Saturday, May 25, 2024

C-key for the Remington Portable adding machine

The Remington Portable adding machine of the 1930s has a C-key protruding from the front. This C-key has a pointer to indicate the position of the next digit, pushing it to the right allows clearing an entered number from memory: marked C for Correction. These adding-listing machines can be branded Remington, Remington Rand, Monarch, Dalton, or Torpedo; and before the purchase by Remington of course Brennan. The C-key should all be identical, no matter what a particular machine is named.

(The C-key shown above is an original.)

The key itself is a press-fit onto a short stub of a stem. This stem slides into a pocket in the machine, attached to the machine's pin-bed memory. This key needs to be pulled-out to take off the machine's housing, it is only held in clamped by a spring. 

Being exposed on the front and also very easily pulled-out, these keys and/or stems are frequently missing from these adding machines.

A missing stem could be re-manufactured from a bit of mild-steel or brass of ~1.3 mm thick (probably 1/10th of an inch, but 1mm brass would also be fine). The tab that holds the key is bent 1 or 2 degrees up, tilting the top of the key slightly towards the operator. The V-shaped indents on the main ~11mm wide length that goes into the slot is where it is gripped by a spring. Below scan shows the overall shape of this stem with the main dimensions:

To replace a missing key itself, a CAD-model was made of this C-key's pointy-design:

With this 3D-model of the key and a good FDM-printer, this little pointy-key can be 3D-printed without any supports:

Printing with a small layer-height (0.1mm or less), the amount of visible layering is not too great. One or two layers of hobby-paint will mask any layering and will create a smooth, glossy key. The lettering then  picked out with white (or cream) latex paint.

(The C-key show above is a reproduction.)

Now the entry can be cleared again also on this 1930s Dalton-branded Remington Portable adding machine.

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