Octagonal Picnic Table

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This article is from Issue 58 of Woodcraft Magazine.

Build the ultimate venue for outdoor dining.

Overall dimensions: 913⁄4"w × 29"h

Family members and friends will enjoy the good times around this accommodating outdoor project that seats up to eight happy diners. There’s nothing tricky about the construction. Plugged exterior-grade screws and waterproof glue bond the 2-by parts together, guaranteeing years of use. A hole at the tabletop’s center allows you to insert an umbrella to shield diners from intense sunlight. The chevron-shaped benches attached to the cross supports allow for easy-access seating, unlike standard picnic table designs, which force you to climb over the seats to sit down. For plans for the complementary lazy Susan, see page 44.

Note: To protect against rot and insects, I used western red cedar. Other outdoor wood choices include redwood, cypress, and pressure-treated pine.

Use a backsaw to cut the notch shoulders, guiding off the layout lines on both faces of the workpiece.

Use a chisel to even up the bottoms of the notches, ensuring that depths equal one-half of the part widths.

Tap the spacers against the intersecting seat and table frame parts. Make them flush along the edges of the frame pairs.

With the bottom ends of the parts aligned against a backstop, strike a reference line along the top end of the seat leg and across the face of the table leg.

Build the cross frames

Note: Before building, take a minute to inspect your stock and select the best boards for each section. Any chips, knots, or bad spots should be kept on the underside faces or cut out when laying out parts. Any crowned faces should face up once fastened in place to better shed water. The most visible parts, or those that will be in contact with arms and legs, must be smooth and splinter free.

1 Now, working with either dimensional lumber or thicker stock that you joint and plane to the part thicknesses in the Cut List, crosscut the left and right seat frame parts (A) and left and right tabletop frame parts (B) to length. Also, cut the eight spacers (C) to size. (See Figure 1 for reference.)

2 Lay out the centered notches on both faces of the seat frame parts (A) and tabletop frame parts (B), where shown in the Detail in Figure 1. (Here, measure the thickness of the combined frame parts and spacer [C] when sandwiched together for the notch widths. The mating notches must fit snugly.) Make the shoulder cuts as shown in Photo A. Then make multiple cuts between the shoulder cuts to the baseline of the notch. Cut out the waste with a chisel and mallet. Repeat for the other notches.

3 At the mitersaw, bevel-cut the ends of the left and right seat frame parts (A) and left and right tabletop frame parts (B) at 671⁄2°, referring to Figure 1 for the bevel orientations.

4 Working on a flat surface such as a workbench, group the left and right frame parts (A) and the left and right frame parts (B), orienting each group with their notches up. Align the part ends, and clamp them together and to the workbench. Clean up the notches, as shown in Photo B.

5 On a level surface, test-assemble the interlocking seat (A) and table (B) cross frames, fitting spacers (C) where shown in Figure 2 and as shown in Photo C. Disassemble.

6 Use exterior glue in all of the joints. Reassemble the frame parts. Mark the screw-hole locations, and drill counterbored pilot holes. Starting at the mating notch joints, drive four exterior-grade 3" screws vertically to join the seat and table frame pieces (A and B). Drive 3" screws through the frame sides and into spacers (C). Repeat for all spacer joints.

Align a seat leg to a seat base on a benchtop as shown, clamping the assembly to the bench. Then drill counterbored holes, and drive the screws.
Apply glue, and set the base assembly on the table leg. Center and align the leg on the seat base between matching spacers. Drill the holes and drive the screws.

Set aside the base assembly with its alignment stops while spreading glue on the hard-to-get-at mating surfaces of the seat frames.

Cut the parts and assemble the seat bases

1 Using 11⁄2"-thick × 51⁄2"-wide stock, cut the table legs (D), seat bases (E), and seat legs (F) to length and at the angles shown in Figure 2.

2 Place a seat leg (F) on a table leg (D) aligning the bottom ends using a backstop, as shown in Photo D. Strike a reference line on the table leg. This will come into play in Step 4 and again when attaching the seat cross frame later. Similarly, strike lines on the remaining legs. Continue the lines across the edges and opposite faces of the table legs.

