Art. II. Making a Copper Trade Kettle, by J. Gottfred. Photos by A. Gottfred.

Seam Punch— The completed seam tool (punch).

The next step is to prepare the mandrel that you are going to use to form the kettle body.

For the kettle's main mandrel, I used a 3 ¾" (outside diameter) seamless pipe with a ¼" wall. All of the measurements in this article assume that you are using the same. This pipe is readily available at metal suppliers. I suggest that you avoid using scrap because you need a piece that is cut square and has smooth sides.

Clamp the pipe in your vise and touch up the face to remove any deep saw marks. Be careful not to get carried away and file the face out of square or your kettles will be lopsided!

Slightly round off the outside edge of the pipe. This will help the kettle go on and off the mandrel, and prevent the edge from cutting the copper.

Now you will need to determine the correct material length to use with the mandrel and the 1/8" seaming tool. You may need to cut several test strips of the copper material that you will use for the kettle, check the fit on the mandrel, and test the seaming tool.

Measure the outside diameter of the mandrel.

Multiply the diameter by 3.14.

Add three times the width of the groove in the seaming tool. For the 1/8" tool, add 3/8".

Add another 1/8" for ease.

Final width of material for the 3 3/4" diameter mandrel is 12 7/16".

Cut a strip of copper 12 7/16" long by 1" wide.

Mark 1/8" from each end of the strip.

Using the straight-edged mandrel, hammer with the raw hide hammer to fold one 1/8" end down 90°.

Flip the piece over, and using a thin ruler, continue to work the 90° fold over into a U-shaped channel.

Fold the other end to form a U-shaped channel, but make sure that it bends in the opposite direction. One will go up, the other will go down.

Bend the test strip on the mandrel. Bend it smoothly by pushing your fingers along the copper– this will keep the copper from kinking.

Hook the two U-shaped channels together.

Place the linked copper strip on the smaller round mandrel, and use the seaming tool to punch the seam closed. The result should be a tightly-locked circle.

Test the fit of the circle on the large mandrel. It should fit over the mandrel as tightly as possible, yet be loose enough that the copper will slip easily over the pipe. Continue with these tests until you find just the right width of material required for your seaming tool and this mandrel.

For future reference, mark the mandrel with the material width required and the seam width used.

   Kettle Body Template— The kettle body should be cut out as shown above. Fold lines are shown as dashed lines. 'Over' means fold up from the page, 'under' means fold down from the page.

You have determined the width of material that is required for the kettle body. You must now decide how tall the body should be. I chose a finished height of 5".

Once you've chosen a finished height for the kettle, add 1/2". For this example, the dimension of the required piece is 5 1/2" tall by 12 7/16" wide. Cut out the piece from the .022 copper sheet.

Mark 1 1/4" in from the top edge.

Mark 1/4" in from the bottom edge and the right edge.

Mark 1/8" in from the left edge.

Cut out the 1 1/4" by 1/8" rectangle on the top left and the 1 1/4" by 1/4" rectangle from the top right. Cut out the 1/8" by 1/4" rectangle from the bottom left and the 1/4" by 1/4" rectangle from the bottom right.

Mark 1/4" in from the top edge.

Mark 1/8" in from the right edge.

Using the straight-edged mandrel and the ruler, fold the top 1/4" over into a U-shaped channel. Set the kettle body aside.

Next, you must prepare the kettle body lip which will be attached to the kettle body. It serves to prevent the lid from being jammed on too tight, as well as to form as tight a fit as possible around the lid.

Subtract two times the seam allowance from the body width. In this example, subtract 1/4" (2 X 1/8") from 12 7/16". The resulting width of 12 3/16" is the width for the kettle lip.

Cut out a piece of .022" copper plate 12 3/16" wide by 1 1/4" tall.

Mark 1/4" in from the top (long) edge.

Fold the 1/4" edge over to form a U-shaped channel.

Gently tapping the U bend, close the gap to form a folded lip. It is best to hammer to the inside of the lip, not right on the edge. Do not flatten the edge, leave it as a stronger 'open bend'.

Before you can fit the lip to the body, you must be clear on which piece is the inside vs. the outside. On the kettle body, the inside is flat, the outside has the U-shaped fold sticking up. On the body lip, the outside is flat, and the inside has the extra thickness of the folded lip.

Orient the body lip on the kettle body. The body lip piece's inside surface will face the kettle body's outside surface. The body lip's folded edge will be towards the bottom of the kettle, and the unfolded upper edge will slip under the U-shaped channel on the kettle body.

The lip piece should slightly overlap the side edges of the kettle body. Let it overlap about the same on each edge.

Hammer down the U-shaped channel on the kettle body so that the body lip is pinched.

