[TheForge] switchplate

Fri Jan 9 18:10:01 2004

Really nice George, not that I'm surprised.

Switch and outlet plates have been on my drawing board since I started
building the house but the precision necessary has put them on a back burner
till I get the shop up and some proper tooling made.

This is exactly the kind of project where doing it all by hand can put you
behind the curve. You already use all kinds of dies to mass produce
elements, textures and such, why not use dies to do the tedious precision
work as well? It'll require a higher degree of precision than spring dies
can but it's well within the range of alignment pins.

We used this type of die in Father's shop to punch and stamp precision parts
by the thousands daily. I'm not suggesting you try stamping the entire part
of course, just the screw and switch holes in the blank.

Here's how we made them. The bottom or reciever plate is of high carbon,
high impact tool steel. Father's shop was a full blown production shop and
tooling had to last for hundreds of thousands of parts at least. In a more
hand work oriented operation, good high carbon steel should last plenty
long. The top or tool plate was medium carbon steel to minimize deflection
but didn't need to be as wear resistant as the reciever plate nor punch
dies.

The top and bottom plates are matched and aligned by pins. The pins slide in
holes in the reciever plate and are attached solidly to the top plate. The
reciever plate has holes to recieve the desired punch(s), in this case two
for the screw holes and one for the switch. These hardened tool steel
punches are of course attached to the top plate and are precicely aligned
with the holes in the reciever plate.

To prevent distortion of the blank part in the die we had a third (I'll call
it the "sandwiched" plate as I don't recall the names for most of these
things anymore <sigh>) matching steel plate and a piece of hard rubber sheet
attached to the top plate. As the die closes, the first thing to make
contact is the sandwiched plate, the press (or treadle hammer, etc.) drives
the top plate down, compressing the rubber, extending the punches into and
through the blank part.When the press, hammer, etc. retracts heavy springs
raise the top plate, the rubber rebounds and pulls the punches back through
the sandwiched plate and the part drops free without jamming.

Punching all three of these holes in one shot under a treadle hammer would
be a real feat eh? It sure would, even hot. Punching multiple holes was
beyond the capacity of the punch presses in Father's shop too, so I'm going
to let you in on what was 40+ years ago a trade secret that let Father's
shop compete with far better equipped shops than ours.

The punches didn't make contact at the same time, they were all slightly
different lengths so the press was actually only punching one or two holes
at a time. The two screw holes can go at once but the large rectangular
switch hole would be a bear all by itself, possibly impossible in a single
shot under a treadle hammer.

If however, the rectangular switch punch is ground at an angle so it first
makes contact at one corner then progresses through the blank like a shear
rather than a punch, it'll go fine. It's not a sharp angle though or it'll
distort the blank, the difference between first contact and final punch
through is only 2-3 x the material thickness.

Frosty
------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

----- Original Message -----
From: "George Dixon" <[email protected]>
To: <[email protected]>
Sent: Friday, January 09, 2004 5:45 AM
Subject: [TheForge] switchplate

> Greetings,
> Here is a prototype that I did yesterday .........
> http://www.artist-blacksmith.org/switchplate.jpg
> It is made from 16g sheet metal with a coal-forged texture, linseed oil
> finish followed with paste wax.
> It is amazing how much precision is required to mate 25 cents worth of
> sheet metal to a 79 cent switch......
> George Dixon
> abana member
>
>
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