Switch Plate Laser Cutting Tolerances

[malsyned]

The Cherry MX and Kailh BOX datasheets both specify plate cutout tolerances of 0.002" (0.05mm). However, a lot of laser cutting shops I'm considering using say their typical tolerance is 0.005" (0.125 mm), even ones recommended by mechanical keyboard hobbyists (like https://www.keebtalk.com/t/list-of-laser-cutting-services/2500).

How do you reconcile this? Are the datasheet tolerances unnecessarily conservative? Do most people just accept the 0.005" tolerances and usually it works out? Do you have to specifically request tighter tolerances in order to get a well-fitting plate? What's the deal?

[nevin]

it would probably depend more on what switches you're planning on using. there are some models from some brands that have a much tighter fit than cherry. figure out which you are planning on using and use the tolerance as part of your design for that specific switch.

unless you're doing a GB or something that you won't know what switches the user is going to put in the plate...
it shouldn't be a problem, because even the MX/ALPS cutout (supporting switchtop opening) will hold MX switches just fine, which is a lot less contact between the housing and the plate than a standard MX cutout without cutouts for switchtop opening.

[malsyned]

it would probably depend more on what switches you're planning on using.

I do know, I'm planning to use Kailh BOX, either Pink or Pale Blue (I have the pinks already but I'm having second thoughts). The spec sheets on NovelKeys show a tolerance of 0.05 mm on them.

there are some models from some brands that have a much tighter fit than cherry.

This is where I get confused. You say that Cherry have a loose fit, but the Cherry MX datasheet on SparkFun specifies the same tolerance (but in inches as 0.002").

it shouldn't be a problem, because even the MX/ALPS cutout (supporting switchtop opening) will hold MX switches just fine, which is a lot less contact between the housing and the plate than a standard MX cutout without cutouts for switchtop opening.

Are you saying that cutting to 0.005" tolerances won't be a problem for a standard MX cutout, based on the fact that even the combined MX/ALPS cutout works and it's way wider in the X dimension?

I am planning on using what swillkb calls the "MX Openable Cutout"

[nevin]

there are some of the gateron/novel keys variants that are known to be a tight fit in some plates that are ok for other MX variants. think it was due to slight tolerance differences in the housings of some of the "fancy" switches that have been coming out. (the "fancy" ones being ever so slightly larger than the standards, probably for better fit in loose hotswap boards).

the openable cutout only works for cherry & most gateron style housings (4 tabs that clip down on the lower part of the housing)
Kailh BOX switches use one long tab on either side of the switch. they are not openable once in a plate.

see what tolerances swill & the vendor they suggest (lasergist) uses and go with that.
- and don't forget to specify the correct kerf (width of the cutting tool) for the vendor you are planning to use. the vendor you want to use should be able to specify what value to use.

[malsyned]

the openable cutout only works for cherry & most gateron style housings (4 tabs that clip down on the lower part of the housing)
Kailh BOX switches use one long tab on either side of the switch. they are not openable once in a plate.

Oh that's good to know! Thanks, you just saved me a few bucks in laser cutting costs by simplifying my plate cuts. I'm using hot-swap sockets anyway, so I don't really need to be able to disassemble switches without removing them.

[nevin]

being hot swap. i wouldn't worry about the tolerances. wouldn't hurt if they were a little large.

[malsyned]

being hot swap. i wouldn't worry about the tolerances. wouldn't hurt if they were a little large.

Oh really? What about the hot swap sockets makes the plate tolerances less important?

[nevin]

not less important, just on hotswap boards, if the plate is too tight you won't be able to get the switch out or could damage the switch or plate trying to pry it out of the plate.

because you are using hotswap and are planning on trying different switches (reason for hotswap) you don't want a plate that's too tight.
- most off the shelf boards and even some kits have plates that are too loose and the switch comes out with the keycap when pulling a keycap.

[Bitdrive]

This is actually pretty useful I’ve also been struggling with this so I’m glad to Final another thread about it