Apply safety flux (lead-free) to the pinched edge, and solder with lead-free solder or pure tin.

Kettle Lip— Detail showing the kettle lip and its orientation with the side seam fold. (The top of the kettle is at the bottom of the picture.)

Punching the Side Seam— The seaming tool is being used to punch the side seam. Note that the kettle body lip does not have a seam, the edges simply overlap

Coax the kettle all the way onto the mandrel. It should go on easily right up until the last ¼" or so, where the extra stiffness of the lip wants to bind. Tap the edge of lip with the rawhide hammer all around the pot rim. This will true up the circular shape of the kettle’s mouth and allow the kettle to slip all the way onto the mandrel.

Remove the kettle and place it on the mandrel top first, allowing the bottom to overhang the pipe end by ¼" (as marked on the kettle bottom.)

Using the rawhide hammer, hammer over the bottom ¼" of the kettle against the ¼" wall of the pipe to form a 90° degree angle. If you are using new half-hard copper sheet, it will take this bending without cracking.

If more than ¼" was folded over in some spots, simply file it off against the inside wall of the pipe. The final bottom should have exactly ¼" all the way around.

Forming the Bottom Lip— The bottom 1/4" of the kettle body is bent over the pipe. The pipe that you select for a mandrel must have a 1/4" wall. Note that half-hard sheet copper will take this bending without cracking.

The bottom of the kettle is fitted in with a cramped seam (little dovetails) as follows:

Using the drawing compass, scribe a circle on the .022" copper. The diameter of the finished circle should be the same as the outside diameter of the mandrel. For our example, set the compass to 1 7/8".

Cut out the circle.

Draw another circle inside the first with a radius ¼" smaller. For our example, set the compass to 1 5/8".

Draw a line through the center of circle.

Draw two more lines at 60° to the first, dividing the circle into six equal parts.

Draw a line dividing each part into equal halves ; this will divide the circle into twelve equal parts.

On either side of the marks, cut dovetails as shown in the illustration below. (A pattern of only six dovetails is shown for clarity). Avoid the temptation to cut the tabs too deep or you will leak a lot of tin when you get to the tinning stage.

If you wish to mark your kettle by punching your name or mark on the bottom, now is the best time to do it. The outside is the side without the lines scratched on it.

Using needle-nosed pliers, bend the tabs up 90°.

Test the fit of the bottom on the kettle. It should be very close to perfect. You may need to adjust a few tabs to get the bottom to nestle just right.

From the inside of the kettle, bend the tabs back over the bottom lip. Place the kettle back on the mandrel and go around the bottom with the rawhide hammer, pinching everything nice and tight.

You have now completed forming the kettle body.

Attaching the Bottom— Bend the tabs back over the bottom lip of the kettle and then place the kettle over the mandrel and hammer around the bottom edge to clamp everything tight. Note that dovetails are on outside of kettle.

The next task is to form the lid. We begin with the lid sides.

Cut a piece of .022" copper 1 5/16" wide and an inch longer than you need to go around the kettle rim.

Wrap the copper strip around the kettle rim. The correct spot is just below the soldered part of the rim. (Don’t wrap it around the wider lip 1" below the rim). The overlap along the length of the strip should not exceed about 1". Mark the exact length. For the example kettle, the length marked should be around 12 ½".

Add three times the seam width, plus 1/8" for ease, to the measured length. For the example, it should be about 13".

Mark along the bottom edge of the strip ¼" in from the edge. Mark ¼" in from the right side and 1/8" in from the left side.

Cut out the ¼" by ¼" rectangle and the 1/8" by 1/8" rectangle.

Using the straight-edged mandrel, fold the bottom ¼" over and hammer it down on the other side. As with the body lip, don’t flatten the copper completely, just bend it enough so that the edge touches the other side.

Identify the outside and the inside of the lid sides. The inside is flat. The outside has the folded edge on it.

Bend the seam tabs as with the kettle body. Looking at the outside of the lid side, the 1/8" wide seam tab should bend down, and 1/8" of the ¼" seam tab should bend up to form two U-shaped channels.

Using the large pipe mandrel, bend the lid sides and hook together the seam channels. Using the 1/8" seam tool, punch the seam.

Test the fit of the lid sides on the kettle. It should go on and off easily.

Measuring the Lid Sides— Wrap the side piece around the kettle top and mark in the manner shown above.

Extra Lid tops— Extra lid tops act as spacers so that you can get the lid just the right size. Save these spacers for the next time you wish to build the same size of kettle.

The Bail Lug— The shape of the bail lug.

The Bail — The bail is attached to the kettle with two bail lugs. Note the rivet washer on top of the bail wire. Also, the bail rivet does not go through the kettle.