Ellipse

NOTE: As platform rotates, dovetail blocks slide in channels, always staying perpendicular to each other.

Rotate Chop Saw

STEP 4: Rotate platform to draw or rout ellipse.

NOTE: As platform rotates, dovetail blocks slide in channels, always staying perpendicular to each other.

assembled jig between bench dogs, or screw it to the workbench, making sure the suitcase latch remains accessible.

To draw an ellipse, first determine the lengths of the major and minor axes of the ellipse, and set die slide for the difference between these lengtlis. (See Fig. 3.) To avoid undue strain on the dovetail blocks, always center the long axis of the platform on the slide har before making adjustments. Then simply loosen the lockstrip, pull the slide bar out to the desired difference setting on the scale and reclamp the lockstrip.

Tape your paper to the platform with masking tape and draw faint pcipcndic-ular centerlines on the paper coincident widi the lines of the platform. The intersection of the lines will always be the exact center of your ellipse.

Set your pencil on the long center-line of the desired ellipse as shown in Fig. 3. You don't wrant too much pressure on the pencil point, so adjust the height of the holder with additional spacers or loosen the wedge and retract the pencil as needed. Now draw the ellipse by rotating the platform.

To make other ellipses the same shape but of different sizes, simply reset the pencil (or router) location without changing the slide setting. To change the shape of an ellipse, adjust the slide and reset the pencil (or router) according to the size you want.

Routing an ellipse is only slightly more involved. Instead of your pencil block, attach a plunge router to the guide bars.

Center your workpiece on the platform and attach it with screws, double-stick tape or hot-melt glue. After lining up the major axis with the slide bar as above, mark the long end of the ellipse and line up your router bit on the waste side of your mark.

Be sure you clamp the plywood arm of the router fixture firmly to the bench. Then start the router, plunge the bit about 'A in. into the work, and rotate the platform slowly and evenly in a clockwise direction. (See photo, page 31.) It's a good idea to cut a little outside your line and follow up with a final trim pass oncc you've plunged all the way through.

For cutting out ellipses, a sharp i^-in. or '/¿-in. carbide-tipped straight bit will work fine. If you'd like to chamfer or round over the edge of your ellipse, use a hand held router and a ball-bear-ing-pilot bit after you've cut out the elliptical shape.

Troubleshooting the jig is straightforward. If you find that a pencil line or router groove doesn't pass through the starting point after one revolution of the platform, chances arc that something has slipped slightly. Check to sec that the jig's base is screwed down properly, that the pencil/router fixture is securely clamped, and that the adjustment slide bar hasn't moved.

If your ellipses appear slightly skewed, cither your channels aren't centered properly on the platform centerlines or you didn't liave the platform centerline directly over the center of the slide bar when you set the pencil or router on the major axis.

Finally, any wobble in the dovetail blocks could translate into a slight wandering of the pencil or router. Try tightening your attachment screws slightly to take out the slop.

If you need to cut ellipses with a larger axis difference than the 48 in. possible here, you can add extension channels or make a larger jig. A

Was this article helpful?

0 0
Woodworking Tools and Installation Tips

Woodworking Tools and Installation Tips

There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.

Get My Free Ebook


Responses

  • christine
    How to cut an ellipse in wood?
    9 years ago
  • Doda
    How to draw a ellipse with a stick jig?
    8 years ago

Post a comment