ON TEST: Arbortech Spheroplane

Clockwise from above: The new Spheroplane is a unique powercarving attachment that will form convex and concave curves and even shape complete spheres. The cutter arrangement viewed from below. An included sanding attachment comes with a range of grits.

Review and photos: Raf Nathan

Arbortech’s innovative new Spheroplane features an adjustable carving radius made with a flat spinning steel disc that holds two round tungsten cutters. The cutters rotate to expose a new sharp edge if needed.

The cutterhead sits in a steel shaft and is shrouded with a tough rounded plastic collar that raises or lowers on the threaded shaft. Extending the cutters slightly beyond the base forms a concave arc, while retracting the cutters gives a convex arc. With the round base sitting on the wood the tool only wants to create a sphere, or in the case of a bowl, an arc of a circle.

Fit and feel

Fitting the tool to a standard 115mm or 125mm angle grinder is pretty straightforward. Thread and tighten the cutter onto the shaft and use the bent bar to click and lock it to the grinder. This bar tends to float around so I taped it to the angle grinder.

Everything is very well made. The cutterhead is nicely machined and Arbortech state the collar and base are made from engineered plastic. Moulded into the collar is a dust extraction port that works very well hooked to an extractor. Whilst there were plenty of shavings on the floor, my dust extractor grabbed at least 80% of produced shavings.

As this is a new tool there is not much learning material online.* The inventor, Kevin Inkster, and his colleague Seth have provided good videos on using it, but the learning comes from practice.

Screwing the blank to a block of wood and then a board allowed me to hold it securely.

First use

You can make spheres but I began by making a platter 300mm diameter from wood 35mm thick. Basically it’s all about seating the base on the wood so the tool keeps forming an arc. The initial cuts are always coarse but as you progress, the base of the tool will eventually sit neatly on a cut surface that’s quite smooth and clean.

Carving the inside first is easier. I found carving the outside much more difficult partly because holding the wood securely is an issue. You can sit the bowl on a bench with a couple of stop blocks but I wasn’t happy with this. My first platter creation was acceptable with the finish off the tool quite good.

Working through a series of reference marks to begin on the outside of a bowl.

Second time around

For my next piece I used a large Huon pine slab that was 75mm thick and bandsawn to a 500mm round blank. Usually, you would carve a bowl of this size with chisels or turn it outboard on a big lathe. Woodturning on this scale is advanced work, so being able to tackle this with a power tool is quite an opportunity. I chose to carve the outside first and leave the easy part till last.

Holding the piece

I coach-screwed a 50mm block to elevate the wood and give plenty of access to the Spheroplane. To this I screwed a 150 x 19mm hardwood board and clamped this to two stands. This meant I could walk around the piece to make continual cuts knowing the wood was safely clamped.

It begins

Use a marker to draw reference circles on both sides so you can check your progress. It took at least two hours (including breaks) to mostly finish the outside, but expect to work faster when you have learnt to use the tool. I struggled a bit to get a perfectly clean ‘off the tool’ finish, and this was partly because I wasn’t happy with the arc and changed the cutter extension and removed a little less towards the base. So I now had two arcs.

Ideally you don’t change the arc so you can keep refining the cut. Remember the tool only wants to form an arc of a circle – you can’t create your own curve. A bowl needs a flat or concave base to be stable and not rock around. I used the tool to quickly cut a concave for a dished base.

Continuous cuts will achieve a progressively smooth surface.

Completing the outside

After achieving an acceptable finish I switched to sanding mode to smooth and even the surface off. Remove the cutterhead and replace it with the velcro-faced 50mm sanding pad. This quickly spins on to the shaft and comes with 40, 80, 120 and 240 grit discs.

Choose your grit and with the tool switched off lower the sanding head till it just touches the wood, then lock the depth. The sanding function works very well, and you can take it quite quickly up to a fine clean finish – a light touch is all that’s needed. The dust extraction for sanding is excellent.

The offcuts of the original blank were used to make a holding jig for carving the inside.

Tackling the inside

To carve the inside I nested the bowl on some padding within the original corner offcuts. This worked quite well although you need to resist the tendency to grab the wood with one hand when the blank moves, as it will. If your hands are always on the tool, you are relatively safe. It is a powerful carving tool and deserves respect.

The internal carving is easier and more controllable. There were still a few hours’ worth of cutting to remove the bulk of the waste and complete the bowl. The more you cut, the smoother the surface will become however the walls will also become thinner. Importantly, the inside and outside arcs should match as close as possible, avoiding a centre that’s too thick and heavy.

Finishing the inside

After hanging off the end of the angle grinder for a few hours there came a point where I stopped and switched to sanding mode. You can sand from say 80 grit and work your way up to a fine finish. I still needed to hand sand to achieve an even and smooth surface.

A flat rim was marked and then created with a sharp chisel.

I think bowls need a rim otherwise when viewing it there is nowhere for the eye to rest. It makes a difference. Here I chiselled in a slightly convex edge about 15mm wide.

The bowl was given a coat of hardwax oil, buffed immediately, left for a day and then sanded to 400 grit before polishing again, and again.

The completed bowl in Huon pine made with the Spheroplane.

Next time!

In future I will remove as much waste as possible prior to powercarving. Outer edges can be planed or chainsawn off while a large bit on the drill press can remove waste inside the bowl.

The new tool

The tool is very well made although I wondered about the engineered plastic used for the collar. Over the making of a large bowl, the collar could  travel 100–200 metres or so and must eventually wear a little flat area on the base. This could affect how it sits on a wood surface – however replacement collars are available for $39.

My angle grinder is a low cost hardware job. A cordless tool with a short body and variable speed would be a better choice. Variable speed would give a low setting for sanding.

I used some hard Huon pine however the Spheroplane can tackle Australian hardwoods just as well. Its carbide cutters give good results even in difficult woods. To be able to create accurate large bowls (or spheres) with a power tool is a feat, let alone the ability to handle virtually unlimited sized wood slabs of any species. This is a revolutionary and quite brilliant tool and used safely it’s very powerful. I am already planning my next work – maybe an even larger bowl.

* At time of review and writing this was the case, however there are now many tutorials available online for using the Spheroplane.

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Raf Nathan @treeman777 is a Brisbane based woodworker and AWR contributor.

Review tool supplied by Arbortech, see www.arbortechtools.com/au