AW Extra 1/10/13 – Make Crown Molding on the Tablesaw

Make Crown Molding on the Tablesaw

By Tim Johnson

Finding factory-made crown molding to match your cherry or walnut dream project isn’t so easy. Most lumberyards only stock crown molding in pine and oak. Ordering by mail is slow and expensive, especially if you only need a few feet of molding. And there’s a good chance the molding you receive won’t match the color or the grain of the wood in your project.

The solution to these problems is simple: Make your own crown molding. Then you’ll be able to say, “I built this project by myself,” without thinking, “Well, almost.”

I’ll show you how to make classic crown molding on a tablesaw, using a general-purpose blade to shape the profile. Finishing requires a scraper, a block plane, a length of PVC pipe, sandpaper and elbow grease.

You can create almost any molding profile using this method. The molding shown here crowns the “Grand Bookcase”.

 

A simple procedure

To make the molding, you simply draw its profile on the ends of a blank and then cut away the waste, using the drawn-on profile to set the fence and blade height for each cut. Ideally, the cuts barely score the profile line. Planing, scraping and sanding finish the job. Cuts made too deep would require additional sanding that slightly changes the profile.

Create curved shapes by passing the blank over the blade at an angle or by adjusting the blade’s height between adjacent passes. Create flat surfaces by tilting the blade. Some cuts require turning the molding end for end or feeding it on its edge.

My saw has a left-tilting blade. If your blade tilts to the right, work from the opposite side of the rip fence and reverse the orientation of the blanks.

 

Transfer the profile

Make a full-size pattern of the molding (Fig. A, below) by reducing it to 78 percent on a photocopier. (Adjust the percentage, if needed, to match the pattern to your blank’s length and width.)Use this pattern to draw the molding’s profile onto both ends of all of your molding blanks, including a couple extra blanks for test-cutting. Your blanks must all be the same width and thickness. Lengths can vary.

1. Start by cutting coves
that match the concave curves. These cuts require a fence clamped at an
angle and several passes, with the blade raising 1/16 in. each time.
Cut the cove at the bottom of the molding with the blade set at 1/4 in.
and the fence at 18 degrees. Cut the large cove at the top of the
molding with the blade at 9/32 in. and the fence at 24 degrees.

Guides, which have been cut to the correct angles on a miter saw,
make it easy to position the fence. Raise the blade, lay the guide
against the blade’s side and lay the fence against the guide.

The fence must be angled correctly to set it at the proper distance
from the blade. Raise the blade to the correct height and then align two
points: On the molding blank, the fence-side starting point of the
cove’s profile, and on the throat plate, the point where the outside
edge of the blade’s leading tooth enters.

This setup requires trial and error to achieve. Slide the molding
blank forward along the angled fence until it meets the blade. Adjust
the fence—while keeping it at the correct angle—until the two points
align. Clamp the fence to the saw table and lower the blade to 1/16 in.
for the first pass.

Click any image to view a larger version.

 

2. Cut the fillet using your rip fence. The fillet angles 52 degrees,
so the blade won’t tilt far enough to make the cut in line with the
face. Instead, angle the blade so the teeth meet the face at 90 degrees.
You’ll have to make more than one pass. Start at the lowest point.
Reset the fence and raise the blade for subsequent cuts.

 

3. Clean the fillet with a card scraper, using the V-shaped groove as a
guide. A card scraper is great for this job. It’s faster than sanding
and less likely to ruin crisp details. Card scrapers are inexpensive and
easy to use.

 

4. Make a series of stepped, angled cuts to refine the shape of the
compound curve. Tilt the blade to meet the profile and work from left to
right, adjusting the fence and raising the blade slightly with each
pass. It’s better to raise the blade between passes than lower it, so
you’ll be less likely to make a cut that’s too deep.

 

5. Turn the molding end for end and continue making angled cuts to form
the outside of the curve. Cutting from this direction keeps the teeth
perpendicular to the profile. Work from left to right, so you can raise
the blade between passes. Leave a ridge in the middle to provide support
during the following steps.

 

6. Install a tall fence to cut the spring angle bevel on the back of
the molding. The spring angle is the angle formed between the cabinet
and the crown molding—38 degrees and 45 degrees are the two standard
angles. This molding springs 38 degrees; the "Grand Bookcase" molding springs 45 degrees. Use the same procedure for both angles: Stand the molding on edge to make the cut.

 

7. Cut the molding’s top fillet at the same angle, so it matches the
spring angle bevel. Then the fillet will be vertical when the molding is
installed. Just flip the molding, adjust the fence and go.

 

8. Cut the top edge with the molding flat on the saw. Rotating the
molding 90 degrees from the last step allows cutting a square corner
without changing the blade angle.

 

9. Cut the bottom edge square by moving the fence to the other side of
the blade. Leave the blade at the same angle and keep the molding in the
same position. Attach a spacer board to the fence, so the blade guard
doesn’t interfere when you make the cut.

 

10. Remove the support ridge and shape the top of the convex curve
using a block plane. Plane down the slight flare on the bottom cove,
too.

 

11. Smooth the concave curves with coarse sandpaper wrapped around PVC
pipe, a mailing tube or a dowel that closely matches the contour.

 

Fig. A: Crown Molding Profile

This story originally appeared in American Woodworker November 2005, issue #118.



November 2005, issue #118


Purchase this back issue.