The Twelve Piece Burr
A good nickname for this puzzle is
"The Intimidator," because all twelve
pieces are identical, and taking the puzzle
apart is as confounding as putting it
Make the pieces
1. Cut 4-1/2" long blocks from square 3/4"
stock, including extras for test cuts (Fig D,
2. Make a pair of 3/4" x 3/4" x 7/8" spacers.
3. Set up the saw and the jig to cut 3/8" by
4. Clamp the jig's right stop block 1-7/8" from
the edge of the 3/4" slot.
5. Snug a 3/4" spacer against the right stop,
followed by a test piece and the other 3/4"
spacer. Butt and clamp the left stop block
against the spacer.
6. Cut dadoes in a couple test pieces. Fit them
together to check the dadoes’ width and
depth, and make necessary adjustments.
7. Cut this dado in all twelve pieces.
8. Flip the piece end for end and reinstall it
between the two spacers. Cut a second dado
in all twelve pieces. Both dadoes should be in
the same face.
9. Rotate the piece one-quarter turn toward
the dado set and reinstall it with both 3/4"
spacers on the left. Cut this dado in all twelve
pieces. This last cut creates a tab, which can be
used to help assemble the puzzle.
Assemble the puzzle
1. Assemble four pieces to form a tic-tac-toe
grid. Orient two vertical pieces with their tabs
on the right and facing to the front. Then
install the two horizontal pieces with their tabs
on the inside and facing to the back. A rectangular
space should appear in the center.
2. Install the next two pieces with their tabs on
the left and facing up. Slide in one piece from
the left side, until it locks around the vertical
piece. Slide the second piece halfway through
the rectangular space from the front. Then
move it to the right, to lock around the other
3. Install the next two pieces with their tabs on
the inside and facing down. Slide them down
from above and lock them in place. You now
have two intersecting tic-tac-toe grids.
4. Slide the horizontal tic-tac-toe grid to the left.
5. Install the last four pieces. Orient the two vertical
pieces with their tabs on the outside and
facing to the right. Slide in one from the front
and one from the back. Lock them in place.
Orient the two horizontal pieces with their tabs
on the outside and facing to the left. Install one
of these pieces from the top, and one from the
bottom. You may have to hold onto the bottom
piece during the next step.
6. Complete the puzzle by sliding the horizontal
and vertical assemblies together.
(Note: Product availability and costs are subject to change since original publication date.)
Woodcraft, woodcraft.com, 800-225-1153,
Toggle Clamp, #143938.
This story originally appeared in American Woodworker June/July 2009, issue #142.
June/July 2009, issue #142
Purchase this back issue.