I was jokingly thinking about details I could include on these pages and I thought I’d see how interesting screws could be. The answer after a few paragraphs is not particularly. I looked to see if there were people out there who collected screws. They would love this stuff, alas I couldn’t find anything.
Screws. There are lots of them. All electronics products use them. We only have to get personal with them once something breaks.
The ZX Spectrum Next uses four different screw types. In the BOM (Bill of Materials) they are listed as items 20, 21, 22 and 23. So we know what the design states, but that then requires proving each screw type in the real world.
Item 20 – Machine Screws M3 x 10 posi-pan – 6 per unit – 18,000 required – these secure the top and bottom case sections via threaded inserts.
Item 21 – Plastite screws M3 x 8 posi-pan – 8 per unit – 24,000 required – these secure the motherboard and daughterboard to the top case section. These were originally 10mm but were found to be too long for a couple of the screw positions.
Item 22 – Plastite screws M3 x 6 posi-pan – 1 per unit – 1300 required – these secure the Raspberry Pi Zero blanking place (where applicable).
Item 23 – Wafer head machine screw M3 x 4 – 10 per unit – 30,000 required – these secure the keyboard to the top case
I make that 73,300 screws in total! When you have that much of something you have to talk about it.
Where to buy all these screws? It depends on who is going to be using them. Do we merge the case and keyboard in China in which case we either buy the screws in the UK and ship them to China, or we source screws in China, what are the differences in cost? £1644 for one of the sets sourced from the UK or $1800 from China. What’s the exchange rate today???
Actually this scenario happens quite frequently. When there isn’t much in it then we side with a UK company (even if they’re actually made in China originally!). In the case of deciding what to do in the UK and what to do in China, often it is down to cost although sometimes logistics make things difficult and force you down a particular route. Especially in China, shipping “goods” between factories carries a price, effectively a domestic shipping tax, although if you ship to Hong Kong then you’re fine.
Each of these screw types needed to be sourced and tested. For that we need a completed case and a keyboard. As our case requires threaded inserts, we have to source various types and test them out in the cases. Then we need to send them to our case manufacturer in order that they can work out the best method for inserting them. As part of the moulding process which requires tooling, or cold pressed after the fact, or ultrasonically.
So ultimately we work out who will be doing what, SMS, keyboard partner or case partner and then order appropriately 🙂
I’ll probably get back onto the case stuff because this section is a bit of a let down. Like an episode of your favourite show when there has been a writers strike.