I settled on welding a small hex nut to the back. The photo shows a nut held in place with a small Vise-Grip pliers. Before clamping the nut for welding, examine the cross from the front to decide if it looks better in one position rather than in another. Then choose which arm will receive the nut for the hanger. The cross assembly is in my vise. A small tack weld is all that is necessary, but hold the arc for a couple of seconds so the weld penetrates. Use lower heat than used welding the nails. The nut melts away very easily. Start the weld on the nail and move the arc toward the nut. Remove the pliers and weld the other side of the nut, too.
Step 14: Wire Loop
Add a wire loop to the hole in the nut so the cross can hang on a nail in the wall, but still not show when the cross is viewed from the front. Cut a piece of wire 1 5/8 inches long. Grind the ends square. Bend it in an oblong loop. Bring the ends together.
I use an aluminum backing plate when welding thin wire to reduce the risk of blowing it away in molten drops. It is a piece of channel from an old storm door. Here you see it in a vise. I need to clean it often with a file so there is good electrical contact to ground for welding. A spring clamp holds one end of the wire loop. Use a short burst at low power. Wait until the weld cools. Give it another short burst if you need to build up the weld.
Step 15: Clean With a Wire Wheel
Clean the cross assembly with a wire wheel to remove dirt and slag. You may need to get into the corners with a small wire wheel on a Dremel tool. Examine carefully for any spatter beads. Most can be knocked off easily. Occasionally you may need to use a file to remove one.
Step 16: Add Braze
Adding braze to the center of the large cross is decorative. I use a MAPP gas torch. It is a little slow to reach brazing temperature, but is also not so very hot that the nails are in danger of melting away. I find I get better results from my MAPP gas torch if I place the nail cross on a piece of brick before brazing. The brick heats up and reflects heat back to the nails. The heat from the torch also causes iridescent color patterns to form on the surface of the nails. These add quite a lot to the appearance.
Use a wire brush cup in a Dremel to remove slag from the braze. Hold the cross and the Dremel both firmly so the Dremel does not skate and remove some of the iridescent bluish surface colors. If a very small area of the coloration is blemished, you can hide it with a light application of color from a dark blue or black permanent marking pen.
Any milky white coating that remains on the nails from the brazing flux can be removed with a cloth buffer wheel in a Dremel tool. Be careful not to buff so hard that the bluish colors from the heating are also removed.
Step 17: Shellac
Place the cross on a piece of newspaper with the backside up. Apply a light coat of spray shellac to protect against rust. When dry turn the cross or crosses over and apply a light coat or two to the front side. Use a circular motion and spray from different directions to apply shellac to the sides of the nails, too.
Hang on your wall, or wrap and give as a gift. Be careful not to scratch or scrape the bluish colors in the finish. They can and do come off.
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