Boring copper is boring!

To fit the large (42 mm) flues into the boiler tubeplates, I had to bore the holes, having no drill of that size - and no machine to handle one, had I had such a huge drill... Instead, I bored the holes using a resurrected inside cutting lathe tool - you can see that I've silver-soldered and sharpened an old indexable bit to the shank of the old tool:

Copper doesn't really cut, it deforms! Try as I did, I couldn't get the tool sharpened to a suitable form and angle (on a "green" stone, which does grind indexable bits, albeit slowly), so that I'd get nice swarf - instead, if the feed was more than a few tenths of a mm, the copper expanded over the edge of the tool! I tried both oil and alcohol as a cutting fluid - the latter did help a bit. So, going slow and steady, and using a minuscle feed... it took me a whole day to turn the outside diameter of the flanges and bore the holes in the two tubeplates - but:

The boiler is taking shape! You can see the dry tube on top, three tube stays - which will contain a throttle rod & possibly a blower line, not that I think I'll need a blower, with the planned firing system... The hole in the middle is for the lower blowout valve for the water glass - the upper one will connect to the dry tube.

If you wonder why the color of the shell tube is slightly different from the rest - well, it is cupro-nickel! Called CuNiFer, its used in shipboard steam generators and heat exchangers, for instance. It has an annealed tensile strength two times as high as copper, is very ductile, corrosion resistant - in fact, all its properties are "better" than pure copper's, except two:

1: Heat conduction is about one tenth of copper's - but since this is the outside boiler shell, in this case it is actually better - for firebox or flues, it would be worse. Thermal expansion is only about 2% more than copper's: 17.1 um m-1 K-1 vs 16.8 for copper so I see no problem there.

2: Cost... That didn't apply in this case, though, thanks to a benefactor... :-)

Tomorrow, I'll start turning some fittings of bronze for the water glass, steam manifolds (one at each end of the boiler), feedwater inlet blowout cock and steam dome. After that, it'll be time for some hot work, silver soldering the whole kaboodle...

Close this window when you are ready...

Any information presented on this website (especially any do-it-yourself instructions) is given without any acceptance of liability for damage or injury - so, always remember: SAFETY FIRST!

The material on this page and its related pages is Copyright © 2001-2007 by J-E Nystrom. You may NOT copy, transmit and/or publish any of my images or texts in print, electronically, on your own website or in any other way. The author retains all rights to this work, with this sole exception: Storing the pages on your own computer or printing out a paper copy, for your own, strictly personal use is allowed.

You may, however, freely link to the "Building Live Steam Locomotives" page at:, or to my Animation Home Page at:

You should NOT link directly to THIS page, since it's address may change in the future. Also, you may not put any of these pages or pictures into "frames" on your own website.

Thank you.