Routing for Oval Inlay | Popular Woodworking Magazine

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Get a perfect fit using a shop made mask.

Oval and circular inlays are an established method for adding class to a project, like the top of a jewelry box. It’s an interesting challenge to create your own inlay, but it’s much easier to select one from a wide range of ready-made designs (see Sources, page xx).

But how will you create a perfect sized indentation for inlay? There’s really no room for error on a prominent detail like this, and you won’t want to ruin an inlay using an imprecise technique. Here is a method of routing the notch that ensures a good fit.

Prepare the insert

All inserts have a layer of tape on one side, which helps hold the various parts of the design together. The ribbon is always placed on the good side, or top, of the inlay. Draw the center lines for the oval or circle on the ribbon using a combined square.

1. Some inlays have a rectangular border that needs to be removed. Cut the edge using a sharp knife, guided by a line of metal.

Some oval and circular inlays are made with a rectangular or square border, which protects the edges of the design. If your inlay has a border, the first step is to remove it (Photo 1). All parts of the inlay are glued together, including the edge, so the edge must be cut with a very sharp knife. A utility knife works well – start with a fresh edge. Guide the cuts with a line of metal, such as a combined square blade. Avoid cutting the oval edge. Make a series of straight cuts – it’s okay if small pieces of the edge veneer remain.

2. Remove the remaining pieces of the edging material by smoothing the oval on a right angle block. This ensures that the edges of the oval are square.

Create a small station to smooth the edges of the inlay (Photo 2). First, glue a piece of 150-grit sandpaper onto a thick block. Block the block on a piece of plywood (melamine works well, because it’s slippery). Smooth the inlay by turning it with your hands: the goal is to create a perfect oval.

Create the model

3. Create a router model from MDF. Flip the inlay over, with the masking tape facing up (this is the show side) and trace around it.

MDF is ideal for making a shape because it is uniform and easy to sand. It can be of any thickness (I’m using 1/2 ″ material here). Cut the MDF to the same size as the piece of wood you will route for the inlay.

4. Remove most of the waste inside the oval using a Forstner bit in the drill press.

Draw centerlines on the model. The oval will not be perfectly symmetrical, so mark a part of the inlay with an “X” and leave the same mark on the template. Line up the center lines of the oval and pattern and trace around the inlay with a sharp, soft pencil (Photo 3). Enlarge the line with a matte pencil.

5. Sand down to the pencil line using an oscillating mandrel sander or sanding drum in the drill press.

Remove most of the waste by drilling (Photo 4). Keep the tip at least 1/32 inch from the pencil line. Use a Forstner bit so you can overlap the holes.

6. Check your progress by placing the oval in the template window. Aim for a snug fit, with no gaps.

Now for the demanding part. Sand to the line, but do not remove it (Photo 5). Take it easy and check your progress frequently (Photo 6). If you sand too much, it’s probably best to start over with a new model.

Rout the recess

7. Attach a thick piece to the underside of the template. The thickness of this piece is determined by the length of the cutter’s cutting flutes.

You will route the recess for the insert with a top bearing flush tip. The template will likely need to be shimmed to lift it high enough above the workpiece so that the tip can create a shallow indentation. I chose a bit with 9/16 “long flutes and made a shim from a 1/4” hardboard (Photo 7), but many combinations of bits and thicknesses will work. Make the thick workpiece the same size as the template, to facilitate alignment when attaching the template to the workpiece.

If your router has a small diameter base, you may need to replace the sub-base with a larger store-made sub-base to prevent the router from tipping over into the template and to allow it to reach the center of the recess.

8. Adjust the height of a top bearing wire cutter. Use scraps, plus a couple of playing cards, to represent the thickness of the shape, thickness, and inlay.

Install the tip in your router. I flip the router over to help adjust the tip height (Photo 8). Place a cut from the template and the thickness next to the tip to represent their combined thickness. Add two playing cards on top – the combined thickness is just a hair thinner than the inlay.

9. Attach the template to the workpiece and mill a recess for the insert. Using this bit, the notch will be exactly the same size as the model window.

Use a scrap piece of wood to test the cutter’s depth of cut. Lock the template in all four corners to ensure the notch has an even depth. Route a test recess. The inlay (not including the ribbon) should be proud of the indentation the thickness of a sheet of paper. Adjust the tip if necessary, then mark the workpiece with an “X” (corresponding to the “X” on the template) and mill the actual recess (Photo 9).

Glue the inlay

10. Check the fit of the insert in the recess. If the measurement is too tight in some places, smooth the edges of the inlay using the right angle sanding block.

Align the two “X” marks and check the fit of the insert in the recess (Photo 10). If the insert is too tight, remove some from the edges using the sanding station. Again, relax – the goal is for the insert to drop into the cavity with minimal pressure.

Make a clamping block about 1/32 inch smaller around the inlay. Apply a thin layer of yellow glue in the recess –but not on the inlay–And place the insert in the notch, with the tape side facing up. Make sure the insert is correctly positioned all around, then place the lock on the inlay and clamp (Photo 11). Remove any residue and let the glue dry overnight.

11. Glue the insert. Apply even pressure using a thick block slightly smaller than the inlay.

Remove the tape by slightly moistening it with water (Photo 12). Sand the inlay flush with fine paper (Photo 13).

12. Remove the tape by wetting it with a sponge. Wait a minute or two, then scrape off the tape using a blunt putty knife.

13. Glue the insert. Apply even pressure using a thick block slightly smaller than the inlay.
Remove the tape by wetting it with a sponge. Wait a minute or two, then scrape off the tape using a blunt putty knife.
Sand the inlay flush with the surrounding wood. Use 220 grit paper wrapped around a cork-backed block.

Sources

Constantine’s Wood Center Oval Sunburst Design inlaid

Freud Top Bearing Flush Cutter, # 50-107


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