Scale Fastener Choice?

Hi

I am planning to build a miniature steam wagon with a scale of about 4". The original 1925 prototype probably used BSW fasteners. For me the most accessible range of fasteners are metric.

What do others use for scaled models?

Dazz

For the sort of sizes on a 4" then the commonly used BA won't get much use so something like BSF would be a reasonable choice particularly if you need to put a thread on the end of a stock imperial size rod.

As you say metric are easier to get hold of but the commercial heads do tend to look a bit flatter than old Whit ones and you get that nasty grade stamped into the top. You can get small hex metric but again like the BA won't go upto the sizes you are likely to need.

Ideal thing is to make your own with a nice scale looking head with single chamfer which will also be crisper than the forged commercial fixings.

I've recently finished off a 1/3rd and 1/2 scale engine that had been started with metric threads. I may get shot down for this but I made all the nuts and bolts with imperial sizes base on 1/16" of hex for 1mm of thread diameter and they look quite a nice size with a what is in effect a hex of 1.6D.

I tend to use metric (cheaper) but have reasonable stocks of both metric and imperial fasteners. I just use what's to hand, and if appearance is important, I'll happily use a BA nut re-threaded with a larger metric thread. (Metric nuts are too thin to look right.) Where fasteners aren't immediately visible, I use metric cap-head screws for their strength and ready availability.

Metric hexagon screws are usually quite large in the head department, but that just means that they mimic the large head pre-war Whitworth AF to thread diameter quite well! You can always just skim off the "M 8.8" markings if it offends you - or make your own! However, their head height is, like the nuts, a bit thin for correct Whitworth appearance.

(Avoid imperial hexagon-socket countersunk screws at all costs - the size of the hexagon socket is too small to apply any serious torque to the screw. Metric ones are a lot better in that respect - but you still need a well-fitting, unworn Allen key.)

Hi

Where I live, metric is easy. Anything else is really difficult. I might be able to find Whitworth but no chance for BA.

So for visible nuts, making metric versions is probably the best option for me.

I cannot conceive why so many traction engine designs specify BSF threads, and all the lemmings gaily follow this edict over the cliff. The result is that they pay massively over the odds for all the fasteners, and are limited to a very small number of suppliers.

My current (self designed) project is all metric which makes life easy. My previous project (4" Burrell) specified BSF fasteners throughout. I went with UNF - quite a similar thread, but I could wander down to my local fastener stockist and get all the necessary over the counter for very reasonable dosh. I suspect that even UNF / UNC is getting harder to find these days.

Martin

Probably due to the fact they were designed 40-50yrs ago when metric was not so commonly used and you could easily pick up BSF fixings. Also far easier to put an imperial thread onto all the imperial diameters on the imperial drawings.

Oh dear, leeming here.

Mind you I do make all my own BSF (plus BSP and some BA) nuts, bolts and studs where they are on show. I'm about to order some more BSF nuts, but they're for the home made 'rivets' holding the smokebox to the boiler, and thus won't be seen. For hidden stuff, mainly within the gear train, I use metric SHCS with whatever head is appropriate. There are also one or two UNF threads on my engines. The ones that spring to mind are 5/8" UNF holding parts of the gear change mechanism together, as I needed a large fine pitch thread.

Andrew