Adjustable 3-in-1 Assembly Table

Drop leaves and a built-in jack provide loads of options.

Designer: Ben Svec
Builder: BIll Sands

If your workbench and table saw too often serve as the place you glue up frames, boxes, and other small to medium projects, why not free them up with a dedicated assembly surface? This mobile table, made from two ¾"-thick sheets of MDF and maple trim, provides assembly surfaces in three sizes, with the largest measuring 36 × 51" when both drop leaves are raised. A scissor jack cleverly mounted inside (see Figure 3 on page 23), along with four star knobs, lets you lock in the desired working height from 24" to 36". This adjustable feature also allows the project to function as a precision outfeed table or benchtop power tool stand. When not in use, drop the leaves and roll the table against the wall or below a table saw wing. Note: See the Convenience-Plus Buying Guide on page 26 for the products used in this story. You’ll certainly want the jack on hand during construction.

Build the inner sleeve first

1 Cut the inner sleeve ends (A), sides (B), jack supports (C), and support plate (D) to the overall sizes in the Cut List. Also see the Cutting Diagram.

2 Chuck a 2½" Forstner bit in your drill press and bore holes where shown in the parts view for inner sleeve ends (A) in Figure 1. 

3 Strike lines for the jack slots referring to Figure 3 and cut out the waste as shown in Photo A. Use a rasp or curved sanding block to clean up the sawn slots, then rout a 1/8" round-over along both faces of the slot.

4 Clamp the two jack supports (C) face-to-face, aligning the edges and ends. Mark the location of the centered ¾ × 3½" notches on one face. While the supports are still clamped together, cut the notches in both pieces. Separate the two and test the fit, as shown in Figure 3. Adjust as needed with a rasp.

5 Using a pocket-hole jig, drill five evenly-spaced holes along the inside faces of the inner sleeve sides (B) at the ends, as shown in Photo B, and of parts A and B where shown in Figure 1. Drill pocket holes in one jack support (C) in order to attach it to the inner sleeve. (Don’t own a pocket-hole jig? Join the ends and sides with simple butt joints held together with glue and 5mm × 40mm Confirmat screws. See the Alternate Joinery Detail in Figure 3.)

6 Rout centered and intersecting ¾" dadoes ¼" deep on the bottom face of support plate (D) to fit jack supports (C) where shown in Figure 1.

7 Drill the pilot holes and then screw the inner sleeve sides (B) to ends (A), aligning the top and bottom edges as shown in Photo C. Clamp parts in place to ensure control during assembly and check for square.

8 Center the jack support (C) with the pocket holes (slot up) in the inner sleeve assembly. Use the other slotted jack support (C) to center and secure the piece in place while driving the screws. Ensure that it’s flush with the bottom edges of the sleeve assembly. Now drive the screws. Slip the remaining jack support onto the fixed support. Square the support assembly with the support plate (D) as shown in Photo D and secure it with Confirmat screws. (Note: You’ll need to unscrew the plate later in order to fasten the lower sleeve to the base.)

9 Face-glue and plane enough stock for a 2"-thick block. Crosscut and rip the lamination to 33/8 × 6" for the jack’s top plate (E). Drill a 5/8"- diameter hole ½" deep where shown in the Top Plate Detail in Figure 3. Apply a 3"-wide piece of Slick Strip on the top face. From ¼" plywood scrap, make a 2"-wide spacer (F) like the one in the detail. Insert the lag screw through the jack and spacer and fasten it to the top plate, allowing for a little play when raising or lowering the outer sleeve. 

Bore centered holes for the jack slots through the inner sleeve ends. Cut out the waste with a jigsaw.
Mark evenly spaced pocket holes on the face of the workpiece, and then use the stepped bit to drill the pocket holes.

Using an extended square-drive bit in a portable drill, drive  #8 × 1¼" screws into the pockets and joining parts.

Now build the outer sleeve

1 Cut outer sleeve ends (G) and sides (H) to size plus 1/8" wider than the dimensions in the Cut List. Locate the vertical center of each end (G) and strike a line from top to bottom. Mark the 2½" hole locations on the parts and drill the holes with a Forstner bit. Jigsaw out the waste, smooth the sawn edges, and rout 1/8" round-overs where shown in Figure 2.

2 Chuck a 3/8" straight bit (with a 1" cut length) in your table-mounted router, raise it ¼", adjust the fence to cut the slots in the ends (G) where shown in Figure 2. Next, mark the locations of the bit edges on the fence and the top and bottom ends of the slots on the workpiece. Turn on the router, align the left-hand slot reference line with the left-hand bit location reference line, and lower the workpiece onto the bit as shown in Photo E. Move the workpiece from right to left until the right-hand slot line and bit line align. Do this for all four slots at this time. Now, remove the workpieces, raise the bit another ¼", and repeat. Raise the bit again until you’ve cut through the workpieces, creating all four slots. 