3 As shown in Photo E, fasten a seat base (E) to two seat legs (F) using three 3" screws per leg driven into counterbored holes. Note that the seat legs should be flush with the ends of the seat bases, as shown in Figure 1. Repeat for all four seat base assemblies.

4 Make a pair of angled seat base spacers, as shown in Figure 2. Next, clamp a table leg (D) in your bench vise with the top end down, aligning the reference lines with the surface of your benchtop. Now, using the spacers, fasten a seat base/seat legs assembly (E/F) to the bottom end of the leg with 3" screws and exterior glue, as shown in Photo F.

Mark and counterbore three centered holes in the joining parts and drive the screws. Repeat to make the remaining three base assemblies (D/E/F).

5 Cut eight seat cleats (G) to size, and glue and screw them with 21⁄2" screws to the inside faces of the seat legs (F). Extend them 7⁄8" beyond the outside edges of the legs, and make their top edges flush with the leg top ends.

Check the alignment of the mating assemblies by placing a straightedge across the top ends of the seat legs and top edges of the seat frames.

Add the base assemblies to the seat cross frames

1 Strike lines 133⁄4" to strike in from the ends across the top edges of the seat cross frames assembly (A/C). This line tells where the table legs (F) intersect the top edges of the seat frames assembly.

2 Clamp a pair of scrap alignment stops along the top of the reference lines on the sides of a table leg (F). Dry-fit the leg of the base assembly (D/E/F/G) in place between the seat frames (A), aligning the reference lines and resting the stops on the top edges of the frames. Next, mark the screw locations on the outside face of one seat frame. (As before, I made and used a plywood marking jig for this.) Slide the base assembly out of the way, and apply glue in the base assembly/seat frames mating area, as shown in Photo G.

3 Slide the base assembly (D/E/F/G) into place, as shown in Photo H. Once all the key parts align, drill counterbored holes for 3" screws. Repeat the process for attaching the remaining base assemblies to the seat frames cross assembly (A/C).

Hold the biscuit marking jig fence along the outside edge of the perimeter boards to mark consistent biscuit slot centers with a pencil.
While firmly holding a perimeter board in place, align the biscuit joiner centerline with the mark, and plunge-cut the slot.

With the assembly jig clamped to the table and one perimeter piece clamped to its fence, glue and screw the top perimeter boards end to end.

Form the tabletop perimeter frames

1 Set up your mitersaw to 221⁄2° (once cut, the miter angle of the board will be 671⁄2°). Verify the angle with a test cut. Using a stop to establish consistent lengths, angle-cut the top perimeter boards (H) and the bottom perimeter boards (I) to length. See Figure 2.

2 Using a square, or with a shop-made marking jig as shown in Figure 3 and Photo I, mark the biscuit locations on the ends of the perimeter boards (H, I). Note: All top perimeter boards receive biscuit slots; only the mating ends of the bottom perimeter board pairs receive slots.

3 Adhere a 3⁄8"-thick spacer to your biscuit jointer with double-faced tape, and cut biscuit slots that are centered on the thickness of the top and bottom perimeter boards (H, I). Align the centerline of the tool with the marks made in Step 2. Cut the slots, as shown in Photo J.

4 Build the perimeter frames assembly jig in Figure 4 using scrap plywood and solid stock.

5 Drill pocket holes on the bottom faces of the top perimeter boards (H) at the ends to fortify the biscuit joints and to snug up the pieces during assembly. Position the holes at least 3⁄4" in from the edges. Be sure the hole locations do not cause the screws to exit the edges of the perimeter boards. Now, working on a large, flat surface, apply glue in the slots, insert the biscuits, and place two top perimeter pieces bottom faces up in the assembly jig. Drive the pocket screws to snug the joint. Move the assembly and fasten another perimeter board, as shown in Photo K. Fit a spacer under the cantilevered end of the assembly to keep it level. Add a fourth board to make one-half of the octagonal top perimeter frame. Build the other half. Let the glue set up.

6 Drill two pocket holes on the bottom faces of the non-mating ends of the bottom perimeter boards making up the four chevron-like frame sets. Use the assembly jig to glue up the sets. Set the four frame sets aside to let the glue cure.

