Workshop Wednesdays - Exploring Swinging and Arching Techniques archive
Wednesday 22 July 2015
Mark Baker and Anthony Bailey explore the swinging or arcing technique when using a router on the lathe
Routers only work effectively and safely under some form of control and guidance. Using either the Paul Howard routing jig or homemade setup as we have done in the earlier articles, it has been executed by sliding or rotation on a baseboard in the horizontal axis. The 'free' method, where the router is slid across the baseboard, uses the shield around the cutter to set the cut depth, while the rotation method uses a depth stop to ensure a constant cut arc that does not need the shield to function.
This time we tried a natty accessory - called a base hinge jig - for the Paul Howard router jig device, which simply bolts to the underside of the router jig base and lets it swing from side to side. The hinge jig comprises four fixing blocks: two to fit to your router jig unit and two to a baseboard, through which runs a metal tube on which everything pivots in a fixed arc. Note: you do need to fix the hinge jig to a board, and as with all the previous articles in the series, an indexing plate/unit is required to lock the work securely in place at specific positions. The board it is fixed on needs to be clamped to the much larger baseboard used in previous issues. We chose a large but unfinished platter that would benefit from some further decoration. After some positional experimentation, we decided that the router had to be offset to one side directly facing the border that required decoration. Being a fairly flat surface, it wasn't hard to work out the projection required to get a slight graduated depth of cut from the edge to the middle.
This is the hinge jig lying over on its side with the router mounted and baseboard fixed into position. It would be perfectly possible to make up an attachment like this. The device is able to slide backwards and forwards within limits, so it can enter the work at any point
This is a view of the setup from the other side with the router positioned to arc across the platter roughly at centre height. Both the baseboard and the device need to be clamped firmly in place on the lathe bed
The testSTEP 3
We did a test 'rub' to gently graze the platter with the cutter tip; this would allow us to check that the cutter path is correct and doable before we go any further
Here you can see the router on its first pass with a 60° engraving cutter. The shield around the cutter is essential as it sets the cut depth when pressing the router against the platter
The cuts start from the rim and go inwards, stopping where the depression in the middle starts. Any loose chippings in the grooves can be wire-brushed out
The first series of arcs can be quite enough in themselves, but we decided to try reversing the effect. The router setup was moved to the other side of the baseboard
To achieve the exact repetition proved to be quite easy, using the indexing plate behind the chuck. The effect is a bit like the Spirograph toy of old and creates a more complex looking effect that can be done quite simply
Just turn the centre and outer edge to ensure the decorative arcs are where you want them to start and finish. Also, remember to clean up the grooves properly