Here in the UK, we use metric fasteners. When you go shopping for small screws though, the only sizes you can generally get below M3 are old, awkward imperial sizes. Even if you are happy with M3, the variety of shapes and lengths is woefully inadequate. Imagine my delight when I found perfect screws on Amazon of all places.
Apparently widely available in Japan are metric screws with very shallow heads. These are ideal for many tasks in small robots but almost impossible to find here. Not so easy in the USA either I believe. After taking out a laptop hard drive, I realised that the screws holding the drive into the carrier were exactly what I wanted. Out of curiosity, I looked in Amazon for “laptop screws” and came across these:
They sell a pack of 156 screws of exactly the type I wanted in M2, M2.5 and M3 in a variety of lengths. Their entire range covers nearly everything I need. Excellent!
It is very difficult to find metric screws in the US.
The screws with thin heads are the JCIS screws that are used in cameras. I ended up finding them from a RC helicopter place in China.
It’s impossible to find anything M3 or smaller in hardware stores here. Probably hobby shops but then cost is exorbitant. I’ve had luck getting metric screws from ebay but mostly look at smallparts.com first. They have a bunch of other cool stuff. I also get the big packs of #4 hardware from Radio Shack (e.g., 64-3011).
I was so happy when i found a nautical shop here in Slovenia that has all possible screws: http://kamm.si/katalogi/katalog_vijaki.pdf
Basically all in stock. I love to go to that shop!