Replies

1. 
   oldhand | Dec 08, 2008 04:09am | #1

   If i get this right you want to cut a perfect circle of plywood and build up the thickness with solid 34 oak under the edge. If that be the case I would use a router with a homemade pivot fixture for the whole operation. A few passes of increasing depth and you have it. If I misunderstood someone will be  along shortly with a better answer probably.

   Retired until my next job.
2. 
   KiddervilleAcres | Dec 08, 2008 04:21am | #2

   tk,

   Am I making my self clear!

   Ummmm, it could be my brain but I don't understand.  You first say it needs to be 1½" thick then ask about a 3" band around the plywood.

   My first thought was to cut two plywood circles then install ½" ribs vis a vis torsion box, but even doing that it would be approaching the weight of full a sheet of plywood. 

   Then you could install a 3" band around the whole thing thus creating an apron.

   Is it me mind?

   Regards,

   Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

   
   

   ---

   Edited 12/7/2008 8:21 pm ET by KiddervilleAcres

3. 
   roqqytop | Dec 08, 2008 04:57am | #3

   C = Pi D = 3.1416 x 46.5625 = 146.28 for your circle.

4. 
   trialnut | Dec 08, 2008 07:56pm | #4

   No need for any fancy math. Just do a full size layout on the backside of your plywood. Draw the 46 9/16 circle and draw a 40 9/16 circle to represent the 3" border. Draw a line from the center to about 4" past the outer circle and another line from center the same length at a 45° angle to the first. Draw a line from the intersection of the inner circle and the first line to the intersection of the second line and the inner circle. Draw another line parallel to this line but a 1/2" or so outside the outer circle.

    Now you have the size and shape that the segments need to be. Just cut 8 of them at 1" thick by the length and width you just determined, (should about 5" wide by 19 5/8" long) fasten them on in an octagon and cut the outside circle. No need to trim the inside of them to a circle unless they are in the way of some other part of the assembly.

   This gives you 8 segments. The same principles are used for any other number of segments. The more segments you use, the narrower each becomes, however, the tradeoff is more cuts and you still lose the offcuts from the angle cuts on the ends.

   Rich

   The Professional Termite

   
1. 
   tkiser | Dec 09, 2008 02:18am | #5

   That's excatly what I was looking for!

   Thanks