Model Engineers Threads

Metric threads are virtually unknown in  model engineering here in the UK and in the USA, but that's not the case everywhere. The hexagonal heads of Model Engineers bolts are of a reduced size and these are readily avaliable from companies like Reeves.

For some reason, the same hasn't been done in the UK for Metric sizes, and this may be in part due to the fact that Metric Coarse Threads are often unsuitable on larger sizes where a finer pitch is required. It seems less well known that the Metric system of threads also defines prefered finer pitches. Taps and dies for these sizes are available at reasonable cost.

Threads for SPEEDY
Naturally if you have a stock of Imperial sized fastenings and the taps and dies to go with them, it makes sense to use them, but for newcomers there is an alternative. Companies such as KNUPFER in Germany have a full range of Metric fasteners with reduced heads for Model Engineers and they are reasonably priced and shipped worldwide. Some sizes are also available through Polly Model Engineering.

Most of the BA sizes have very close equvalents to Metric Coarse Threads and the finer ones can mostly be replaced by the prefered Metric Fine Threads.

Thread sizes start at M1.2 through M1.4, M1.6, M2 & M2.5 with model engineers reduced head fastenings available up to M4. The chart shows the most commonly used Imperial sizes with their possible Metric replacements.

Scale bolts
If you know the original size of the thread on the full size locomotive, you can find the appropriate Metric equivalent from the tables here.