Practical Technologies Base Plate Circle Jig Review

Description
The Practical Technologies Base Plate Circle Jig is one of several circle jigs on the market. This device consists of a 0.32" thick machined aluminum plate that replaces the existing router sub base, a dovetailed bar which is attached to the base, and an edge guide fence which attaches to the bar as required.

The base plate comes un-drilled or pre-drilled for a specific router, this is not one of those base plates that looks like Swiss cheese, only the holes that are required are placed in the plate. The 1 3/16" opening in the base plate will also accommodate PC style guide bushings. An Allen wrench is also included.

In Use
Installation is simple, remove the original base plate and replace it with the Base Plate Circle Jig. I would suggest using a centering cone to ensure any guide bushings used are centered on the bit.

For normal router operations, the dovetailed bar would be removed. This leaves an open slot in the base but aside from this and the care it will impose upon the operator, there is no difference to the router except that its plate will probably be about 1/8" thicker than the OEM base plate and probably flatter.

To use the plate as a circle cutting jig, the dovetail bar is slid into its groove to the appropriate position and the set screws are tightened down. The instructions caution against over-tightening these screws and it really only takes a light amount of pressure to hold the bar in place. Because I tend to look for these things, I noted that the set screws are quality dome shaped types to prevent marring the base when tightened, a nice (and important) touch. I did notice that when tightened, the bar will push past the plane of the base by a few thousandths of an inch, I don't think it is an issue though.

At one end of the bar is a small 1/8" diameter pin the operator would place in a pre-drilled hole. The distance from the center of this hole to the inside or outside edge of the router bit determines the radius of the circle. The jig is capable of cutting circles from 2" to 18 3/4" in diameter measured at the center of the bit. There is no scale or anything built into the jig so the cutting radius must be measured. All of this is fairly straightforward, not unlike many other circle jigs or one you may make yourself.

Should one require an edge guide, the one supplied can be installed onto the dovetailed bar (over the fixed pin). It is attached to the bar with a single screw and even though the attachment point is small, it is quite strong. The guide length is small at 7" but should be adequate for many routing tasks. The 5/8" diameter bit opening in the guide is also small.

Summary
The only thing I wish I could do with the jig is turn the bar over and slide it in the base with the pin up out of the way. This would keep it handy and fill the slot on the base. As is, the Base Plate Circle Jig is a nice, compact router attachment. It replaces the original base plate with something that is probably better that what it came with and adds the edge guide and circle cutting capability at the same time.