Thread: Circle cutting

G’day all,

Need some advice on routing a circular table top.

What I’ve got so far…

I glued up 5 lengths of Vic ash – 90 x 19, sanded both faces smooth, then drew and cut a rough circle close to 420mm in diameter with a bandsaw. On my router table I installed a new, sharp, straight bit. I made a circle template using a length of wood that fits my t-track – it has a small nail sticking up that fits into a hole drilled into the centre of the underneath face of the prospective table top. The template can slide along the t-track so I can adjust the distance to the router bit, then can be clamped in place.

So I have the table top in place positioned so that when I spin it the smallest part would touch the router bit making about a 2mm cut. The plan was to cut this circle first, with the bit fully raised, then move the guide a little closer, maybe another 2mm, make that cut, etc, until the edge was a prefect circle.

Big mistake. Worked fine until the table top spun so that the long edge of one of the side lengths got to the router bit. It ripped a large splinter out of the wood. Very large.

Ok. Start again. This time I lowered the router bit below the surface, positioned the table top at the final position (now giving me a 400mm diameter to clear the ripped-out bit), started the router, then raised it slowly so it took a small cut (again about 2mm) from the bottom of the wood. I continued to make a full circle cut, raising the router 2mm each time. When I finished and looked at the table top edge I found a lot of chunks ripped out, especially where the router bit was cutting against the grain.

Third try. I moved the guide a little closer, so I could cut around 3mm more to smooth the edge (now a 392mm table top – sigh). This time I used the cut-and-raise-the-bit method, but I first back-routed the 2 edges of the table top where the router bit was catching and pulling splinters. Worked better than the other methods, but as I had to go back and forwards over the same quarter-circle part of the top about 9 or 10 times to finish the back-routing I ended up with ugly burn marks that left a noticeable dimple in the edge when I sanded them out.

Can anyone suggest a better method?

Cheers,
Adam