3 Apply ¾"-wide adhesive-backed Slick Strips 1" in from the inside edges as shown in Photo F, and a second set 3¼" in. (See Figure 2.) The strips allow the outer sleeve to easily slide over the inner sleeve when raising and lowering the jack.

Locate the dadoes of the support plate onto the jack supports. Lock them in place with Confirmat screws.

With the workpiece snug to the fence, lower the outer sleeve ends over the hidden bit using the alignment lines as a guide. Well-placed reference lines for the bit edges and slot ends let you accurately rout matching slots.

4 Clamp the outer sleeve ends (G) to the inner sleeve, aligning the jack slots. Hold the sides (H) to the ends and mark the cutline for trimming the sides to exact width as shown in Photo G. Trim the sides to finished size. 

5 Drill pocket holes along the ends of the outer sleeve sides (H) on the outside faces, then vertically apply 3"-wide Slick Strips to the inside faces 1" in from the edge. (See Figure 2.)

6 Fit outer sides (H) snugly against the inner sleeve and clamp them in place, flushing the bottom edges on a flat surface. Now, drive the pocketscrews. Undo the clamps, and slide the fastened outer sleeve up and off the inner sleeve. (You may need to clamp a caul across the top of the outer sleeve and use the jack to raise the sleeves.) With the two sleeves separated, apply a liberal coat of wax to the outside faces of the inner sleeve. 

7 With the outer sleeve upside-down on a bench or table surface, cut biscuit slots to accommodate the tabletop fasteners used to hold the top in place as shown in Photo H. Use a tabletop fastener to determine the distance from the top edge for the biscuit slots. Ours measured 5/8".

8 Adhere a ¼"-thick length of scrap plywood to your router-table fence for clearance, chuck a flush-trim bit in the router, adjust the fence for a clean flush-trim cut, and rout the waste from the outer sleeve ends (Photo I and Inset). 

9 Cut two leaf supports (I) to the size and shape in Figure 2. Using a router table and straight bit or dado blade, cut a ¾"-plus groove ¼" deep in a ¾ × 2 × 12" piece of maple. From it, cut two 2"-long support cleats (J). Drill screw holes in the cleats. (See Figure 3.) Set both I and J parts aside for later.

10 Make the crank handwheel (K), handle (L), and shaft (M) for the crank assembly using the dimensions in the Cut List and Figure 3. Drill the holes and glue the dowel handle into the handwheel. Handsaw intersecting kerfs at the corners  ¾" in from one end of the square shaft and drill a countersunk ¼" hole through the length. Set aside. 

Press the Slick Strips in place with a laminate roller or a block of wood, bevel-cutting the ends.
Hold the outer sleeve sides to the clamped ends to get a precise width measurement. 

Place a ¼" spacer below the tool’s base and adjust the cutter for a #20 biscuit slot. Make the cut.

Place the outer sleeve on the router table and trim off the waste along the edges with a flush-trim bit. 

Construct the wheeled base

1 Crosscut a 24½" piece of MDF from one end of a full sheet. Next, crosscut that piece into two pieces that roughly measure 24½" square. (See the Cutting Diagram.) Now, apply glue to the mating faces and face-join the two squares together, aligning factory edges. Clamp and weight the pieces together and let dry. 

2 Working from the factory edges, cut the workpiece square on the table saw, trimming all four edges to achieve a 24"-square part to create the base (N).

3 Rip enough maple stock for the base side and end bands (O, P) to 15/8" wide. Now cut, glue, and clamp the pieces along the edges using butt or miter joints as desired. Once the glue dries, flush-trim the edges of the bands with the base. Rout a 1/8" round-over on all maple edges.

4 Place the casters just inside the bands (O, P) on the base (N) and mark the hole locations for the hardware. Drill the holes through the base, but do not attach the casters at this time.

5 Place the base assembly on a work surface. Now center and clamp the inner sleeve to the base and screw it in place as shown in Photo J, using the pocket holes drilled earlier.

6 Slip the outer sleeve over the inner sleeve, flush the top edges, and clamp it in place. Now, drill 5/16" holes through the inner sleeve, using the top end of the 3/8"-wide slots as a guide. Insert 2½" carriage bolts through the holes from the inside, and then add 5/16" fender washers and star knobs. Tighten the knobs to sink the carriage bolt heads into the MDF.

