It seems I am getting lax at downloading the pictures from the new Nokia N8 to update the blog, so here is a quick summary of the progress being made.
I have a couple of pictures here of boring the highpressure cylinder and pistonvalve chest – the problem with these two is that they are too small and long to allow me to get the boaring head in – and I have an inbuilt hatred of between centre booring bars – so thy had to be bored with a long boring tool… (here’s a video) This is right at the start of the boring process, and the cored hole in the casting is somewhat off centre, so at this point it all looks a bit wobbly and we have an interuppted cut in progress.
This approach to machining has resulted in the bores being a bit tapered (wear in the 60-year-old harrison’s bed 😦 ). It looks like they might be about 2thou off parallel, so I will need to pay some attention to this. For the piston valve I can probably make the liner match – for the cylinder perhaps some AGRESSIVE honing might help… we’ll see.