Centering Rings

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For cutting plywood centering rings and bulkheads I use a router and a Jasper Circle Jig (Model 200). This jig was originally designed for making speaker cutouts. It mounts directly to the base of a wide variety of routers. The Model 200 will cut circles in 1/16" increments from 2-1/4" to 18-3/16" in diameter.

The Model 200 is manufactured on a CNC machine to insure that the router mounting holes and the array of pivot hole are located precisely with respect to each other. It is 1/4" thick and seems to be made of something like Lexan.

I purchased mine from my local Woodcraft store for $35.00. They are also available from Parts Express (part number 365-250).

To help reduce the dust spray I also mounted to my router a Shop Vac extension tube with a PVC elbow fitting on the end of it so that it will collect much of the saw dust that is generated.

My Craftsman router (with Shop Vac extension tube added) and Jasper circle cutting jig ready to be mounted onto the router base.

The circle cutting jig is intended to be used with a plunge router. However, I have had excellent results using just my standard router.

Click on this photo to see a larger version of it. A 1/8" diameter steel pin (not shown) can be inserted into one of the calibrated pivot holes. The pin is then put into a 1/8" diameter hole in the plywood piece to be cut. The router then pivots around the steel pin and delivers a precision circular cut.