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The Lost Wax Casting Process
Wax: An Overview
Ceramic Slurry Dipping Schedule
The Sandcasting Process
The Chasing Process
Methods for Joining Bronze
Patinas
Investment Casting: 1930-1950
Project #2: Sandcasting a Bas Relief Bronze Plaque
How to Build a Bronze Casting Furnace
Foundry Safety
Furnace Lighting Procedure
Project #1: Direct Wax Sculpture, Ceramic Shell Casting

Methods for Joining Bronze

Riveting – Making a blind rivet

This can only be used when you have access to both sides of the sculpture.

1. Cutaway view of the two pieces to be joined.

2. Clamp the two pieces together and drill a hole through both pieces.

3. Using a larger drill bevel the edges of the hole on the top and bottom. Be sure that the bevel is deep enough.

4. Cut a rod of a matching metal that fits the width of the hole exactly – this will be the rivet. Cut it longer then the depth of the hole by twice the thickness of the rod. For example, if the total depth of the hole is 1”, and you used a 1/4” drill to make the hole, then you will need a rod 1/4” wide by 1-1/2” long. File the ends of the rod perfectly flat.

5. Take a scrap of steel rod and using the same drill bit from #2, drill a hole as deep as the width of the drill bit (for example, if you used a 1/4” bit, drill the hole 1/4” deep). This will act as an anvil and the hole will leave the correct amount of rivet above the surface.

a. Using a ball peen hammer, flatten one side of the rivet.

b. Work the end of the hammer around the edges of the rod so the end mushrooms and fills the bevels.

6. Turn the piece over, and using the ball peen hammer, flatten the other side of the rivet against a flat steel surface (like an anvil).

a. Turn the piece over several times and make sure the rivet ends are hammered tight.

b. The ends should be slightly rounded when you are finished, and no gaps should show around the edges.

7. Using a file or disc sander, flatten the ends of the rivets. They should disappear once sanded down.

Riviting
Bolting

Bolting

 

1. Cutaway view of the two pieces to be joined.

2. Clamp the two pieces together and drill a hole the proper size (see chart below) for the bolt you will be using.

a. To make sure you do not go through the top side, measure the total width and mark the drill bit with a piece of tape.

b. The threaded hole must be deep enough that the bolt will hold – about 1.5 times the width of the bolt is minimum, more is better.

3. Using the first hole as a guide drill out the hole in the bottom piece so the bolt can slide snugly into it.

4. Tap the hole on the top piece using the proper tap (see chart below).

Alternate methods of Bolting

5. Blind bolt: Bolt the two pieces together.

6. Blind bolt with countersunk head: This is a good method to attach a piece to a base. It is removable, clean looking, and strong providing there is sufficient depth to thread the bolt. Countersink the head of the bolt using a third drill. You will have to use a bolt with a hex or torque head. These are available as specialty bolts.

7-8. Hiding the end of the bolt: If there is not enough room for a blind bolt as shown, you can drill all the way through and, using a bronze bolt (available at marine hardware stores) hammer the end of the bolt like a rivet.

a. Once the bolt is in place, cut it off so that it protrudes above the surface about 1/2 its width (a 1/4” bolt should stick up about 1/8”).

b. Hammer the end of the bolt with a ball peen hammer to mushroom it so that there will be no gap between the bolt and the metal.

c. File or use a disc grinder to sand the surface flat. The bolt should disappear.

d. The edges of the hole do not need to be beveled in this case as the threads hold the pieces together.

(See the Tap and Drill Chart below)

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Table 1: Tap and drill

Welding

1. Side view of two pieces to be welded.

2. Bevel the edges of the area to be welded. This allows the weld to penetrate deeper making both a stronger bond and will help keep it strong when the welded bead is flattened.

3. Tack welds the ends of the sections.

a. Check the alignment of the seam. If it is good, continue. If not, you can bend it slightly to get it aligned or break the tack welds by bending and retack.

b. If the section to be welded is long, after you have tacked the ends, make a tack weld every 6” or so along the seam. This prevents the seam from becoming misaligned if it should heat up and try to warp.

4. Weld the seam and ends.

5. Using a sanding disc clean up the weld.

a. Do not sand below the surface, if there are imperfections (and there often are) just go back and build up the weld with another bead and grind it back down.

Welding
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Dan@RotblattSculpture.com
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