| Torsion Box -- Attaching the Top and Bottom Skin |
From "Wood Works"
episode WWK-409 |
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Top and Bottom Skin With the internal grid of MDF constructed, the next phase of the torsion-box project is to add the top and bottom skin of 1/2-inch MDF. Once that is done, the decorative mahogany frame can be added. Materials: 1/2-inch MDF
Table saw
Hand-held router
Pneumatic nail-gun (brad nailer)
Yellow woodworker's glue
Steel-rule straight edge
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 wood, power-tools, saws, drills, routers, etc. Steps:
- Use the table saw to cut the top and bottom skin-pieces from 1/2-inch MDF. Cut the pieces so that they are 1/4-inch oversized. The overhang of the grid will make it easier to position the skins onto the grid during glue-up.
- Use a square and carpenter's pencil to draw reference lines around the frame to ensure that the nails used to secure the skin to the grid will hit their marks. At the point where each section of the grid intersects with the frame, make a center line and extend it down the side of the frame (figure A).
- With the guide marks all made, apply ample amounts of yellow glue to the top of the grid (figure B). Excess glue is not a problem, as it will fill the gaps in the joints, and add to the overall strength of the grid and frame.
- Before setting the first MDF skin in place, put positioning sticks diagonally across each corner of the grid (figure C). These will be used to help position the large MDF top into proper alignment.
- Carefully place the first skin on the positioning sticks and adjust it so that there's about 1/4-inch overhang on all sides (figure D). With the MDF piece in position, pull out the positioning sticks.
- Tack the corners of the MDF to the grid using the nail gun.
- Use a long straight-edge to complete the layout for the nails by transferring the lines from the sides of the frame across the top of the skin (figure E).
- Use the nail gun to fasten the MDF skin to the top of the grid, following the reference lines (figure F). The nails help clamp the skin down, but it's the yellow glue that bonds the skin securely to the grid.
- With the first skin secured, lift and flip the assembly over (figure G). Use a scraper to remove any glue that's dripped onto the flat work surface.
- With the assembly flipped over, apply yellow glue, place the positioning sticks and position the bottom skin as before (figure H).
- Remove the positioning sticks (figure I) and tack the corners with nails.
- Draw on the guidelines for the grid using the steel rule (figure J).
- Once the lines are laid out, clamp the bottom skin in position as before using the nail gun (figure K).
- Allow the assembly to dry for 24 hours, then scrape away any excess glue on the outside of the frame.
- Use a hand-held router and flush-trim bit to trim the overhang from the top and bottom skins (figure L). Flush the edges of the skins smooth with the frame.
Mahogany Frame
With the structure complete, the outside of the box can be trimmed with mahogany for a decorative touch. A hard wood like mahogany was selected since the outside of the table will receive a lot of use and wear from clamps and tools.
- Cut the mahogany stock to size: one pair of boards at 48 inches and another at 61-1/2 inches (figure M).
- Attach the short sides first using yellow glue, evenly applied for a good bond.
- Once the short side pieces are in position, clamp them in place (figure N) and allow the glue to dry for several hours.
- Use the long pieces to the other sides of the box using the same technique.
In the segment that follows the assembly table is completed and given a smooth finish. 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
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
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