Thread: Large Sphere from split log of Jacaranda cast

I was asked to turn a split cast sphere out of Jacaranda with translucent yellow/orange resin. Here's the WIP of it being done.

I had a ~300mm Jacaranda log and cut off a length of 350mm. I then used a block splitter and steel wedges whilst calming the base to split the top. I then added timber wedges in the splits to hold the crack apart whilst removing the steel wedges. I then planed down the log to ~250mm dia and siliconed on corflute panel to the base and sides to form the gold for the resin. My pressure pot is 270mm diameter by 400 deep so it was a tight squeeze .

1 split log1.jpg 2 split log2.jpg 3 ready to cast.jpg coloured reson.jpg squeezed into pressure pot for casting.jpg

After a day in the pressure pot to ensure the epoxy resin was set, I took the cast out and bandsawed off the bottom to ensure I had full penetration and the top to remove the wedges and uncast portion of the log. It was then left for a week to ensure the resin was fully cured and hard before mounting between centres on the lathe to turn round and a tenon to mount into my chuck.

4 closed end after cast.jpg 5 open end after cast.jpg 6 mount on lathe.jpg\7 turn round and add tenon.jpg

I checked the colour of the cast with a light then proceeded to turn the blank down to 220mm diameter. I then marked out the sphere at 20mm centres and 10mm centres at the edges with the associated effective diameter for the offset and then parted down to those diameters.

8 mount in chuck with light on crack.jpg 9 turn to dia 220 and mark out diams at 20mm c-c.jpg 10 turn down dia steps.jpg

Next I turned between the levels to rough out the sphere before sanding with a 75mm dia PVC pipe and split sandpaper to form the true sphere. I then remounted the sphere between padded timber cup centres to finish turning and sanding the sphere

11 join up the dia's .jpg 12 sound down round to sphere.jpg 13 slit sandpaper to ensure sanding round.jpg 14 remount sphere between padded cups and finish.jpg

Next I then spray painted the sphere with numerous coats of car clear top-coat lacquer. Being a sphere there was plenty of over spray, so after leaving the lacquer to hard, I wet sanded the surface with Micromesh to 12000 grit before polishing with plastic polish. It came up a treat but made photographing it really hard due to the reflections .

15 sprayed sphere.jpg 17 polished sphere 2.jpg 16 polished sphere 1.jpg 18 polished sphere 3.jpg 19 polished sphere 4.jpg

Although the translucent resin is an orange, because of the refractive index of the resin and shadows, it appears green until a light is applied. I was worried about this, but the client said he originally couldn't decide between green and orange resin, so this way he said he gets both . Pretty happy with the way it turned out .

20 torch lit 1.jpg 21 torch lit 2.jpg