Mounting Legs made of aluminum tube is involved in such projects as the dining-room table of Fig. 8-1 and the sawhorse of Fig. 6-1. The only unusual operation is angle drilling. Most tables use leg angles of 7° to 10° from the vertical. The saw-horse requires a 30° angle.

Do not attempt to drill these holes with a brace and bit. Always use a drill press.

Most have flat beds, and drill vertical holes only. To drill at an angle, a fixture is needed. Make angle blocks for such a fixture as follows:

Take a scrap piece of 1" x 2" wood, and screw through it into the end of a 10" to 12" length of 2 x 4. Fasten this to the miter gauge of a bench saw with a C-clamp as shown in Fig. 4-55. Set the miter gauge to the angle desired. Advancing the assembly to the blade will make the cut wanted as shown. Cut two blocks in this manner, and screw them along the sides of a 12" x 12" piece of V-i" plywood. Figure 4-56 shows a 30° fixture of this type clamped to the bed of a drill press ready for use. Make the 7° and 10° fixtures the same way.

Mark on the surface of the work the exact center of the hole desired. Then spot the work in position accurately under the drill, and clamp it to the fixture with C-clamps as in Fig. 4-57 (a 10° fixture).

Measure depth of hole desired, and set depth stop on drill press. Clamp work securely to avoid wobble and enlargement of hole.

Fig. 4-55.

Use drills of the type shown in Fig. 4-56, of same diameter as tube for leg. After drilling, lubricate the tube with paraffin block or old candle before inserting. Rub lubricant lengthwise of the tube at ;to ;intervals around the circumference. Clamp the drilled wood securely in a vise. Insert tube with a screwing motion while pushing it into hole. Always turn tube in same direction .... clockwise is usually most convenient. Before inserting mark hole depth on tube so you can tell when tube has bottomed in hole.

Fig. 4-56.

Fig. 4-57.

Lock tube in place by drilling through edge of plywood squarely into tube and through it from one side or down at an angle. Then drive in a finishing nail long enough to go through tube and into wood on other side. Use a drill of the same diameter as the nail.

To obtain sufficient hole strength, depth of liole should be 11/2 to 2 times the diameter of tube. Add plywood blocks where necessary. Following are recommended minimum hole depths and thickness of plywood blocks suitable for attaching legs to underside of a table top (if you drill part way into table top, reduce block thickness accordingly) : For 3/4" diameter tube, use 11/4" deep hole (one 1/2" plus one thickness of plywood) ; for 1" tube, ;hole (two 1/2" plus one 3/4" plywood) ; for 11/4" tube, 21/4" hole (three plywood). Nail plywood together with finishing nails to get total thickness indicated. Make blocks to a width 3 to 4 times tube thickness, a length 5 to 6 times. Drill the hole off center lengthwise so about two-thirds of the block extends in a direction opposite the leg (see Figs. 4-58 and 4-59).

Where two pieces of tube are used to make a single leg, as in the dining-room table of Fig 8-1, mount each tube in a separate block at a 7° angle and lock in place. Then position block on a flat surface, and cut off leg to height desired, making this cut horizontally.

Fig. 4-58.

To locate legs correctly under the table corner, use a jig (Fig. 4-58) made from two pieces of scrap plywood 12" to 18" wide nailed to a small block to form a 90° angle as shown. Be sure bottom edges of plywood are square to the vertical joint.

Turn table top upside down, and position jig on a corner 1" (or 2") inside table edges. Position the two blocks so leg tips come together inside top corner of jig and so the two legs form 30° angles as in Fig. 4-59. Now put screws down through predrilled holes in the blocks and into the underside of the table top. Bolt legs together at tips by drilling down through open end of one leg.

Flattened-Tube Connections

End-to-end connections, T-connections, and X-connections are simple to make by flattening the tube at the connection and riveting or bolting members. Flatten the tube in a vise .... do not hammer flat.

Flattening the tube provides a surface easily connected to angle, bar, or rod or for screwing to a wood member, as well as tube-to-tube connections. Figure 4-60 shows how one leg of an angle can be slotted or cut away to make a passage for a flattened tube connection to the inside surface of the other leg.

Slotted Tube Connections

Saw a slot into tube lengthwise. Flatten out split portion to form fingers which will go on either side of a tube, bar, or rod, to which it is attached by bolt, pin, or rivet as shown in Fig. 4-61. Or self-tapping sheet-metal screws can be used when connecting tube to tube. Joint will swivel if only one connector is used. Two or more will make joint rigid.

Flatten the inside tube and flatten the split outside tube just enough to go on either side of the first tube for another simple type of slotted connection.

Sup Joint

To connect two pieces of same size tube end to end, cut a third piece of tube 4" to 6" long to act as an internal "sleeve." Cut a 3/8" wide slot the entire length of this sleeve, as at "B" (Fig. 4-62). Squeeze the piece so the cut edges touch, reducing outside diameter of sleeve so it will slip inside the ends of tubes to be joined. Secure sleeve to one tube with a self-tapping sheet-metal screw.