The possibilities are probably endless. In fact, it would make quite a good subject for a competition. "Who can design & build something to make such a thread, in the simplest way?" alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx www.alanstepney.info Model Engineering, Steam Engine, and Railway technical pages. ----- Original Message ----- From: "Roger Mason" <roger.g3tdm@xxxxxxxxxx> To: <modeleng@xxxxxxxxxxxxx> Sent: Thursday, October 14, 2004 5:08 PM Subject: [modeleng] Re: Another question Hi, Peter asked: >Any ideas on how to cut a variable pitch spiral on a round rod? > The obvious one is CNC. If that is not possible - how about a cam driven saddle? or How about the saddle moved along the bed by a lever system, which in turn is driven by the normal leadscrew. As the lever gets to be at right angles to the motion the speed along the bed increases. or I am sure a fusee could be used in some way, perhaps driving the leadscrew on the lathe. Alternatively any of these ideas might be used to move the ferrite (or whatever) to alter the inductance in the electronic device you are working on, and obtain the linear frequency/displacement curve that way? I thought these days it was all done with PLL's, but perhaps this coil is not on the oscillator side. Can I try out the communications set when it is finished? ;-) There is a spare saddle for a Myford on e-Bay at the moment - just right for such experiments. The project sounds to be interesting - need any further expertise? Cheers, Roger Mason, G3TDM, in St. Agnes. MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.