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Location: Perth, Western Australia, Australia

I have spent a life time working with wood now retired and still working with wood finding new methods of using the World's most versatile Woodworking tool The Router

Thursday, May 11, 2006

Cutting Crcles withthe router

Investigate the alternative methods of routing Circles

Four of the most commonly used circle cutting jigs which are used regularly by a number of outer enthusiasts.

(1) Trammel Method
Some router manufacturers produce a trammel as an accessory. The Trammel consists of a metal bar that fits through the holes on the side of the router base, with a pin fixed at the other end as a centre point. (This pin can be adjustable as seen in the diagram.)This method of routing circles will restrict the minimum radius to greater than 1/2 the diameter of the router base

(2) Base plate (a)
Remove the router base plate, and attach a 12mm Base plate approximately 300 x 160 and screw it to the router base, using longer screws and washers. The washers and screw heads should be sunk below the surface of the base.

(3) Base Plate (b)
Remove the router base plate. This jig can be constructed from clear hard acrylic or MDF laminated both sides.

(4) Alternative trammel design
Simple trammel design constructed from 12mm plywood or MDF with a series of holes for a variety of radii.

Consider the advantages and disadvantages of each jig before proceeding to construct your jig. You should also consider the new circle cutting jig.

Advantages Trammels are readily available for purchase and are capable of producing a large number of circle especially with extensions added to the arm. Adjusting to the various radii required is relatively simple on the router base or on the arm of the trammel
Small circles cannot be cut. {Smaller than 160mm diameter} (approx)

Base Plate a
Relatively simple to make by removing the router base plate, and attaching a 12mm Base plate approximately 300 x 160 to the base of the router. and inserting a panel pin to the required radius. The panel pin is filed to a point. Small diameter circles can easily be cut.
To change the radius the pin has to be relocated to another position.
There is no fine adjustment available.

Base Plate b

The jig is adjustable to produce a greater variety of circle.
Additional ‘Tee nuts’ can be added to increase the size of the circle required.
Small diameter circles can be cut easily
New router base plate has to be constructed.
Router base plate has to be removed.
Any variation to circle diameter, will require the adjustment of the four screws holding the new router base plate.
Special metal pin is required. (Tee nuts are readily available for purchase)

Simple Trammell

Simple to make from strips of boarding.
No special pins are required as the arm can be screwed or pinned to material.
Trammel can be easily fitted to the router base.
Small circles cannot be cut easily
There is no fine adjustment

(5) New Circle Cutting Jig
Side Fence Attachment is used to hold the router. (This will depend on brand of router you are using)
Greater variety of circles can be produced
Side Fence Attachment is added to a piece of MDF 300 x 180 x 12mm (approx). No great expenditure
Any ‘Fine’ adjustment to the radius of the circle is made from the top, by sliding the base of the router on the rods.
Small radius circles can be cut easily

Takes time to construct and requires special pins

Details of the new Circle cutting Jig are available on CD-ROM 2


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