dickon
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Re: To the Raspberry Zero Production line...

Thu Aug 08, 2019 9:26 pm

The original Pi 1B didn't have any at all.

plugwash
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Re: To the Raspberry Zero Production line...

Thu Aug 08, 2019 9:27 pm

jbeale wrote:
Thu Aug 08, 2019 9:23 pm
FWIW: 2.5 mm standoffs in black nylon https://www.amazon.com/Female-Standoff- ... 07D5T1TXV/
240 pieces
240 peices total in the box, but only 80 of them are standoffs, the rest of them are screws and nuts.

Still not a bad deal if you don't care about the length or you want a mixture of lengths.

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Imperf3kt
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Re: To the Raspberry Zero Production line...

Thu Aug 08, 2019 9:48 pm

bensimmo wrote:
Thu Aug 08, 2019 8:52 am
I can't make 3mm smaller.
And I can't buy 2.5mm screws, they're next to impossible to find except internationally. Buying a screw with a larger head is easier than making a 3mm screw shrink to 2.5mm

Though, last I measured, the holes are 2.8mm - M3 screws right in with enough force.

I'm indifferent to what happens regarding the holes. I'd prefer 3mm holes, but drilling them out myself isn't hard at all and not drilling the holes out usually gives me something to thread the screw into for additional gripping strength.
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Re: To the Raspberry Zero Production line...

Thu Aug 08, 2019 10:21 pm

scruss wrote:
Thu Aug 08, 2019 5:07 pm
ISO 261 and ISO 262 metric screw sizes are based on the R10 and R5 series.
For sufficiently loose values of "based on". It seems that the ISO 261 "first choice" values are based on a R10 series but rounded inconsistently. The "second choice" values seem to be based on R20 but with some values missing.

Both M2.5 and M3 are considered by ISO 261 to be "first choice" sizes, I haven't found a free list of what sizes are in ISO 262.

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scruss
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 2:27 am

Rounded to nearest even mm and they're R10
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rin67630
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 5:11 am

scruss wrote:
Fri Aug 09, 2019 2:27 am
Rounded to nearest even mm and they're R10
Then 3mm is the right dimension! Rounded to nearest even mm... :lol:

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rin67630
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 5:45 am

The basic problem is to fix the PCB into standard IP67 industrial cases.
The holder pads inside are all designed for 3mm* screws. 2,5mm is too lose. You must use them to keep the IP rating.
By the way the Arduino PCBS that I use as well are drilled to 3mm.

*which is ~ equal to 1/8 inches: a very common size in USA.
2,5mm would have been 1/10 inches. Try to buy that in a store...

But I'm fine with drilling the PCB to 3mm.

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Greg Erskine
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 6:39 am

plugwash wrote:
Thu Aug 08, 2019 3:06 pm
I suspect the issue is the clearances needed to make sure that even with a slightly oversized screwhead/spacer body and a screw/spacer not perfectly aligned on the hole that it can't accidentally short anything out.
Also, changing the hole size would need to go back to the PCB designer. PCB software automatically sets/checks clearances between holes and traces. A small increase in hole size *may* cause a lot of grief for the PCB designer. Bigger holes = less PCB space for traces.

While people drilling out the holes may work OK, it *may* technically breach hole/trace clearance rules within the PCB software.
* Raspberry Pi is a trademark of the Raspberry Pi Foundation

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rin67630
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 10:47 am

Greg Erskine wrote:
Fri Aug 09, 2019 6:39 am
Also, changing the hole size would need to go back to the PCB designer. PCB software automatically sets/checks clearances between holes and traces. A small increase in hole size *may* cause a lot of grief for the PCB designer. Bigger holes = less PCB space for traces.
Good point, thank you!

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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 11:42 am

davidcoton wrote:
Thu Aug 08, 2019 8:58 pm
scruss wrote:
Thu Aug 08, 2019 8:55 pm
At least you're lucky in that half of you hardware doesn't come with Robertson square-drive heads. They're a peculiarly Canadian thing, mostly for wood screws, but sometimes you'll find them on machine screws.
That's nothing. We get Torx, Hex, even crosshead clones that are neither Philips nor Pozidrive. And that's before anyone starts on the special security versions.
Don't diss Torq, it's a spectacularly effective system, able to apply large amounts of torque, unlike hex.
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 12:11 pm

jamesh wrote:
Fri Aug 09, 2019 11:42 am
Don't diss Torq, it's a spectacularly effective system, able to apply large amounts of torque, unlike hex.
I have nothing against Torx. I hate the number of different standards (and non-standards) that result in a health-endangering weight in my toolbox, because I need to carry a variety of sizes for each of five different systems. Especially for those that are insulated to VDE standard, which makes for chunkier tools even before the insulation is added.
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Re: To the Raspberry Zero Production line...

Fri Aug 09, 2019 12:16 pm

rin67630 wrote:
Fri Aug 09, 2019 5:45 am
The holder pads inside are all designed for 3mm* screws. 2,5mm is too lose. You must use them to keep the IP rating.
Maybe I hung out too long with old and reprobate machinists, but 2.5 mm → 3 mm is one of the other uses for rolling papers. Tear off a thin strip, lick it, roll it round the too-small screw and jam it in place.

But yeah: spent more than enough time building IP6x casings for weather stations. Still didn't stop the ants in Jamaica eating through the cable glands, though.
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Imperf3kt
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Re: To the Raspberry Zero Production line...

Sun Aug 11, 2019 10:37 pm

Greg Erskine wrote:
Fri Aug 09, 2019 6:39 am
While people drilling out the holes may work OK, it *may* technically breach hole/trace clearance rules within the PCB software.
At that point, who cares?
The board is already manufactured and in the end user's hands. Breaking design rules is no longer of concern.

If you're worried people might accidentally drill through a trace, don't be there's several mm gap surrounding the holes, 0.5mm is well away from any trace.
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Gavinmc42
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Re: To the Raspberry Zero Production line...

Mon Aug 12, 2019 1:36 am

If you're worried people might accidentally drill through a trace, don't be there's several mm gap surrounding the holes, 0.5mm is well away from any trace.
The xray pictures show no copper near the mounting holes, so 0.5mm is nothing.
The heads of 3mm screws are a bit bigger than 2.5mm screws so I use insulated washers.
A ground plane copper around the holes might have helped as extra heat paths but could cause ground issues.
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Re: To the Raspberry Zero Production line...

Mon Aug 12, 2019 8:38 am

I drill them out to 3mm, no problem with that.
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Re: To the Raspberry Zero Production line...

Mon Aug 12, 2019 10:24 am

I have access to 2.0mm and 2.5mm stainless bolts/screws so no problem for me.
so far I have no need to enlarge the hole as my cases depend on the default size.

if I do need a bigger hole, I have a handy manual 3.0mm drill bit (a drill bit mounted to look like a precision screw driver), a few twist is all that is needed to enlarge the hole.

2.5mm resin screws are quite rare here, however I have ready access to 2.0mm resin screws and nuts (have some on stock)
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davidcoton
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Re: To the Raspberry Zero Production line...

Mon Aug 12, 2019 5:22 pm

LTolledo wrote:
Mon Aug 12, 2019 10:24 am

2.5mm resin screws are quite rare here, however I have ready access to 2.0mm resin screws and nuts (have some on stock)
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