On Mon, Mar 9, 2020 at 11:49 PM, Mehmood wrote:
Thanks very much for the offer of the RP25 wheel profiling form tool Keith, that's very kind, again!? However the profile I need is for P4, smaller and narrower.? The method you described seeing, slotting out the gaps between the spokes, is exactly what I had in mind, with the traction tyre fitting closely around the exposed spoke ends.? I haven't done it before, myself, so I'm feeling my way.? I would be really interested in a discussion on form tools though, because I don't have a metalworking or practical engineering background - sadly such things were looked down upon from the academic stream of my old grammar school - my great, lifelong loss!? There was a brief article on the subject in a 1960s model railway magazine probably by the esteemed Colin Binnie, but I would need to know everything from the basics - what kind of steel to use, how to shape it (obvious if it's your line of work, but I could waste a lot of time and enthusiasm between grinding, sawing, filing etc), how to profile the rake according to the product material (mild steel in the case of traction tyres), how to temper it, and while in use, how to part off either incorporated into the form-tool or separately.? Also the cutting is different anyway - with conventional turning, the contact is usually at a pinpoint, but when the form tool is well into the work, it is cutting a multi-sided strip out.? So thoughts and experience on form tools in the relatively small Unimat would be interesting.
Well you're not far away from me, so I should pop in. Colin Binnie would happily make anything like that. He was one of the less famous but notable model makers of his era, perhaps because he didn't (to my knowledge) write books about it. I met him a few times in the late 60s, and he was always using his skills to make superb models, and with plenty of stories about the things that went wrong. I think he had access to some pretty sophisticated tools at work. I know how I'd make a form tool if money was no object, but making something that small at home is another matter. It can be done, I'm sure. you'd have to accept several duds as you get the hang of it!
Keith
