New spacebar for an Oliver 3 typewriter

The ends of the spacebar of an older Oliver typewriter are often broken off. The spacebar is made of a 'plastic' material and the ends are relatively thin and exposed. Not surprising then that the spacebar on this battered Oliver 3 was broken at both ends. Makes the machine look as if someone gnawed on it.

Only the thicker section between the pillars remains; and like the rest of the machine was slathered with black paint. And gnawed at both ends.

From the remaining 'stub' and pictures online of Oliver's that still have an intact spacebar, the dimensions were estimated and a 3D model was made. Included are pockets for the stop-buffer and threaded holes for the pillars.

This model (available on Thingiverse) was 3D printed in PLA (strong!) and painted. Unsure what the variations in color originally were; in pictures they vary between almost black to a mid-brown. This reproduction anyways painted brown (and waxed for good measure). Likely will be re-painted in a darker shade later, for now it'll do.

The pockets underneath are the buffers for the bottom-stops; originally these probably were leather. In this reproduction spacebar, rubber disks of 8 mm diameter by 2 mm thick are a press-fit. Disks of leather, furniture-felt or even simply card would also work. (Hole-punches are relatively costly, but a full set of hole-punches from 1 to 25 mm is one of the best investments in tools I ever made! These get a surprising amount of use.)

Mounted on the Oliver 3 it makes the machine looks more 'whole'. It also looks perhaps a bit too new and out of place on the battered black machine (a re-paint in olive-green may yet happen).

American National 14-20 screw thread and 7/8th Inch

The rubber 'stopper' feet of Underwood 5 typewriters are almost always 'gone'. The rubber is generally hard and the weight of the machine has compressed the foot. This is bad, not just because the rubber does not dampen any noise anymore, but also because it means the machine probably now rests on a sharp metal 'pin' on the head of the bolt that is inside the rubber 'stopper'. So; best replace with new feet.

To make new feet for an Underwood 5; a simple plastic cylinder was made to take original, salvaged bolts taken from disintegrated Underwood 5 feet. These could have been 3D-printed in rubber (TPU), but in this case printed from rigid PLA and given a pocket to take 3 or 4 mm stick-on furniture felt. The felt was given a rubber-coating for anti-slip.

These foot-bolt inserts are turned from square stock and have a ~6.15 mm threaded stud for mounting on the machine. Re-using these bolts is a good thing, because this is today an uncommon screw-thread. It's almost the same as UNC 1/4" with 20 tpi, but not quite. With tolerances of manufacture, a modern quarter-inch UNC screw may fit the machine, but it's about 0.2 mm too wide. (Outer diameter of UNC 1/4" is 0.250" (obviously) and #14 diameter is 0.242".)

An Underwood 5 has American N 14-20 threaded holes for mounting the feet; this thread was removed from ASME standards already in the 1940s. This used to be a fairly common screw size as I've read. To add to the diversity of threads, it exists both as 14-20 and 14-24 (i.e. 24 threads per inch). In either case, today nearly unobtainable. 

So it's a good thing to re-use the original bolt-inserts of the old, original feet if possible.

Sizing of the feet themselves is a guess - estimating from the remains of the old feet, chose a diameter of 20 mm (25/32 inch ?). On photographic evidence of the 1920s the feet do look similarly thin and cylindrical, but not quite as thin as all that.

Giving it some thought, a diameter of 7/8" is more likely. As we're 'anoraking' anyways and these being easily printed; manufactured a new set with the larger 7/8" diameter.

These look a bit more substantial - and less ridiculously flimsy on the machine. Now the Underwood 5 typewriter with new cylindrical feet that are probably similar to the original when-new feet. 

It remains to be seen how well these feet hold up over the years. The PLA material is very strong at room-temperatures, but will weaken when hot. At temperatures over 60 degrees C they will probably slowly 'collapse' and be squished (actually, just like the original feet did! Very authentic :-). That's where the felt-pads come in, they will prevent the bolts from protruding and scratching the table.

For now, this common Underwood is on a stable footing again. And with the cushioning felt, also much quieter on the table! :)