Many thanks for the replies – nothing has changed.
I re-opened the tread because I have started designing a model steam engine. I decided it should be metric including fixtures. Tubal Cain, in his Model Engineer's Handbook, reports that this was discussed in 1981 and the BSI published a document Guidance on Metric Screw Threads and Fasteners for Use by Model Engineers, PD6507-1982. I have not seen this and I doubt if anyone else has (a copy costs over £100). Soon I have to make up my mind whether to stick to BA or take the plunge and go to metric.
I think, as JasonB suggests, this has serious implications for our hobby.
Posted by JasonB on 04/10/2019 07:16:45:
All the time people keep knocking out the same old locos that were designed years ago and following equally old drawings there will be little demand for all the ME suppliers to carry good quality small metric fasteners. The last 11 models I have designed and built are all dimentioned in metric, use metric stock and all have used fasteners from GHW if other designers do similar then demand will go up and suppliers will be more likely to add metric fasteners to their range.
It is probably wishful thinking that Stuarts would revise their 10 series drawings and offer a metric set along with metric fasteners and materials, same with the likes of Reeves or Sarik, I can't see them updating the beginners drawings to metric any time soon so beginners will be sucked into the BA & ME series system never to get out.
J
PS Michael, not ignoring your link as they are hex head screws
Edited By JasonB on 04/10/2019 07:19:33
Obviously there is little point in converting most models to metric since they are only made by the experienced. However the opposite is true for entry kits such as some Stuart models. To be presented with the drawing for a Stuart 7A can be quite a shock for someone who has only known metric units etc. I know from experience since my niece decided to make a Stuart 7A while in six form (the school had, probably still has, a well equipped workshop) fifteen years ago. With the help of her teacher all the dimensions were converted to mm but problems arose when it came to drill sizes. Neither of them had any idea about number drills and the usual shops (local, Axminster Tools) could not help. So uncle was phoned.
Perhaps someone should buy a popular Stuart model and try building it, with a blog, as a complete metric model with dimensions based on mm and not converted from fractions of an inch and with metric fixtures. Just a thought for the future of our hobby.
JA