Introduction: Easy Angled Mortises on the Drill Press - (Attaching Round Legs at an Angle)
One of my favorite things to make is wooden stools. I love them for their simplicity and versatility.
When building these I most often use a round tenon in an angled mortise to attach the legs to the top. These joints provide a clean strong connection, and they are easy to make with a drill press, Forstner drill bits and a simple jig.
Step 1: Materials
To start you'll want to gather supplies for the stool and the jig.
For the stool:
1) A wooden top - I'm using a 14" disk made from ash that's 7/8" thick. I've already joined, planed and shaped the circle. This can be any size as long as you can fit it on the drill press jig you build.
2) A set of round legs - I made four of these on a small wood lathe. These are about 14" long with 1"x1" tenon and a 1 1/2" diameter at the shoulder.
For the jig:
3) a 3/4" thick piece of MDF or shop ply that is a few inches larger than your seat diameter. Here I have a 17x17" square and two 1"x17" strips
4) Wood glue
5) 1 1/4" brad nails
Step 2: Tools
Next you'll want to have a few tools on hand
2) Tape measure
3) 12" combo square
4) 18" ruler
5) 45 degree drafting triangle
6) Brad nail gun
7) Forster drill bits: 1 1/2" and 1"
8) Safety glasses
Step 3: Mark the Seat
- First you'll want to mark the wooden top so that it has center lines for reference. This is easiest to mark before you cut the circle. After the circle is cut you can transfer the lines to the side with a combo square. Be sure final marks are made on the bottom side of the seat.
- Next, because of how I want the grain direction to run on the stool I adjust the center lines to 45 degrees from the grain direction using a drafting triangle.
- Then mark the center point for each leg mortise using a combo square set at 3" and drawing a line at that point. You can adjust these points closer to the outside edge for a wider stance.
Step 4: Make the Jig
This jig provides reference surfaces for your piece on the drill press and
this one set up will allow you to cut all the mortices with a simple rotation.
1) Take your 17"x17" piece of MDF and mark the center line at 8.5"
2) At the bottom side draw two 45 degree angles diverging from the center line as shown.
3) Next cut 45 degrees off one end of each of the 1" MDF strips.
4) Then position the 1" strips so the cut angle fits inside the panel at the bottom as shown. Then mark and trim the outside edge of each strip to fit inside the panel dimension.
5) Now you can attach the strips to the panel by applying some glue for tack. You want to be sure the corners line up directly on your center line and set at exactly a 45 degrees. Use your reference lines and your combo square to position them in this way.
6) Finally, pin nail in place.
Step 5: Set Up the Drill Press
1) Start by centering your drill press table. I do this by eye, checking alignment with the base and then the chuck.
2) Then set the angle of the table to the degree required for your project. I'm positioning mine to 15 degrees and you can increase this for a more dramatic angle.
3) Next insert your 1 1/2" bit into the chuck and tighten.
3) Place your MDF jig with the seat onto the table. First, align the center mark on the edge of the seat disk to the center mark on the jig, then position the jig onto the center of the table. You can check that the edges of the jig are parallel to your already centered table and use the brad point of the forstner bit to locate the exact position.
4) Now clamp the jig to the table.
5) And clamp the seat to the jig.
6) With the drill turned off I pull the bit down all the way until it makes contact with the wood and adjust the measure marker on my press to 0. This is simply a reference as I start.
Step 6: Bore the Widest Hole First
1) Now with your set up positioned correctly and securely fastened in place bore the first 1 1/2" hole so that the entire diameter of the bit just clears the surface. On thicker seats this hole can continue deeper for an even stronger hold. For now we just want a even clean connection between the seat and the leg.
2) Note the depth of this hole so that you can repeat this on the next three.
Step 7: Bore the Smaller Hole
1) With the seat and jig still securely fastened remove the 1 1/2" Forster bit and replace it with the 1" bit.
2) Now drill the second diameter hole for the tenon you turned on the lathe. In this instance I'm going to drill as deep as possible without cutting through to the other side, leaving about 1/8" in tact.
3) Use the stop on your drill press to lock this lowest position and ensure the proper depth is cut on the remaining mortices.
4) At this point, if you prefer, you can drill all the way through the top side of the seat for an exposed joint. This provides an even longer, stronger connection and an opportunity to highlight the details of construction with a wedge hammered in from the top, but this time I'm keeping the joint hidden.
Step 8: Rotate and Repeat
Now that you've finished the first mortise you can clear away the wood chips, unclamp the seat from the jig and rotate the seat to drill the next set.
1) Simply align your center mark to the jig, clamp in place, and replace the 1 1/2" bit for the first hole.
2) Then replace the 1" bit and drill through until you hit the stop on the depth gauge.
3) Repeat on the last two.
Step 9: Fit the Legs
Now that all the mortices are drilled you can test fit the tenons. You may need to adjust the length of the 1" tenon if your mortise doesn't cut all the way through.
1) I cut my tenon to 3/8" on the 1" portion but my overall connection is nearly 7/8" including the 1 1/2" diameter portion.
2) Test fit your legs into the seat. You should have a tight fit and nice clean connection as shown.
3) Repeat on the last three legs.
Step 10: Finish
After sanding the parts you can glue together and assemble.
Now that you've made this simple jig you can create mortises at many different angles, try it with both blind and exposed tenons, experiment, and of course, be sure to save it for next time.
Thanks for reading!