Hi Chaps,
I want to make some "turnbuckle" style control rods for my RC toy aeroplanes but I am stuck for a technique / tool for making them. For those who don't know, the items I'm referring to are ally rods threaded at both ends, one end with a rh thread, t'other with a lh thread. This means that when the rod is turned the fittings screwed to either end move together or move apart. This saves having to detach one of the fittings to adjust the linkage. Making these threads is not the issue at all, I know how to do that.
The problem is I want them to be thicker in the middle than at the ends. But they are pretty thin anyway (say 5mm in the centre, tapering to 3mm at the ends) and they are around 200 mm long. This means that any attempt to taper turn them is doomed because you can't use the normal travelling steady on a taper, and they are so thin they'll just bend.
So my question is : Is there a taper turning mechanism that allows the tool to move back while at the same time the steady moves in the opposite direction ? (ie the tool and steady either move closer, or further apart).
I have vague ideas in my head about maybe having the steady and toolpost on the same slide but each having oppisite handed nuts and the feedscrew being comprised of two sections of lh and rh thread. This would give the motion I require, provided this feedscrew could be driven at an adjustable proportion of the lathes' main leadscrew rotation rate (so I can set the taper).
Anyway, I just wondered if there is a mechanism like this (maybe in an old ME ?), or if anyone has any ideas about it ?
Thanks,
Boo