Follow these instructions to make a hexagonal post from a 2 by 4.
You need a straight 2 by 4 and a table saw. A planer or jointer will be helpful if you have one.
Step 1: Prepare a Blank
Cut a 2 by 4 in half or into fourths. Mill the pieces on a planer or jointer to get all four sides flat and square. A table saw will do if you don't have a planer. Rip and/or plane the pieces to a 2-3/4” by 1-3/16” cross section. Be accurate.
If you want a hole down the length of the hexagonal post cut a dado along the middle of two pieces - on the 2-3/4” wide face.
Glue two pieces together. Use Titebond III or another waterproof glue for outside applications. The resulting piece will have a cross section of 2-3/4” by 2-3/8”; with an optional rectangular/square hole down the middle.
Step 2: Cut the Hexagon Shape
Set your table saw blade at 30 degrees. Set the angle as accurate as you can. A 30-60-90 degree drafting triangle might help.
Set your table saw fence to 2-1/16" inches.
Make four rip-cuts as shown to slice four triangles off the corners. Be sure to put the wider 2-3/4” face down when making the cuts. Use extreme caution when making these cuts as the wood is no longer fully supported on the bottom for cuts 3 and 4. Also, the triangular cut-offs may be thrown off if caught under the blade - stand out of the way!
Step 3: Finished
You are done.
The resulting hexagonal cross section will be 2-3/4" in diameter (D) with each side 1-3/8" long. The glue line will be nicely hidden along two of the edges.
Use for a lamp post, table or bench legs, book shelf supports, baluster, candle holder, turning blank, etc. Or slice off hexagons and assemble into .... whatever!
For other diameters D prepare a rectangular blank of D inches by (0.866 x D) inches, and set the fence to (3/4 x D) inches as shown in the last diagram.