46 - Utility Workbench, страница 22
A quick way to cover the sharp edge at each corner of the cover is to stick on a small strip of aluminum tape.
The most noticeable thing about this bench top is its metal cover. But what you don't see is what's underneath the cover — a large top piece made from 3/4" MDF, see Fig. 8. It's this top piece that ensures a flat, stable work-surface that won't warp or twist with changes in humidity.
METAL COVER. But before cutting the top piece to size, it's best to have the metal cover in hand. Making this cover should be a routine process for a heating and air conditioning company. All you'll need to provide are the gauge (thickness) of the metal and the final size of the top piece. (My cover is made from 24 gauge metal and is sized to fit a 263/4M x 68" top.)
FOLDED EDGES. To avoid getting cut on a ragged burr (and to add rigidity to the metal), the edges of the cover are first folded underneath, see Fig. 8a. Then these double-thick edges are bent at a 90° angle.
TOP PIECE. Once you have the cover back in the shop, you can cut the top piece (T) to size. To "ease" the fit, I cut it Vb" smaller than the inside dimensions of the cover. Also,
rounding over the top edges and softening the corners allows the cover to fit down over the top piece without wrinkling the metal.
Before attaching the cover, you'll need to screw the top piece to the bench. Then simply secure the cover with strips of carpet tape to keep it from lifting off the top piece.
CORNERS. Finally, the corners of the cover still need some attention. That's because there's a "flap" at each corner with an exposed edge that's quite sharp. You can cover this i edge with aluminum tape, see margin. Or for a more permanent solution, you may want to solder the corners, see the box below.
Soldering the Corners
It only takes a few minutes to solder the "flaps" on the corners of the metal cover.
SURFACE PREPARATION. To ensure a strong bond, the surface needs to be clean. But often, there's a greasy film on the metal. A bit of work with silicon-car-bide sandpaper quickly removes the film.
FLUX. The next step is to brush a thin layer of flux across the joint, see photo below left. The flux will make the solder flow smoothly into the joint.
HEAT METAL. After applying the flux, sweep a propane torch back and forth until the metal is hot, see center photo.
22 ShopNotes No. 46
SOLDER CORNER. You'll know it's hot enough when you hold the solder against the metal and it begins to melt, see photo below right. Ideally, the solder should run evenly along the joint line. But most likely there will be some small gobs of solder that will need to be filed smooth.
POSITION TOP PIECE FLUSH WITH BACK AND CENTERED FROM SIDE TO SIDE /
#0 x V/z" Fh WOODSCREW
PIECE IS MADE FROM MDF