Replies

1. 
   saschafer | Mar 05, 2008 07:23pm | #1

   Are you asking about the laying out of the oval, or the cutting itself?

   Laying out: If you want a true ellipse, there are any number of techniques for laying them out, including the string-plus-two-nails method. If you want something more like a racetrack (straight sides with circular ends), then a large compass or a piece of wood and a pair of trammel points will do the trick.

   Cutting: I would rough out with a jigsaw. If I wanted a nice clean edge, I might cut a template out of 1/4" MDF, fine tune it with sandpaper, and then use it with an edge-trimming router bit to cut the actual piece.

   -Steve

    

1. 
   MikeBinYEG | Mar 05, 2008 08:53pm | #2

   Thanks

   All good ideas to consider. 

2. 
   Steinmetz | Mar 05, 2008 09:24pm | #3

   You might search the knots archives for cutting ovals .
   In the past, several posters 'chimed' in( including me)on the subject
   T
   here's a product available to attach to a hand held router (not unlike a trammel) but will, when adjusted, guide the router to cut perfect ovals.
   I made one myself many years ago. The device incorporates two sliding dovetailed runners inserted into to a + shaped pair of matching dovetails. When you rotate the trammel, the dovetails do not describe a circle,but magically describes an oval. If you use a moulding cutter ,and a plunge router, you can make inside AND outside ovals (Picture frames etc.)
   Google up: Highland Hardware Infinite Oval and buy or make your own. Steinmetz

   Edited 3/5/2008 1:45 pm ET by Steinmetz

2. 
   [email protected] | Mar 06, 2008 04:41am | #4

   An oval or an elipse?

1. 
   MikeBinYEG | Mar 06, 2008 04:46am | #5

   An oval.
   What I am looking to to is make a oval table top out of 3/4 ply.

1. 
   [email protected] | Mar 06, 2008 05:09am | #6

   For an oval, (two half circles with parallel straight sides in between): 

   I would cut to width and length, then use a router on a trammel anchored by nails in the bottom surface and cut the two half circles, using a compression spiral bit to avoid tear out and chipping.   

1. 
   harrycu | Mar 06, 2008 08:44pm | #9

   Quote:  "For an oval, (two half circles with parallel straight sides in between)"

    

   I'm sure I may be missing something here, but wouldn't two half circles make a circle and not an oval?

   Just my two senses.

   Harry

    Following the path of least resistance makes rivers and men crooked.

1. 
   saschafer | Mar 06, 2008 09:35pm | #10

   You're missing the "parallel straight sides in between" part:

   View Image

   -Steve

    

   
2. 
   harrycu | Mar 06, 2008 09:52pm | #11

   Okay, and that is technically a sort of oval, but not an elipse.

   Thanks,Harry

    Following the path of least resistance makes rivers and men crooked.

3. 
   [email protected] | Mar 06, 2008 11:05pm | #12

   The working definition they gave us in drafting class a bazillion years ago, was:

   Ovals are two half circles, joined onto a rectangle, and an ellipse is a circle viewed from anywhere beside directly over the paper. 

   Now from the math stand point an oval is any curvilinear, differentiable, closed planar form, with at least one axis of symmetry.  Maybe, the definition isn't really locked down very well. 

   I asked for clarification from the op, because he was getting advice on how to do an ellipse, and I wasn't sure of what he wanted.  I guessed that what he wanted was the "oval" I was taught in shop class, as opposed to an ellipse. 

4. 
   saschafer | Mar 06, 2008 11:11pm | #13

   "Now from the math stand point an oval is any curvilinear, differentiable, closed planar form, with at least one axis of symmetry."

   Hmmm. I think you need to add "convex" to that list of adjectives:

   View Image

   -Steve

    

   
5. 
   harrycu | Mar 06, 2008 11:14pm | #14

   I stand corrected. ;^]

   Harry

    Following the path of least resistance makes rivers and men crooked.

3. 
   Jfrostjr | Mar 06, 2008 04:16pm | #7

   I have just finished such a project. It is now out being fitted for a glass top. I will post photos after I pick it up on Friday.

   I purchased a MicroFence ( http://www.microfence.com/pages/Ellipse%20Jig.html) ellipse attachment (Oval = Ellipse, same thing), glued-up 8/4 cherry and used a plunge router to cut 2 ODs and 2 IDs. Outer dimensions were about 44" x 24".

   Frosty

   "I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922

   
   

   ---

   Edited 3/6/2008 8:34 am ET by Jfrostjr

4. 
   Boogalee | Mar 06, 2008 05:53pm | #8

   Check this out.  It shows how to create an ellipse.

   http://link.brightcove.com/services/link/bcpid979295690/bclid1338929762/bctid978961083

5. 
   TimNott | Mar 07, 2008 06:51pm | #15

   Last time I used a router to cut an oval I made a perspex trammel bar to hold the router with two pivots stuck in it.
   The pivots ride in slots that align with the centre lines of the ellipse.
   This was for an oval window - the pins are very close together as the ellipse was not far off a circle. As far as I can remember, router bit to nearer pin = 1/2 shorter dimension of ellipse, router bit to further pin = 1/2 longer dimension of ellipse.

   
6. 
   mahogany | Mar 07, 2008 10:07pm | #16

   I use a shopmade router jig to cut ovals. It works good, with some limitations settings the axis. I can put some pics if it helps you.