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I fancied making an oval house name plaque, and having seen the various ellipse jigs available and their prices, decided to have a go at making my own. It uses the same acrylic circle jig I made in another post, the only difference being that there are two axis to contend with instead of one. To facilitate this, it was necessary to make a small, cross shaped jig with a couple of sliders and two new knobs for the circle jig. Quite a few commercial and home made jigs have a series of holes along the central axis, which limits the dimensions of the ellipse to the spacings of the holes. Mine uses the slot on the circle jig, so that the dimensions are infinitely variable within the limits of the cross base. The actual jig is 150mm across and the smallest ellipse it will cut is 230mm x 170mm, the largest 700mm x 640mm. The smallest dimension is governed by the physical size of the cross jig, the largest by the length of the slot in the acrylic circle base. If I wanted to make smaller ellipses, I would have to reduce the size of the cross jig.

This was all made out of scraps and bits I had lying around...the T tracks were offcuts from the tracks I made for my router table.

The tracks are 19mm across, so the first job was to route two 19mm slots at 90o to each other. (I didn't eventually use the bit in the pic below, as eagle eyed readers will spot the wobble at the end of the RH track.)
Router ellipse jig.

The four 75mm pieces of ally track were cut to 45o points on the mitre saw, and glued into the slots with CA adhesive. This has to be really accurate, or the sliders won't cross over properly. The corners of the jig were then cut off at 45o to prevent the router bit cutting across them on the smallest setting. Centre marks were made to align the jig on the cross axies when setting out.
Router ellipse jig.

Router ellipse jig.

The two sliders were made of 3mm aluminium sheet, cut to size, drilled and tapped to take a couple of 4mm set screws. The sliders must be long enough to span the crossover at the centre of the tracks.
Router ellipse jig.

Roger's Miscellaneous Album.

The knobs and bolts for the circle jig slot were made from two 8mm T slot bolts, drilled on the underside of the T with a 4.5mm hole, to receive the slider studs. (The T bolts are supplied 100mm long and you simply cut them to the length you require.)
Router ellipse jig.

They fit over the slider studs like this to allow everything to revolve once the knobs are locked in place.
Router ellipse jig.

And this is how they sit in the circle jig slot.
Router ellipse jig.

Router ellipse jig.

This is how the whole lot fits together (minus the router).
Router ellipse jig.

Because the router base is now raised by the depth of the 12mm MDF cross jig, I had to cut a corresponding support block to stop the router tipping.
Router ellipse jig.

Here's the try out. The two axies are marked out and the required dimensions marked on them. In this case I am making an ellipse 300mm x 200mm, so my marks are at 150mm x 100mm from the centre. The jig is aligned and screwed down ( you can use double sided carpet tape if you don't want holes in the surface).
Router ellipse jig.

The long axis is set by the rear knob...the slider must be across the join...and the router slid along until the cutter edge aligns on the mark. The knob is locked off.
Router ellipse jig.

The router is then moved 90o so that the front slider is across the joint, and the router slid so that the cutter aligns with the short mark. Lock the knob.
Router ellipse jig.

All is ready to start routing. I was using a piece of 18mm MDF for the first attempt, but would normally be a piece of nice hardwood. Take it easy, in about 3 or 4 passes of increasing depth. First pass.
Router ellipse jig.

The ellipse finally cut out.
Router ellipse jig.

To finish it, I used a bearing guided ogee cutter to make a decorative moulding round the edge.
Router ellipse jig.

Router ellipse jig.

 

 

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