DIY Network

Coopered Glass-Top Table: Column Stock From "Wood Works" episode WWK-509

	The thick glass top offers an unobstructed view of the fine craftsmanship used to make this hall table.
	Each coopered column tapers from bottom to top, and the two sections lean inward toward each other to provide dynamic tension and balance.

In this episode of DIY Wood Works, host David Marks builds a contemporary glass-top hall-table with a coopered column-base made of jarrah wood.

Drawing on the skills of craftsmen who built oak barrels for aging wine, this hall table was created with a coopered base consisting of two curved sections. Coopering is the art of barrel-making and involves a process for making curved wood surfaces without bending the wood. Narrow strips of wood called staves are cut to fit together so that they follow the arc of a circle.

To create the curved bases for this table, staves are milled from jarrah wood, and a template serves as a layout guide as we angle-cut each stave to bring the pieces together in a sweeping curve. The top and bottom edges of the barell-like base sections are cut on an angle so the sides of the base tilt gracefully in toward each other. To join the sides, copper pipes -- finished using a hot patina process -- are cut and glued into holes that have been partially drilled through the sides of the base. The cut-glass top gives a bird's eye view of the craftsmanship and allows the beauty of the wood and copper to show through.

Materials:

Jarrah stock
Poplar stock for mockup
MDF for template
Table saw
Jointer
Bevel gauge
Straight-edge
Carpenter's pencil
Chalk
Safety glasses or goggles

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Safety Alert: Always wear safety goggles or safety glasses when
working with wood, power-tools, saws, drills, routers, etc.

Preparing the Staves

• Begin the design process by using a large compass to draw an arc with a 15-inch radius (figure A) to represent the outside edge of the two curved columns.

• Next, reset the compass and draw a parallel line 1-5/8 inches from the first curve. This line will define the thickness of the columns.

• The finished height of the table is 30 inches, including the 1/2-inch glass for the top. As seen in the prototype, the columns will follow the curve of the template (figure B) and will be 18 inches wide at the base. Each is tapered so that they will be 14 inches wide at the top.

  Figure A

  Figure B

  
  

  	Figure C
  	Figure D
  	Figure E

• Using the curved template as a guide, we decided to divide each of the columns into 8 staves, with each stave roughly 2-5/8 inches wide (figure C). This will provide enough stock to cut and fit the staves together. The process of coopering will allow these square-sided staves flow into a graceful curve.

• Note: Rather than using our jarrah stock initially, we created a mockup using poplar blocks to work out the angles of the cuts. It's advisable to make test cuts on inexpensive wood like poplar as you learn this process.

• With the poplar blocks lined up to follow the curve of the template, when the edges line up on the concave side of the curve line up, the edges on the convex side (or back side) of the curve open up with small gaps (figure D). The spacing of this gap is the key to finding the cutting angle.

• To accurately measure the gap, outline the blocks onto the template (figure E), then use a bevel gauge to find the exact angle.
  
• Line the gauge up with the layout line that represents the back side of the stave, and adjust the bevel so that it lines up with the center-line of the marked angle (figure F).

• With the angle determined, match that angle on the table-saw blade (figure G).

  Figure F

  Figure G

  
  

  	Figure H
  	Figure I
  	Figure J

• With the angle set on the table saw blade, make a test cut on a piece of the poplar. Joint the cut face flat using the jointer.

• Back at the table saw, adjust the fence, rotate the stock and make the second angled cut (figure H).

• Joint the second face (figure I).

• Repeat with the other poplar blocks.

• With our poplar pieces cut, we were able to determine that we needed to cut a 4-degree angle on each stave in order for them to fit the curve. Note that the two end-staves only have one angle cut, leaving the outside edges square at 90 degrees (figure J).
  

  	Figure K
  	Figure L
  	Figure M

• With the test cuts complete and the angles worked out, you can now mill and cut your jarrah stock at the table saw. We began with 8/4 jarrah stock, milled it to 1-5/8 inches thick (figure K) and cut it slightly oversized at 34 inches long. (These will be trimmed to final size later when the base is angled and the top is flattened.)

  Note: It's important to keep the stock pieces in order for color- and grain-matching, and because the two end pieces will be left square on the outside edge. Use chalk to number each of the staves from "1" through "8," and note the bottom and top of each stave.

• With the jarrah stock milled to size, rip the 4-degree angles on the staves. First, cut one side on all of the staves. Then, remove the saw-marks and flatten the freshly cut face at the jointer (figure L).

• Next, re-adjust the fence to 2-3/8 inches before making the cuts on the second side of the stock pieces. (This adjustment will allow for the stock that was cut away with the first cut.) Set the jointed edge against the fence and cut the second 4-degree angle on all staves(figure M), excluding the end ones.

• Joint the faces of the stock to remove any saw marks left from the second set of angled cuts.

In the segment that follows, the staves are glued together to form the two curved columns. A special jig is then created to cut the angles on the ends columns allowing them to lean inward, and to support the flat glass-top.