Comment by voidUpdate
22 days ago
I'd be interested to know how BMW manufactures those screws. The patterns in the metal in the image suggest the entire hole was drilled out? The deepest part has circular marks inside that looks like the marks left by a facing tool on a lathe or similar. Then I guess the two wedges were inserted and the whole screw faced?
Unlike all the other guesses here, I actually do have experience with manufacturing specialty aerospace fasteners similar in size, shape, complexity, and precision as these. These are most assuredly being manufactured on a specialty tool called a “Swissing Lathe”, or Swiss CNC machine, because that is the machine you always use to make parts like this. It is a multi-headed turret mill combined with a lathe that can continuously feed a piece of long bar stock and continually spit out fasteners. They were invented many years ago to produce extremely high precision small screws for watches, and in fact Citizen is one of the main vendors of these tools to this day. Based on my experience I would expect the cycle time for making this part to be 30 seconds or so.
Here’s a good video that eli5’s the difference between a Swiss screw machine and conventional CNC.
https://youtu.be/y3y0tATB0lg?si=pkYDT3BV0-6C-aq5
And here’s a video with a high quality soundtrack that shows how the machine combines automatic lathe cuts, mill cuts, and thread rolling without changing machines, swapping cutters, or re-fixturing the work.
https://youtu.be/MPAK5I1HJAw?si=fnMmjDp6ydYSDbfH
And if you need some specialty fasteners made and have an unlimited budget I can reccomed these folks.
https://centrix-us.com/
CNC Milled and suface brushed. I Think these screws are going to be used in some decorative Panels etc. Would be cost prohibitive to use these all over the Car.
This. It's obviously an interior fastener. Maybe they'll have a cheaper one without the logo for the airbag module or whatever. OEMs have spent untold sums over the year hiding interior trim fasteners using all manner of push and snap fittings. A few low trim vehicles have bucked that trend recently, to much savings of labor and tool/die cost and no apparent ill effect in the mind of consumers. And now everybody is testing the waters.
The prototypes might be milled and/or produced via additive manufacturing (3D printing.) In production the heads are likely formed via stamping. Here's an old video I remember watching as a kid (Unfortunately quite pixelated) of the Robertson screw being manufactured which has a tapered square profile for the bit: https://www.youtube.com/watch?v=Td7GjAMAY7Y (The Acme School of Stuff was awesome for its time and still is.)
The head was almost certainly milled out of a blank made on a lathe. Something like this: https://youtube.com/shorts/Yf-twqgWZQ8
I don't see any geometry that would be hard for casting or milling, it's slightly more expensive because you can't do it in one go, but you have to lift the toolhead if you mill.
Screws aren't cast. And lifting the toolhead takes about .1 second.
What's expensive here is milling this screw head at all, and in particular the surface finish.
This is probably just a prototype for shows, though. At scale, screws heads are usually cold-formed, and this design would work for that, too. If you circular brush the head in the end, you'd get pretty close to this, even if you wouldn't get the finish in the pockets. But that doesn't make much sense there anyway, it'd get damaged by the fastening tool.
For prototypes, almost certainly with a CNC lathe. For a large scale production, I would expect them to drop forge these...
Those are end mill marks.
Nearly zero chance of them doing that at production volumes though.
Why not? A properly set up CNC machining center would turn those out by the bucketload. That's precisely the sort of thing that BMW does regularly with exterior details, no reason why they couldn't do it for a batch of bolts.
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