Re: Looking for a micro/mini lathe & milling machine

Glenn Butcher

For a long time I've wanted to do brass scratchbuilding.  Recently, I set out to do just that, and came to the conclusion that a $2-3000US investment in machine tools just wasn't practical.  I guess I want to build the model just a little more than I want to learn machining...  :D

I just bought a resin 3D printer, and I'm going to try a "print-if-possible" approach, similar to what Jeff Kraker did for his On3 Shay, described here:  Some things you just can't get away from metal, e.g., drivers.  Nigel mentioned domes, and that's the thing that really got me thinking about printing.  I researched how folk were cutting domes on a lathe, watched a video of a fellow cutting the curved base with a fly cutter on a lathe, then turned to a simple script in OpenSCAD which did the same thing by subtracting a cylinder from the base, easy-peasy.  Well, maybe not so easy if you've never done such, but the tools to do it take up so much less space.  

I know this is going to look complicated, but like most things computer, it's pretty simple once you understand what's going on.  This is a screenshot of my DRG #168 steam dome model, and a piece of the script that defines it.  The highlighted line, #41, is the cylinder that's subtracted from the base with the difference() command at line #33 to make the curved base to fit the boiler:

This is in OpenSCAD, a script-based CAD tool that lets you define stuff in a script, rather than drawing it on the screen.  I find it easier to express specific dimensions such as this dome-boiler interface in text commands that can be edited more easily than mousing around on the screen.  The whole steam dome is described in 92 lines, and I've since found a simpler way to do the base than you see here

If metal is really what  you want to do, Shapeways offers a cast-brass option, a bit pricey, but the results are sure pretty...

I've described all this because I've found that, while there's a bunch of HOn3 parts out there for printing, the selection is based on the interests of specific modelers, so chances of finding your specific thing is rather small.  Me, I couldn't find Baldwin T-12 domes, so I had to script my own.  It's not that hard once you learn the ropes, but it's a barrier to using 3D printing as a machining alternative...

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