Circle Cutting with the Router

There are a number of different methods for cutting a circle, and depending on what diameter is required will often dictate which method is used.

For very large diameters (and we are talking in the order of 1m or larger) the router is a very useful tool.

Get Woodworking in Williamstown (2/ 239 Kororoit Creek Rd Williamstown VIC 3016, ph (03) 9399 1963) have come up with the Rout-A-circle ($27.50), which attaches to the fence of your router to make cutting very large circles easy.

The Rout-A-circle has instructions for attaching to the fence of Hitashi, Makita and Triton routers.  Not being in a position to try it on the other two, I did give the Triton a go, and it was a breeze to attach, and cut the circle.

The largest circle it can manage is approximately 2600mm diameter, which isn’t too shabby. Given how easily it fitted to the Triton fence, you would almost swear it was made with the Triton in mind.

Original Fence

Original Fence

The original Triton fence (which attaches via the quick-release coach bolts) has a circle cutting capability, although it is very limited to about 300mm diameter. Pictured here is the triple-fluted Carb-i-tool spiral router bit which is excellent for this sort of operation.

Preparing for Upgrade

Preparing for Upgrade

One of the times it is very handy having more than one router – also means I have more than one fence, so I am able to upgrade one with the Rout-A-circle, and leave the other in its original configuration.  Not that changing back and forth takes more than a few seconds.

The first step is to remove the non-required componentry. The bolt, washer and butterfly nut are reused to hold the Rout-A-circle in place.

Rout-A-Circle attached

Rout-A-Circle attached

The Rout-A-circle attaches very easily using that existing bolt and nut, and it fits neatly in the slot in the bottom of the router plate.

Upgraded Fence

Upgraded Fence

Maximum Circle Radius

Maximum Circle Radius

Here you can get a better idea of just how large a circle this jig allows. You can’t see it particularly well in this photo, but at the other end of the jig, there is a raised portion.  It is this end that is used when attaching to the Makita or Hitashi routers.

Along the length of the jig, there are holes to take the supplied screw, which is screwed into the workpiece at the radius required.  The Triton fence then allows this radius to be fine tuned if a hole isn’t perfectly located for the job.

First Pass Cut

First Pass Cut

This is the first pass – I took a number of passes mainly because I didn’t bother trimming away the excess material with a jigsaw or similar before starting the routing.  If I was working in a more substantial material, trimming away the excess is definitely recommended.

Circle Cut Completed

Circle Cut Completed

This final shot shows the piece cut away.  The block of wood underneath is there to allow the router bit to fully penetrate without cutting into the table.  Given the table in this case is cast iron, that is rather advisable!

Carb-i-tool Rosette Cutter

Rosettes are not a feature found on most items, or in most rooms these days, but sometimes they are the ideal feature to set a piece apart. In more elaborate pieces, rosettes are hand-carved, but simpler ones can be machined with a rotary cutter.

Carb-i-tool Rosette Cutter

Carb-i-tool Rosette Cutter

This bit is dual fluted, tungsten carbide tipped, but it is not a router bit, despite looking like one. Mount this in a high speed router is asking for serious problems, and likely injury.  Like the wheel cutting bits, these need to be mounted in a drill press.  They operate at a much lower RPM, and have an easily controlled plunge.

Setting up for the milling operation

Setting up for the milling operation

Here you can see the bit mounted, with the table up close and a piece of KD hardwood solidly held down on the table.

Performing the Cut

Performing the Cut

I still operate these bits at a pretty high speed (for a drill press), and control the load on the drill and bit with the rate of the plunge. You are able to easily watch the rosette forming and stop once you see it fully formed.

Continuing the Machining

Continuing the Machining

Drilling the next rosette

Carb-i-tool Rosette Cutter

Carb-i-tool Rosette Cutter

The final product.  This is just one of a number of different profiles available.  You can buy ready-made rosettes, but you are then restricted to only work with the material that they have been made from, and having to incorporate that part into your design, rather than cutting the rosette where you want it, and into the component itself.

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