A comprehensive educational community devoted to trim carpentry, finish carpentry and architectural millwork. Hosted by nationally recognized author and finish carpentry specialist Gary M. Katz.
  Tapered Columns  
Craftsman-style or Arts & Crafts bungalows and homes are often identified by the elephant-leg or tapered columns that support their deep overhanging front porches. The first chore is working out the proportions of the columns. The home above was built a few years ago, near the Pasadena area.
A scaled drawing sure helps determine the proportions. A drawing also helps isolate the pieces and the construction/installation procedure. I used butt joints for all the corners. Most exterior trim manufacturers recommend butt joints and won't warrantee mitered joints. On a tapered column, a miter joint will be even more fragile because the material (if it's solid wood) will swell and contract at different rates depending on the width/taper/height of the boards. When a butt joint swells, the pain will crack slightly, but the joint will not open. If the columns have to be mitered (I don't see why they would for a Craftsman-style installation--emphasized joints or eased joints would be more suitable for the style), you could cut lock miters after milling the boards to size.
Like any butt-jointed box, the column is made of two wide outside boards, and two narrower inside boards.
Start by ripping a blank the width of the outside board at the bottom of the column. Then layout the taper at the top. For the home pictured above, I made the columns 14 in. wide at the bottom and 7 in. wide at the top. I marked a center line on the board, then measured back 3 1/2 in. in both directions to mark the taper.

Clamp the board to the sled and hold the front edge of the work piece exactly 2 in. past the front edge of the sled.

The columns in this drawing will be 15 in. wide at the base, and 7 1/2 in. wide at the top. Hold the front edge 2 in. past the front edge of the sled. Using a 2 in cantilever for the outside boards will allow you to use the same sled setup for cutting the inside boards, which will be 1 1/2 in. narrower.
Cantilever the top board 2 in. past the sled, too, measuring to the taper layout line.

This drawing shows the tops of the columns at 7 1/2 in. wide, but the 2 in. cantilever remains the same.



Clamp the work piece to the sled, then attach a fence at the rear edge. Fasten toggle clamps to the fence, too, so the material won't move during the rip cut.

To make repetitive cuts easier, fasten a fence at the bottom of the work piece, too. And attach a piece of 2x4 on edge at the very end of the sled. Using a pushblock makes the operation much safer and the cut much cleaner.
The pushblock keeps your hands away from the blade, especially at the very end of the cut. Don't throw away the fall off. Use that piece to make the second taper cut.
Position the fall off against the fence and slide it forward until the taper layout mark is exactly 2 in. beyond the front edge of the sled.
Save the fall off piece for future cuts, and install a second toggle clamp to secure it against the fence.
After making the first cut, flip the board, insert the fall all piece against the fence, then make the second pass.
For paint grade columns over 11 in. wide, use Extira: a superior exterior grade sheet material available in 3/4 and 1 in. thickness, and in boards 12 in. and 24 in. wide x 16 ft. long, or in full 4x8 and 4x10 sheets. Prime everything before assembly. Assemble three sides of each column at a workbench, using waterproof glue and 1 1/2 in. brads. Then reinforce the joints with stainless-steel trim head screws.
Attach backing at the top and bottom of the columns. The backing should be slightly smaller (about 1/8 in. to 3/16 in.) than the i.d. of the column. Then wrap the rough post. To prolong exterior finish work, and get longer life from paint, always wrap rough framing before applying any exterior trim material. If you don't isolate rough framing from finish material, the moisture content of the rough framing will migrate to the finish material.
Tack the three-sided column to the backing, then install the final side, first with brads and waterproof glue, then reinforce the joints with ss trim-head screws. A little flat trim on the base adds a distinct shadow line.
  Supported by corporations who care about education in the construction industry.  
  Andersen Windows  
  Mastering FInish Carpentry DVDs