Ever wondered how to make a perfect oval? Well one day as I was looking through a woodworking catalog I saw
a little gizmo for $19.95 just for that purpose. Being the cheapskate that I am I decided to make one.The prototype worked all-right but by making a few modifications and a few different sized jigs I can now make any sized ovals or circles that I need for use in my woodworking.
Start by cutting a piece of 4/4 stock into a perfect square blank.The one I made is a piece of mahogany cut 5”x5” .On the router table route a 1/4” groove 3/8” deep in the center running in both directions. Flip around and do it again so that both grooves are perfectly centered.
Next set up a dovetailing bit and do the same thing so that the bit widens the original grooves again routing in both directions to center the cuts.
Cut a piece of stock about a 1/4” wider than the widest part of the dovetailed groove. Move the router fence over so that you take out a portion of the stock on both sides to make the cams that will slide in the grooves. Sneak up on making the cams fit by adjusting the fence until the cams slide easily in the grooves.
The next photo shows that I have cut the cams to equal length and drilled a centered pilot hole. I then trimmed the corners of the jig and applied my favorite workshop lube (Pam) to the cams.
The next photo shows the adjustable arm layout. A series of holes drilled 1/2” apart are used to determine the axis which the cams will follow to give the length and width of the oval. The larger holes are used to hold the pencil.
The next photo shows the assembled jig ready to go. I use double sided tape to secure it to the workpiece ,in this case cardboard pattern. This position of the arm gives 1/2 of the length of the oval.
The next photo shows the position of the arm for 1/2 of the width of the oval. By adjusting the position of the screws on the cams you can adjust length and width of the oval.
The next photo shows a perfect oval drawn with the jig.
To draw circles with the jig ,remove one cam and using a longer screw through the other cam to bottom out and lock into the center position of the jig.
Pieces made with shop made oval making jig.
Intarsia of Mabry Mill
Custom marble top coffee table—Brazilian cherry,Peruvian walnut, Bloodwood, Holly.
-- Mike --www.midlothianwoodworks.com