Recently I wrote about a challenge I'd been set to let go of the idea that my wood turnings should be 'things' with purpose, such as bottle stops, lidded boxes, bowls etc etc. And instead simply make something that looks interesting. My first attempt went ok, but it was alwasys just one of 2 ideas I'd had. The second idea was somewhat more ambitous. The main thing I wanted to achieve was to have one colour of wood turning trapped inside a second contrasting color. Initially I had a thought that the shape of the trapped piece should be interesting and multi-faced. So I attempted it by making a 3 sided piece, then taking that and mounting it at 90 degrees, using some specialy cut blocks to hold the uneven sides. I had originally intended to then turn it 3 sided the other way. This really did not go according to plan. It was very dificult to stay accurate and even once turning at 90 degrees to an already odd shape. The resulting lump of wood was uninspiring and not at all what I'd hoped for. Whilst it is a little frustrating to spend time on something only to discard it. I guess that is what experimentation is all about.
My second idea for the trapped piece was considerably more simple. I just took a small length of ebony, and shapped it into a shape a little like a spinning top, a point at one end, and rounded at the other.
Having made this piece I then roughed an oak log down to cylinder. I wasn't initially sure how big I was going to make the outside profile so I left it pretty much as big as I could. With a tenon cut on each end. Then cut it in 2 about 2/3rds the way along. This allowed me to then mount each piece and hollow a recess big enough for the ebony piece to fit inside. At this point I decided that I'd make it relatively tight, such that the ebony piece would be unable to rotate on end inside. Looking back I think maybe it would of been better to cut a bigger recess. More on that later.
As is so commonly the way, at least for me, I spot things that might be a problem just that little bit too late to do much about it. Having left the oak cylinder quite wide, and the recess now relatively small it left me with quite a large surface area that needed to fit perfectly together. I suspect that had I left much less waste wood, it would of been easier to achieve a nice tight join.
I wrapped the ebony piece in kitchen roll and inserted it into the recess ready for being sealed in. At this point I realised that any little inaccuracy of turning the recesses, would mean the interior recess might not line up that well. When I ultimately pierce through to show the ebony trapped inside, there might be a step. Again this might of been easier to gauge with less surface area to join, and possibly if I'd cut straighter edges on the recess I could have done something to help alignment... still too late now so plunging onwards...
Once it was glued and dried, I remounted on the lathe and prepared to shape the exterior profile. My vision was of a cage atop a wineglass like stem. The first thing I did was figure out how thick I really wanted the walls of the cage. I really should of decided this before I started. I decided 5mm might be about right. And I figured out what diameter I needed to rough down to and set to it. This was where I really appreciated how much I'd wasted by using the whole chunk of oak because I hadn't really fixed my sizes before I started. So whilst I was working to a plan in terms of shape, I really should of thought through the sizes too. I know, it's obvious when you put it like that, but again, sometimes it is easier to make these descisions as you see it coming together as a real 3d object.
I shaped and finished the outside profile of my cage. Without starting to turn the stem. I didn't want to weaken the structure and introduce wobble until I was ready. The next thing to do was use my new indexing rig to allow me to mark out even spacing around the edge for cutting through the shell. For it's part the indexing worked well. My newly created fixed point did the job and seemed to allow me to repeatably go to and from specific points accurately. Initially I marked out 6 slightly spiraling windows to cut through. So then I set to work with my rotary tool and a carbide cutter.
This is where things become difficult to control. It is very easy to slip with a rotary tool and gouge accross the surface rather than in the area you're cutting. It's also difficult to be precise with lines. However I cut through the first window without too much trauma.
At this point I realised that my wall thickeness was still way too thick. I'd been slightly worried about going to far so was on the conservative side of 5mm thickness. And it was just way too thick, particularly for the size of window. I Realised that I needed to go thinner on the shell. Before making any more windows.
I also realised the size of window was just too narrow, given the relatively small interior space, compared to the size of the ebony piece. I wanted to let more light in, and be able to see more of what was inside. So I dropped the windows from 6 to 4 and made them nearly twice as wide.
It is very difficult to get nice clean cuts with a rotary tool. It is then very hard to sand the irregular sides of the windows. It also, became apparent that it was hard to control at the point I broke through into the inside. Whilst the ebony piece was wrapped in kitchen roll, it took some damage whilst I was working. This is not good since there is nothing I can now do to repair it. If I were to attempt this again I'd make the interior space at least 50 percent bigger and provide more wadding to protect the trapped piece.
Once I was fairly happy with the cage section I moved on to shaping the stem and base. Sadly at this point disaster struck.... I had a heavy catch at the thinnest point of the stem and it simply snapped. Oh bother. I thought. What a nuicsance.
I decided to finish off the cage section as an egg shape, and perhaps make a separate base for it to sit on. I remounted it the other way round. And rounded off what was supposed to be the bottom into what is now the top. I then realised I did have enough wood left to make an integral stand, just a little smaller than I had intended.
Once again the finished result is as much a factor of how I compensated for mistakes as it is faithful to the original intent. I don't necessarily see this as a bad thing.