Metric hardware and models
I recently finished building my MK3S kit and would like to start some of my own projects. For some of them, the metric screws and nuts Prusa used would be great for joining parts. Especially since I got some nice Wera drivers to use instead of the Allen keys. Where is a good source (that is US-based or ships to the US) for various sizes of this metric hardware?
Also, is there a place to find the 3-d modelling for using these parts? For example, the hexagonal nut-capture holes, and precise recess holes for bolt heads. These shapes look easy enough to model from scratch, but I'm not sure I could do it precisely enough. For another example, sometimes a bolt is driven into a hole that is just the right amount smaller than the bolt diameter, so the threads cut into the plastic. Too small and it won't screw in, but too large and it will be too loose.
RE: Metric hardware and models
I get my nuts and screws from Ebay,
Prusa use Stainless Steel M3 Nuts Screws and Washers.
please note there are normal and thin metric hex nuts and square nuts... Prusa use the thin nuts. 
Regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Metric hardware and models
@joantabb
Thanks! I'll look for those on Ebay.
RE: Metric hardware and models
@ec1
Search for "DIN 562 M3 A2". Another possibility is to use threadinserts like this one -> https://www.bondtech.se/en/product/thread-inserts/
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Metric hardware and models
@karl-herbert
Thanks! I found numerous vendors right away. I thought I might stock up with a small supply, and some of the bolts in various lengths.
RE: Metric hardware and models
McMaster-Carr is a great source for hardware in the US. A bit expensive and you often have to buy packs of 10-100, but they have a great selection, and if you happen to be near a distribution center, very fast shipping or pickup. They also have drawings and downloadable 3D models for just about every piece of hardware they sell.
@joantabb
Do you happen to know why Prusa is using all stainless hardware? This puzzled me when I first realized. It seems an unnecessary expense.
RE: Metric hardware and models
DIN 563 M3 A2 stainless steel - €2.20 for 100 pieces
DIN 562 M3 FKL4 steel zinc plated - € 0.86 for 100 pieces
Of course you can also use galvanized or blank steel, everyone has to decide for himself.
Stainless steel is durable, corrosion resistant, temperature resistant, weldable, low maintenance, hygienic, etc.
As far as I know, Prusa only uses stainless steel fasteners and of course purchases the huge quantities at much lower prices.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Metric hardware and models
@incendium87
Hi,
I have to be absolutely honest and say I don't know...
Like you, I am a user, not a company employee.
Putting My 'Guessing hat' on I would suggest that it is a decision based on style and self preservation.
the use of Screws in Plastic, doesn't call for immense tensions, so the benefits of carbon steel are no real advantage whilst the propensity for carbon steel products to rust in a disadvantage.
Stainless steel screws are more aesthetically pleasing than carbon steel screws and they are cleaner to handle.
Stock will not corrode easily, maintaining it's value for extended periods,
During assembly Stainless screws and nuts tend to be easier to assemble than carbon steel equivalents.
Prusa try to reduce the number of dissimilar components to make cost and stock control easier, as such, the fixing requirements are engineered to use 'standard' length screws which are almost exclusively M3 (Metric 3mm screw thread) fittings
Note, (Guessing hat still on) there are two common thicknesses of square nut and hex nut, when assembling plastic parts the assembly torque / tensions required are easily handled by the thinner nuts, and this fact makes their integration into plastic assemblies, more convenient, simply because they require smaller openings in the housings, holes, generally reduce rigidity and strength of a component.
Plating, is not a good idea, because, Many plating options use metals that cause allergic reactions.
Stainless steel is unlikely to cause allergic reactions (I am wearing Stainless steel earrings, following allergic reactions to other metals)
this will potentially reduce customer complaints
Jo Prusa is known for making things to be seen... why else would he choose semi fluorescent orange contrasted with Black as his corporate colour scheme. Bright shiny fixings accent the features of the assembled components.
Of course, I could be totally wrong! 😀
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Metric hardware and models
@joantabb
Thank you for such a detailed and thought out reply. You make a bunch of great points. I guess the ease of use and improved aesthetics are worth it if they're buying in high enough numbers to bring the cost of stainless down.