kicad-developers team mailing list archive

[Alex G <mr.nuke.me@xxxxxxxxx>]

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>>>> a hole of 3.2mm. I know the pad is 3.2mm, but when generating drill
>>>> files, the hole size will be the size of the hole, not that of the
>>>> drill. That's not a big problem when drilling manually, but when using a
>>>> CNC, especially with auto-tool-change, it can give the engineer quite a
>>>> few headaches.
>> 
>> In drill files the tool specified is *always* the finished hole, no
>> exceptions. This is because PCB drills usually are actually cutters and
>> special
>> compensation applies. And of course there is plating which is a process
>> variable, too. Buried and blind vias are another kind of hole too, but
>> anyway you just state the *finished* hole size.
>> 
I meant "will be the size of the hole, not that of the PAD". That was
when the hole size was 0.6mm. Now it's fixed.

>>>> The recommended hole size varies between manufacturers, but all
>>>> datasheets that I've consulted "stated" "compatibility" with 3.2mm
>>>> holes. (Amphenol: 3.2+- 0.126; Harting: 3.1+-0.1, etc).
>> 
>> I agree. It's actually an imperial hole size but since boardlock is
>> usually elastic or a fixating screw/rivet, there is a good tolerance.
>> Slimline connectors are more picky...
>> 
>>> Referring exactly to the pad size for an M3 nut without washer.
>>> The general rule I use is
>>> Max component size + Screw in hole tolerance + Other tolerance (like
>>> washer to screw) + some random value (0.2 mm :) )
>>> The following would amass to (M3 screw in 3.2mm hole)
>>> Screw only:    6.4mm
>>> Nut:        6.8mm
>>> Washer        7.4mm
>>> The last one doesn't exactly follow the formula above; if it did, the
>>> full-body-condom--safe pad size for an M3 washer would be 7.8mm (a 3.4mm
>>> ID washer fitting over an M3 thread add the 0.4). I don't think anyone
>>> will need as much torque to justify a washer, so 6.8mm should be fine.
>> 
>> There is a standard for these too... you can use the LP calculator,
>> which gives hole/pad/clearance for mechanical fixturing:D
>> 
>> Of course these are sizes absolutely not criticals and often compatible
>> connectors (i.e. Tyco vs Molex) states different sizes but are actually
>> interchangeable...
>> 

Sorry for being google-lazy, but do you have a link to the LP calculator
you mentioned? The one I keep being pointed to requires the purchase of
some awkwardly named standard.

>> I have a whole series of picoflex, spox and phoenix terminal blocks already
>> done, if you want them. They should be on my bzr on launchpad. No idea
>> if they fit your lib conventions, I have mine.
>> 
Thanks! I'll check it out.

>>> I'll try to see if I can get this info from suppliers.
>> 
>> Panasonic gives them.

Already linked that in a previous email (cc'd on the list).

Alex

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