Replies

1. 
   WayneL5 | Feb 08, 2004 06:08am | #1

   There are several ways of laying out ellipses.  I can't remember any of them, but the archives have past discussions, or maybe someone can post one again.

   As for the tool to cut with, a jigsaw would not be my first choice.  Depending on the quality of workmanship this project requires, I would layout and cut the ellipse of 1/4" MDF about 1/16" over size all around, then fair the edges with rasps, files, and sandpaper, or on a sanding machine.  Cut the plastic about 1/8" oversize.  Then stick the pattern to the plastic (with the protective film still in place) with double stick tape and use a pattern-following bit in a router table to bring the plastic to final shape.

2. 
   15Broad | Feb 08, 2004 04:11pm | #2

     Start by drawing the length and height lines (axes).  Each line must cross the other lines center at a right angle.  Take a compass and set it to the distance from where the lines intersect to one end of the long axis, take it as half the long 'diameter'.  Now with the compass point at one end of the short axis, mark the long axis with the pencil.

     Turn the work so that the long axis runs horizontally (left to right).  Find the left hand mark you just made with the compass and push a thumbtack or something into it.  Push pins into the right hand mark and also the right hand end of the long axis line.  Tie a string from the left pin, loop it around the pin on the extreme right and tie it to the pin between the two.  Remove the right end pin and use the string as a guide to draw with.

     I hope I translated this clearly enough to understand.  It confused the heck out of me when I first read it, but it should work.  Try it out on paper first unless your grasp of geometry is better than mine.  Good luck!

3. 
   PlaneWood | Feb 08, 2004 07:53pm | #3

   Put two nails in a board, say, 6" apart.  Tie a string around the two nails leaving some slack, say about 1" at one end.  Put a pencil point inside the string and use the pencil to pull the string taut.  Keeping the string taut, trace an elipse onto the board.  Dental floss works well.  Experiment with different distances between the nails and different lengths of string.

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)
   PlaneWood

4. 
   fredsmart48 | Feb 09, 2004 12:18pm | #4

   http://mywebpages.comcast.net/krumy/ellipse/ellipse.html

   http://www.josephfusco.org/Articles/Ellipse/Ellipse.htm

   http://geocities.com/heartland/8108/ellipse.html

   http://www.microfence.com/pages/Ellipse%20Jig.html

   have fun.