18 Sep
2013
18 Sep
'13
4:08 p.m.
On Wed, Sep 18, 2013 at 5:57 PM, Al Kossow <aek at bitsavers.org> wrote:
On 9/18/13 1:01 PM, Fred Cisin wrote:
Howzbout a paper drill?
The problem I ran into was not getting perpendicular cuts through the foam
if I tried
cutting it without the shim stock attached, because the foam deforms and
bends to the side
as you force a leather or cigar punch through it. Also, if you look
carefully at a pad,
the foam is a slightly smaller diameter than the stiff plastic. If the
diameter of the foam
is too close to that of the stiff plastic, it is difficult
for it to clip into the little plastic tabs on the plunger. Once I
switched to a die cut it
came out perfect. I did some experimentation today with plastic up or
mylar up die cuts, and
plastic up seems to get a cleaner cut through the mylar, and bevels the
mylar edge downwards
towards the foam.
I also did some experiments time wise with putting old plastic and mylar
on new foam vs punching
20 at a time from a glued strip, and it is quite a bit faster punching the
later once a batch of
strips have been made.
I made probably 20 or so to replace a good portion of the keys in my Compaq
that had rotted aluminum. Surprisingly, the foam was still squishy; the
aluminum had just nearly vanished, presumably from moisture combined with
whatever is in the foam. I used the leather punch method and found that
they turned out very well. I didn't have much trouble with the bending of
the foam, perhaps because I was punching out of my three-layer sheet
material, which was wide enough not to have that issue. Anyways, the proof
is in the pudding, so to speak, as the keyboard is still working
flawlessly.
What plastic sheet material did you use? Like you mentioned, it does work
using the old plastic, but that is a lot more tedious.
Kyle