Rationale for ME type threads ?

As the name suggests, they were designed for model engineers to produce scale looking threads. A small screw of standard thread form looks like a small screw, not a scaled down version of a big screw. I think it is purely a visual thing, like the BA nuts & bolts you can buy with smaller than standard heads on them.

Regards

Kevin

One great another advantage ME threads have is for blind boiler longitudinal stay nuts. When running then on there is no danger of putting any stress on the stay, backhead or tubeplate.

They also give you a second chance if you tear a thread since they can be obtained (sometimes) in 1/32" increments.

Thanks to you both for the replies,