I hate blind chimneys on model locomotives. For the uninitiated this means a chimney which isn’t hollow, at least at the top. Even very sophisticated kits seem to perpetuate the problem. I know whitemetal doesn’t take big undercuts but it will manage a little bit and since the master will have been made by turning this should be easy enough to provide.
Whatever, the Armstrong chimney looked like it had been filled in with lumpy earth so excavation would be needed.
I carefully measured to find the centre and then tried to drill out with a single reasonably sized drill bit. This isn’t the first time I’ve done this and I know the pitfalls. Start in the wrong place and you’re going to be trying to carve away the leftover infil on one side. Use too large a bit and you go through the sides as the chimney tapers. Too small and there is a fit lip left at the top.
Even the drilling is fraught. In a perfect world a pin vice would be employed for ease of control, but who owns one big enough for the required bit ? Even if you did, working through the lump of metal would be really hard work.
My solution is to use an electric screwdriver with a chuck. The bit rotates slowly so you keep control – or at least stop if you start coming out the side.
I didn’t quite get this right but the repairs with a wipe of low melt solder are easy and the resulting chimney is pretty nice. Most importantly it looks hollow.
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