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Hi,
I am going to make a mess and make a couple of sanding dishes. 15' and 25' the usual sizes.
what I want to do is bang 2 nails on a straight line (24" diameter of the dish size) and flex a piece of dowel in the middle @(12" point ) to get the correct radii.

My question is does anyone know what the measurement I would have to make 90 degrees from the straight line to get the correct curve for 15' and 25'when i flex my piece of dowel to draw the arc?

failing this i could always get the tape measure out and do it that way but i think the first method will make making the rails a little easier.
thanks for any help

Grant,

Go HERE and down load the .xls...to easy.

Cheers

Kim

Yes, I posted this on the MIMF several years ago and I think I did it here about 6-9 months ago but can't find it in the archives. Here is what I posted on the MIMF years ago.

Hope this helps

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Check out this thread for a different method.

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all great methods guys..thanks
Larkim your right that is to easy...i like it

and rod i like the idea of the 30" rails...thats what i am going to do ...this gives enough either side of the 24" dish for the base of the jig to be stable while routing i think...
I used larkims link to the spreadsheet and came up with these figures if anyones interested.

for the 30" rails (measuring up from centre point @ 15" mark to get the point to flex my dowel to get the arc)
15' = 0.62" as close as can get
25' = 0.37"