| Demilune Table -- Veneer Tabletop |
From "Wood Works"
episode WWK-201 |
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With the tapered legs, curved apron and bridle joinery of the demilune table complete, and the madrone burl veneer pieces cut, work can begin on creating the tabletop. The tabletop (figure A) is actually constructed from a 3/4-inch apple plywood substrate that is covered with cherry veneer on the bottom, and madrone-burl veneer for the top surface. Tabletop Geometry To create the top, a template is fashioned using similar techniques to those used to make the curve apron. To generate the elliptical geometry for the curve of the tabletop, a furniture-maker's technique is used employing a simple piece of string and some carefully thought-out mathematics. - To create the curve, begin with two important dimensions: the long axis and short axis of the table. For the long axis (figure B) measure for the maximum width of the table at the back of the apron -- the overall length of the tabletop -- and add 1-1/4 to the length on both sides to create an overhang for the top. Then measure the width of the table, adding 1-1/4 inch to that dimension as well.
- The curved template is fashioned out of MDF. First, transfer the long-axis measurement onto the MDF. Then, at the center point of that line, transfer the short-axis measurement onto the MDF as well (figure C), forming an upside-down "T."
- Subtract the short-axis measurement from the long-axis measurement to get a working number. Take that working number, and divide it by two. This will yield a reference measurement.
- Using the reference measurement, measure out from the center-point along the long axis to establish a left and right point. Place pins at these points.
- Take a piece of string, wrap it around the pins, and stretch it out to the mark the short axis (figure D) -- forming a triangle. Tie a knot in the string so that it holds the triangle shape.
- Using a pencil at the top of the triangle, put a little tension on the string and swing in one direction to form half of the ellipse (figure E).
- Follow around like a pendulum in the other direction to complete the ellipse (figure F). If done properly, this technique should result in a perfect semicircle with the proper dimensions for the tabletop.
Building the Tabletop With the shape marked on the MDF, the template can be cut. The template will then be covered with sheets of veneer, and the edges banded with cherry strips, to form the tabletop. In this demonstration the assembly is bonded together with the help of a vacuum press. Materials: Cherry stock
Madrone-burl veneer
3/4-inch plywood stock
MDF for substrate
Vacuum press
Jig-saw
Table router
Band saw
Hand saw
Clamps
Pattern-maker's rasp
Wood screws
Yellow wood-glue
Glue roller
Chalk or carpenter's pencil
Safety glasses or goggles
Note: Cut sizes may vary. For exact measurements, please contact David Marks through his Web site -- information below under Resources. Safety Alert: Always wear safety goggles or safety glasses when working with power-tools, saws, drills, routers, etc. Steps: - The tabletop is made from a solid sheet of plywood, cut to the shape of the template, and later covered in veneer. A strip of cherry is glued along the edge of the plywood, and flush-trimmed using the table router. This is done while the board is still square, making it easier to clamp together.
- With the ellipse drawn on the MDF, use a jig-saw to rough cut the template for the tabletop (figure G) and clean up the edges with a pattern-maker's rasp.
- Once the template has been made, it can be aligned and attached to the plywood substrate using wood screws.
- With the plywood substrate prepared, and the template attached, cut the curved form in the plywood using the band-saw (figure H). Save the curved fall-off from the cut (the portion outside the curve), as it will be used later as a form when the front edge of the tabletop is banded with cherry veneer.
- With the substrate cut into its curved form, clean up the rough edges using the table-router and flush-bearing bit (figure I). With the MDF template still attached to the substrate, the bearing follows along the template while the carbide cutter smoothes the edge.
- Apply glue to the edges of the plywood substrate (figure J) to band all of the edges of the plywood substrate with a thin strip of cherry.
- To get good clamping pressure, use the plywood falloff -- from the earlier cut -- as a form (figure K).
- Tip: Raise the plywood substrate with some wood shims (figure L). That will help ensure that the thin strips of cherry will cover the edges of the plywood.
- Using the curved form, clamp the glued assembly securely while the glue dries (figure M).
- After the glue has dried, use a handsaw to cut the cherry banding to proper size. Then, use a scraper to trim the edges of the banding so that it is flush with the tabletop (figure N).
- With the substrate cut and banded, the next step is to use the band-saw to cut the cherry veneer for the bottom of the table and the madrone-burl veneer for the top.
- Using the band-saw, the madrone-burl veneer is cut (figure O) slightly oversized -- so that it extends about 1/4-inch beyond the edges of the plywood substrate.
- With the substrate and the two sheets of veneer cut, preparations are made for assembly and glue-up using the vacuum press. A "sandwich" is fashioned out of the madrone veneer on top, the cherry veneer on the bottom and the plywood in the middle. Glue is applied to both sides of the substrate as well as to one side of each of the veneers. Apply generous layers of yellow glue to each of the surfaces, spreading it evenly and uniformly using a roller (figure P). Be certain to get good coverage along the edges.
- With glue applied evenly on each of the surfaces, put the "sandwich" together (figure Q), making sure that the edges are aligned precisely.
- The assembly is then taped with carpenter's tape at the edges, then placed inside the vacuum press (figure R). The tape prevents the veneers from shifting during the vacuum-press process. Before sealing, a support piece is placed on top of the assembly to help distribute the pressure evenly.
- The vacuum press is then sealed and the pump is turned on (figure S).
- The suction results in pressure of 1500 pounds-per-square foot applied to the assembly (figure T). It takes about two hours at this pressure to bond the veneers to the substrate.
In the final segment of this project, the table is assembled and a wood finish is applied. Sponsored Resource
> Click here to order your tools and materials for this project from Woodcraft!
RESOURCES :
Fine Woodworking
A magazine devoted to high-quality craftsmanship in woodworking.
The Taunton Press Inc.
Website: www.taunton.com
The Small Wood Shop (The Best of Fine Woodworking)
Author: Helen Albert (Editor)
Publisher: Taunton Press
ISBN: 1561580619
Woodworking Techniques: Best Methods for Building Furniture from Fine Woodworking
Author: Editors of Fine Woodworking magazine
Publisher: Taunton Press
ISBN: 1561583456
Mastering Woodworking Machines (Fine Woodworking Book)
Author: Mark Duginske
Publisher: Taunton Press
ISBN: 0942391985
David Marks Website
David Marks, DIY's Wood Works host, is a master woodworker. For more information on cut sizes and project details, please contact him via his Website at www.djmarks.com
The Complete Woodworker's Companion
Author: Roger Holmes
Publisher: Watson-Guptill
ISBN: 0823008665
The Complete Book of Wood Joinery
Author: Robert J. Decristoforo
Publisher: Sterling Publishing Co.
ISBN: 0806999500
Advanced Woodworking
Model: 0783539126
Author: Editors of Time Life Books
1998
Time-Life Books Inc.
Website: www.timelife.com
Popular Woodworking
F & W Publications, Inc.
Website: www.popularwoodworking.com
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