"Andrew VK3BFA" wrote in message
ups.com...
| Hi All,
| new to this metalworking stuff, so please excuse my stupid newby
| questions. I am trying to build an HF Yagi antenna from telescoping
| aluminium tubing(to reduce windloading and weight) - trouble is,
| Imperial size tubing was a good fit into the next size ID, so
| telescopic sections could be made easily. All thats available now is
| Metric sizing, and its too sloppy a fit into the next size up. HOW do I
| roll/reduce the diameter of the bigger tubing so its a nice
| interference fit onto the smaller size down? -

Take the blade out of a roller pipe cutter. Spin it around a few times,
keeping it tight, then measure where it is. Slow but it works for me. To
swell out the pipe, and if its the right size, use an exhaust pipe mandrel
expander tool, from your usual auto parts stores. For smaller sizes, put in
your vise a hard rod slightly smaller than your pipe. Start hammering on
the pipe and the metal will swell out where you've been hammering. Takes
awhile to get the hang of it, though.