7 Next, glue and screw the two half frames together to make the octagonal top perimeter frame. (I used a strap clamp to help tighten one half frame against the other.) After the glue sets up, remove the strap.

Attach the tabletop cross frames assembly

1 With the octagonal perimeter frame (H) top face down on a large assembly surface, place the tabletop cross frames assembly (B/C) on the octagon’s bottom face. Insert and clamp scrap 11⁄2"-thick leg spacers between the tabletop frame parts to fix their overall dimension for installing the chevron-like bottom perimeter board sections (I). Center the tabletop cross frames assembly on the octagonal frame, as shown in Photo L. Mark the locations.

2 Now, using pocket screws and glue, secure the chevron-like bottom perimeter board (I) sections to the tabletop cross frames assembly (B/C), as shown in Photo M. Use 21⁄2" screws in counterbored holes to fasten the board sections to the octagonal frame (H). Remove the leg spacers.

Cut and install the tabletop boards

1 Solicit a helper to flip right side up the tabletop and top cross frames assembly. Now, measure and cut to length the tabletop boards listed in the Cut List and seen in Figure 2.

For the best results, measure, cut, and fit the outside tabletop boards (J) flush against the octagonal perimeter frame (H). Lay the outside tabletop boards in place.

2 Next, measure the distance between the outside tabletop boards (J). Subtract from that measurement the combined widths of the remaining tabletop boards (K, L). Divide the remaining number by six to determine the spacing between the tabletop boards. Plane or resaw several spacers at that thickness. (My spacers measured 3⁄8" thick.)

3 Angle-cut one end of the outside adjacent tabletop boards (K), leaving the other ends long. Fit the spacers between the outside tabletop boards (J) and the outside adjacent tabletop boards. Mark the square ends of the boards for a good fit and angle-cut them. Lay them in place.

4 Cut three center tabletop boards (L) to fit. Angle-cut the corners of outside center tabletop boards as needed to maintain the spacing.

5 Using the spacers, fit the tabletop boards in place, and drill counterbored holes in the ends (two holes per end). Apply glue, and drive 21⁄2" screws to fasten them to the chevron-like bottom perimeter board sections (I).

Check the distance from the octagon’s corners to the ends of the tabletop cross frames to center the latter. You want the same length all around.
Working a quadrant at a time, glue and screw the chevron-like bottom board sections to the top cross frames assembly and octagon.

Drill counterbored pilot holes through the table frames and into the table legs. Drive screws to firmly fasten the legs in place.

Add the base and seats

1 With helpers, flip the tabletop and attached cross frames assembly upside down. Mark the center of the tabletop cross frames opening on the bottom face of the center tabletop board (L). Drill a small pilot hole through the board. Next, saw a 11⁄2 × 11⁄2 × 36" piece of scrap.

2 Apply glue on the inside faces of the ends of the table frames (B/C). Carefully lift the base assembly, turn it upside down, and fit the table legs (F) between the (B) members of table frames. Insert the 11⁄2"-square piece into the center openings of the frames to align the seat frames over the table frames. Remove the 11⁄2" piece. Now, counterbore holes, and drive 3" screws to secure the base to the tabletop, as shown in Photo N.

3 With helpers, flip the entire octagonal picnic table right side up and set it on a flat surface. Using a 11⁄2" Forstner bit, bore the umbrella hole, guiding on the pilot hole drilled in Step 1. 

Lay out the seat parts (M, N) to the sizes in the Cut List and as shown in Figure 2. Cut the pieces. Finally, using the same spacing for the tabletop boards, fasten the seat parts to the seat legs and cleats (F, G), using glue and 21⁄2" screws in counterbored holes.

4 Cut plugs from cedar scrap. Then, glue the plugs in place to cover up the hardware. Flush-cut the plugs, and plane or sand them even.

5 Sand the octagonal picnic table to 180 grit. Using a 1⁄4"-radius round-over bit in a handheld router, round over the umbrella opening and all exposed seat and table edges. Wipe the surfaces clean and finish. (I sprayed on Sikkens Cetol SRD.)  


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