Posted by Keith Cullum on May 14, 19102 at 08:10:48:
In Reply to: large radius templates posted by andy on May 13, 19102 at 09:40:29:
: How would I create a template, in a piece of 3/4" thick x 8' long mdf, of a curve that is very large i.e. 360" or larger.I want a "perfect" radius, not a line created from connecting a bunch of plotted points.I have a small shop,limited space and few tools.Could I do this with a hand held router?
It's possible...
Space sounds like your main constraint (that is assuming you mean 360" diameter). You will need to make a compass jig for your router that is a little more than 1/2 the diameter of the circle (in this case a whopping 180" or 15'!). Obviously you will need two strips ripped from that MDF attached end-to-end (although may I suggest using a thinner piece of ply for your trammel so you don't have to countersink the base screws as much and the bit will have more travel). Just remove your routers baseplate and use it to lay out the hole locations for the screws and mount your router to the ply..
I suggest laying out the circle on a large (very large!) patch of concrete, gym floor, parking lot etc... using your newly constructed beam compass. Then you can lay your plywood over the markings to get the most radius out of the piece. Attach the stationary point of your router compass jig to 1/2 the outside diameter you want (to the *inside* edge of the bit) and start cutting. A perfect radius every time!
This works for true circles only.
Good luck!
-Keiphus