Friday, September 22, 2023

Replacing a pin with an M2 screw on the Mignon index typewriter

To take apart the actuator arm of a Mignon index typewriter, a soft-steel pin has to be removed from the hollow main actuator rod. This 2mm pin holds the 'plug' with the ball-on-a-needle that is the vertical type-alignment bearing. Only when that is removed, can the parts be taken apart further; the actuator arm in bits:

This pin is in an awkward position. Pins are unpleasant to remove anyways, but this pin is very close to the delicate casting of the arm-assembly. Any stray hammer-tap on that part and it would shatter for sure. 

Also the horizontal bearing-tube is concerning; this also seems to be a fragile Zamac casting. Over time the material can swell and the part will then be very hard to slide out of the cast-iron forked-lever. On this machine only filing down of the centre-section was needed to get it out.

Putting it all together again, the needle-plug was fixed in the actuator-rod not with the pin, but with an M2 screw and nut. 

The brass M2 screw is a very tight fit (scraping), leaving no play between the parts. (Any play would introduce vertical type-alignment variation.) This screw is not authentic, but is normally not visible from the outside. More importantly; an M2 screw won't need hammering close to fragile Zamac castings and will make future repairs so much easier.

Also the soft pin that locks the horizontal-rod (right-end) was replaced with an M2 screw. The M2 nut is an exact fit in the slot of the horizontal-rod, making it an easy replacement. Again not authentic, but not very noticeable and much easier for future servicing. (Well, if there ever would be any, of course).

Most index typewriters were low-cost flimsy affairs, but the Mignon actually has a heavy cast-iron frame and is overall solidly-built.

It does have far fewer parts than a standard typewriter (and was about a third of the price), but it does have a similar build-quality. (Just wish that they hadn't used Zamac and pins!)

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