Thursday, June 9, 2022

0.2mm from Success

I am never ever ever ever making wheels again. As you can probably guess the next step in the long running saga of building Ivor didn't go entirely as planned.

Having remembered from last time that it was hard work profiling the wheels I set everything up carefully and then turned the first wheel. Just as last time it was a slow process. I'm not sure if that's because the tool isn't as sharp as it might be, or if the brass Shapeways uses isn't ideal for turning, or if the Unimat 3 is a little underpowered for the job, but you have to take very very light cuts and I stopped frequently things cool slightly (otherwise the cutting tool gets so hot the oil smokes). Anway slow and steady got me to a nicely profiled 20mm wheel.

After the success of the first wheel, I made a coffee, and then profiled the second wheel. Then I made another coffee and profiled the third wheel. Then I made another coffee and started on the fourth and final wheel.

I took the final wheel nice and slowly and was just 0.2mm away from a completed wheel (i.e. I needed to advance the cross slide by just 0.1mm) when the threaded rod of the wheel holding tool sheared off and the knurled knob when flying across the room; fortunately away from me. So that's the second time I've had that tool fail now and I've no idea if it's just a bad design or something I'm doing wrong. Either way I was now just 0.2mm shy of four completed wheels which was rather frustrating.
The rod had snapped very close to the wheel so there wasn't enough left to try and screw anything on to the remaining stub. In the end I used the live centre to push the fixing against the wheel. It wasn't pretty and the wheel did slip a couple of times but it stayed straight and allowed me to reduce the diameter by the final 0.2mm.
Fortunately I think none of the remaining work to use the wheels would need the wheel holding tool (they just need holding in the step chucks) so hopefully I can continue on with the build of Ivor, but I don't think I'll ever try making my own wheels again.

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