To prevent bulging the inner sleeve, secure it to the base with clamped cauls. Remove plate (D) to access pocket holes.

Add the top, leaves, and leaf supports

1 Crosscut the remaining piece of MDF into two equal 3'-wide halves. Apply glue to both mating faces and clamp and weight the pieces together, flushing the factory edges. (Refer to Figure 3 and the Cutting Diagram.) As with the base, use the factory edge to rip the panel to 35" wide. Now run the long cut edge against the fence and then trim the glue-up to a finished width of 34½".

2 Set your table saw fence 15/8" from the blade and rip enough ¾"-thick maple band material for all four edges of the top (Q) and two leaves (R), cutting two of the pieces to 50" long. Center, glue, and clamp the 50"-pieces to the long edges of the glue-up panel. Once dry, flush-trim the maple and flush-cut the waste from the ends of the maple bands.

3 Using your table saw and miter gauge with an auxiliary fence or a circular saw with a straightedge, cut one end of the banded panel to 11¾" wide and set aside. Next, cut the top (Q) to 24" wide and set it aside. With the remaining piece, cut one of two leaves (R) to the final 11¼" width, running the long sawn edge against the fence. Doing the same, return to the 11¾"-wide piece and trim it to final width for the other leaf (R).

4 Cut the six remaining pieces for the top and leaf end bands (U), glue and clamp them in place, and flush-trim as described before. Label the top surface for the top and leaf assemblies.

5 Ease the hard edges of the top and leaf assemblies, except where the hinges attach, with a handheld router and 1/8" round-over bit.

6 Cut the continuous hinges to 35¾". Place the top and leaves bottom face up on a flat work surface. Place  1/16" spacers between the leaves and top (to provide clearance for the leaf supports [I]), align the edges, locate the hinge, and drill pilot holes for the screws. (We used a Vix bit to ensure centered holes.) Now drive the screws as shown in Photo K. See Figure 4 for reference.

7 Drill four holes at the corners through the base of the jack. Bolt the jack and accompanying top plate (E) to the support plate (D). Now, using a helper, turn the sleeve and base assembly upside down and centered on the top assembly. Insert the tabletop fasteners in the biscuit slots and screw them to the top as shown in Photo L.

8 Carefully attach the cut-off pieces of continuous hinge from Step 7 to each leaf support (I) exactly as shown in Figure 2. Strike a vertical line 7¼" in from one edge of the outside sleeve on parts H. Retrieve a support cleat (J) and fit it on the outside top edge of one leaf support (I). Rest both parts on the bottom face of the leaf (R) and align the unhinged face of the leaf support with the vertical line. Drill the pilot holes and drive the screws. (When the leaf supports are folded, you want the outside ends to be flush with the corners of the outer sleeve.) Repeat this procedure for the other leaf support, offsetting it to the diagonal corner.

9 Screw the centered support cleats (J) in place on the leaves (R). 

10 Install the casters to the base with carriage bolts, washers, and nuts, and then solicit a helper to carefully stand the assembly table upright on the floor.

11 Chisel a 15/16"  square mortise  3/8" deep in the handwheel center and drill a centered 1/4" hole in it. Glue the unkerfed end of the square shaft (M) into `handwheel (K). Next insert a 3"-long ¼-20 flathead machine screw through the kerfed end of the square shaft (M) and that end into the square opening in the jack. Add the washer, tighten the nut, and hacksaw the screw to length. Cut a screwdriver slot in the cut-off end of the screw. By tightening the nut, you’ll spread the shaft in the jack opening, locking it in place. You may need the slot to hold the screw while tightening the nut. Now give your completed assembly table a test ride up and down. Provide a clear finish if desired. 

Avoid stripping out the screw holes by using a manual screwdriver to drive the hinge screws.
With the outer sleeve centered on the top assembly, screw the tabletop fasteners in place. 

About Our Builder/Designer

Designer: Ben Svec’s contributions to Woodcraft Magazine also include the A-Frame Mobile Clamp Rack (Feb/Mar 2009) design, and four projects he designed and built, the latest being the Heirloom Pendulum Cradle and Pendulum Doll Cradle (Oct/Nov 2008). Ben operates Falls Millwork, a small custom furniture and cabinet shop in Kelley, Iowa.

Builder: Retired research technician Bill Sands spends a lot of time in his Parkersburg, West Virginia, workshop (featured in the Dec 08/Jan 09 issue), teaches hand tool and joinery classes at the local Woodcraft store, and instructs the West Virginia University-Parkersburg wood technology class.

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