I've used Scale Hardware 1 mm rivets and 0.8 mm nuts as fishplate fixings. Their dimensional consistency and finish are excellent and they worked very well. I have given some thought to using them for loco rivets, instead of embossing.
Here's my version of the scale equivalents of the various sizes on offer... ( to the nearest imperial size. )
0.4 mm ........ 11/16" but would do for 5/8" or 3/4".
0.5 mm ..........7/8" " " " " 3/4" or 1"
0.7 mm ..........1 3/16" " " " " 1 1/4"
0.8 mm ..........1 3/8" " " " " 1 1/2"
1.0 mm ...........1 11/16" " " " " 1 5/8" or 1 3/4".
That's the easy bit...... the hard part is establishing the correct size for a given situation.
As an almost meaningless generalisation, the larger or thicker the component the larger the rivet size. Thus on my Fry Sentinel the body panel fixings were measured at 1/2" or 5/8" rivets, (or screw heads or nuts ) ; while the frame fixings are 1 1/4". Measuring the real thing is pretty reliable , just watch out for modern replacements on restored examples. A visit to a preservation society, armed with a pair of callipers and ruler, would provide a lot of useful information, if not for the exact chosen subject then something similar to get an idea.
Drawings.. particularly GAs... often give rivet sizes; but these usually indicate the stem size not the head. I have a drawing for an early GER loco which gives the tank rivetting as 3/8", but also the head size as 5/8" , suggesting that the rivet head might be estimated as 2/3 s larger than the stem? So the rivets attaching the hornblocks to the frames on a 'Claud Hamilton' are given as 7/8" , suggesting a head of around 1 3/8", or 0.8 mm in 7mm.
The same principles apply to the threaded and simulated hex nuts and bolts. The 0.8mm threaded nuts have an AF of about a scale 2", and are visible as nuts ... the 0.5 mm nuts are so small I haven't taken them out of the packet.
I have to admit that I can barely make out that they are hexagons without a magnifying glass. The difference is that nuts are flat 'headed', rivets are domed.... so for nuts around an inch or less, wire pegs are an acceptable representation.
Thinking about their use on the model...... they can give a much crisper effect than embossing, but they require sometimes very small holes, with the same need for accuracy as embossing, and they also have to be soldered. I recommend an RSU, and lots of practice at applying miniscule amounts of solder cream.
For the smaller sizes for body panels etc I shall continue to use the embossing technique, and use the rivets and nuts for the larger frame fixings, where they are sufficiently visible to make it worth while.
