Author Topic: GH CAD Resources Hub  (Read 324205 times)

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Offline twohands

  • Posts: 26
Re: GH CAD Resources Hub
« Reply #300 on: Thu, 11 March 2021, 11:49:11 »
Another question, I calculate a keycap as 18 * 18 mm for 1U, so standard safety gap between edges (of keycaps, or keycap-caseing) is 1,05mm, but is that really necessary? I'm looking for the balance between "as much as necessary, but not more".

Sorry for the necro - but did you ever get a satisfying result for this? Having dug through various forums (including this thread), the best I can find are some empirical measurements that Cherry can be as large as 18.4mm and SA can be as large as 18.15mm. My naive thinking of how to do a proper design of cap-cap spacing (or take 19.05mm as standard) or cap-case spacing (especially the radius) is to examine two things:
1. Manufactured keycap tolerance - e.g. we use 18mm nominal, but actually 18.1~18.5mm in practice for cherry. I'm thinking as a community we have a standard set of manufacturers/profiles we design for and we can aggregate that range.
2.  Displacement due to key stem wobble. Particularly for mx-style stems, this seems to have a lot of variability.

Is this the right way to think of this problem? From my understanding, most case designers use 19.05 as a rule of thumb, but even that is a statement that the maximal size is 19.05 (or maximal size + maximal displacement). And some designers actually throw in an additional 0.5mm for cap-case gap, but is that a rough guess or actually guided by some principle?

I think probably this discussion doesn't matter to most case designers, as there's plenty of space to increase that maximal value in most 60%,65%,75%,TKL,etc. keyboards. This does matter to designers of high-profile thumb-cluster-based keyboards (Ergodox, Redox, Corne, etc.). The gap between thumb-cluster and the rest of the keys is generally a small triangular shape: it would look weird if a high-profile case left that gap empty, but at the same time the minimum width between keys is not high. See example attached. It makes sense to make that minimum width as large as possible to increase structural integrity of that "triangular peninsula".