So, earlier this week the drill bit set arrived-- A couple of points, first, on that:

It really, for the cost, is not a bad set. That said, seeing as I do not yet have a full CNC setup and have never worked with such small bits before, a couple of things to point out.

For one, it is not even worth bothering trying to use PCB bits without a drill press-- in all of two seconds, they will just break. I knew this up front, but even with the sort of shaky drill-press I have (while the Y axis is tight, the X axis has a tendency to 'float' due to vibrations when the drill is 'on'), a couple of other experiences worth mentioning.

Typically, when using a soft bit into a hard material, you can (or may even need to, especially if the bit is not sharp enough) perform a series of successive presses into the material-- part of the reason being to remove any extracted material from the bit, to keep it from completely seizing up in the hole.

However, that just doesn't work in this case, either because of the strength of the bits themselves, or that the tolerances are just so small. Ultimately, it is sideways torsion, less than downward force that will cause a bit to snap, and out of the box I broke two testing this process (also, for that reason, always remember to wear protective eye-wear).

So, what I found is that while yes, it is key to 'steady' or support the PCB from underneath while on the press, unless you have some sort of uniform type of solid sacrificial support, such as engineering foam, regardless, under the pressure of the drill, with a large enough sized board, it will start to bend.

The immediate tendency then is to back off-- but don't-- Go careful and, as always, slowly and the bit won't snap and you'll have a nice drill out.

The Learning Process

However, unfortunately with the success of this step, I also had gained some confidence with re-soldering the cheaply attached rocker switch, and though everything functionally on the phone was working at that point, some wires had already started to come of the much larger 'bus' wire assembly, so I decided simply to cut, strip and rework that too.

Yet, this is/was/has proved to be a mistake. Good soldering truly is a skill which I take every opportunity to improve at. However, it rather is a 'lost art' in the similar sense that 'wire wrap' once was one-- Or in technology, if never 'Art', certain methods are rather obsolete, especially as more and more packages arrive on the market only in BGA, or in SMT, or 'surface mount', are already amenable to the much simpler process of reflow.

-- Enough of feeling 'slightly defensive'-- After the rework process, and not, I believe, because of the drill-out, unless there is some hidden ground plane unseen, the dial buttons on the keypad are no longer tripping by jumping the circuit as they used to.

Given this setback, I feel it was actually useful, as I have been able to consider both the project itself and it's ultimate goals. Originally I thought of this project as something any very 'young' budding RasPi 'engineer', could DIY, or go above making just another video game emulator, but the cutting and the drilling and the like....

So, yes, hunting around on the board, I am confident I could discover/find/resolve the apparent short connection-- But back for a moment in the learning process in all this:

As mentioned earlier, this board is a combination of through-hole and SMT, together really aimed at minimizing cost (or cents of cents on the dollar), in kind of an interesting way-- Hobby or low scale production products usually tend to be just one or the other.

However, almost all through hole applications are either plated through-hole, both for the sake of 'inter-board connections'-- And, while I have never quite been a fan, though this is definitely why the iPhone always costs, somewhat, so much, and though of course this is SMT, between the two obvious 'green' layers of chips on the front of the board, there are at least 14 additional layers, of power, ground, and signaling, sandwiched in between, and even today, at scale this remains rather costly to produce.

But, even if you are not seeking sandwiched connections, plated also helps because, conducting heat, it draws in the solder, from one side of the board to another, completing the connection.

However, not only are the through holes on this phone board 'not plated', but even the top conductive ring layer seems as if it may have been only just substantiated with an impressed solder layer-- Or pulling the wires out with the solder sucker, one or two traces actually 'lifted off the board' in the process, and though I do have some solderwick, and that would be the more recommended approach, in the moment I thought a bit 'Who came up with this cheap shit?!?'

So with a bit of distance and time away from the project (though ever present, more like percolating thoughts), I realized more to 'think like an engineer': Or just what are my goals, aims ?

From a 'design' point of view I liked the concept of this one phone being able to contain everything with little surface modification... But, it requires more work than is actually needed, and likely excludes many devices one already has-- thus the thought and the 'new point of attack'.

All this device really needs to do is both 'listen in' (for the sake of voice commands) and 'perform dialing'.

First part, 'really easy':

For the second half, for dialing, the board needs to be able to output sufficient DTMF tones and thankfully the RasPi model B has two PWM modules broken out to the headers-- Though, admittedly, I don't know quite yet if I can manage to pulse the two directly, need to build a small additional R-2R ladder circuit, require a fledged DAC chip. There are, of course, full-fledged IC's for this purpose...

And of course, this project is for my grandmother, whose 100th birthday is in just over two weeks, but I realize the facts, that someone much younger, whomever they know who might need such assistance, might pick up the guidelines of the project, or even better, go further with it.