The Underwood undertakings continue…

The next step in this saga is to resurface the platen. The platen is the fat, round cylinder which the paper wraps around when you feed it into the typewriter. It’s also the impact-point of all those hammer-blows when you type. So its restoration is essential to the smooth running of the machine.

The exterior diameter of the platen and rubber is 45mm. 

The interior diameter of the platen, sans rubber, is 42mm. 

Therefore, the thickness of rubber required on the platen is 3mm. 

This is harder to achieve than you might imagine.

The first step is to remove the platen from the typewriter, explained in my previous posting on this topic.

Having removed the platen, it was then necessary to break off the old rubber. I did this quite effectively using a flathead screwdriver. I broke off the old glue which had crusted up around the edges of the platen, forced in the screwdriver-blade, and started jemmying away, levering the dried rubber up, and breaking it off as it came away from the cylinder underneath.

If you should intend to do this to your own machine, BE WARNED:

Early typewriters have platen cylinders cored with WOOD, not steel. Do NOT use anything overly sharp, that will gouge out or dig into the wood and cause it to crack or splinter. Otherwise you’re stuck doing even MORE work. That’s why I picked a blunt-point instrument like the screwdriver.

Resurfacing the Platen

To resurface the platen, you need fresh rubber tubing. If you’re lucky, you can find this at a hardware shop, a rubber-supply shop or other similar establishment.

However, specialty rubber like this is not as common in some places as once it was. Here, you must be creative.

There are two options available to most people:

1. Heat-Shrink Tubing. Easily purchased at electronic-supply shops and hardware stores, this stuff comes in a variety of widths, from a few milimeters, to several inches wide. If you have wide-diameter heat-shrink tubing on hand, buy some of that, along with the smaller sizes, to do both the platen, and the feed-rollers.

2. Bicycle Inner-Tubes. I wasn’t lucky enough to find extra-large heat-shrink tubing locally, and ordering it online was prohibitively expensive. However, there is another alternative. Not many people use and restore typewriters anymore, but fortunately for us, lots of people still go…cycling!

Every bicycle must have inner tubes which expand and hold air inside the tires. Nip down to your local bicycle-shop and ask about the largest-diameter tubing that they have available. This is a bit of a hit-and-miss affair, and it’s not nearly as neat and easy as using heat-shrink tubing, but it does work, and other restorers have gone down this path with success.

The tubes that you get need not be brand-new. If the shop is the kind that does in-house repairs for customers, chances are, they’ll have a whole bin or crate of used, punctured tubes lying around. Fish around in there until you find what you’re after.

Having found the right size/s (you may need more than one) of tubes, new or used, take them home and cut them open at the nozzle so that you have the longest length of tube available. Measure and cut the tube to the length of the platen. Also: Curl the tube inside-out. This will expose the SMOOTH inner-inner tube to the surface, which is better for the typewriter. Bicycle inner-tubes are filled with TALCUM POWDER to stop them sticking. You may have to dust or wash this off once the tube has been pulled over the platen.

Next comes the process of resurfacing the platen.

Having removed all the old rubber with care, ensure that the platen CORE or CYLINDER is free of imperfections and damage. Now, start layering heat-shrink or rubber tubing onto the platen.

If you have heat-shrink tubing, this should be much easier. If you have to do it with rubber tubing, it may be more fiddly and time-consuming, but it is possible. You may want to heat the rubber to expand it and make it more flexible while stretching it over the platen-core.

TIP: When removing the old rubber from your platen, keep the ends of the old rubber sheathing intact. This will serve as a guide about how thick to make the new platen-covering. 

An Interesting Observation

During my resheathing adventures involving the feed-rollers and the platen, I noticed that the shift and shift-lock mechanisms on the typewriter seemed to be malfunctioning.

I almost had a panic-attack! I didn’t come THIS far to screw up now! What happened!? What’d I do!?

The carriage kept jumping up and sticking in shift-lock mode, and I couldn’t figure out what was wrong. I decided to sleep on it and mull it over in the morning.

Taking a Holmesian approach, I examined all the evidence and analysed my movements, thinking about what I had done, changed or removed on the typewriter. I also examined the shift-mechanism itself to see how it operated.

As Holmes said: “Whatever remains, however improbable, must be the truth“.

The only truth I could think of was that I had removed the platen, and that, judging from the construction and operation of the shift-mechanism, the entire thing was weight-tensioned.

On a hunch, I dropped the platen-core back into the typewriter. Bingo!

As I suspected, the shift-mechanism works ONLY when the platen is in position. The added weight of the platen is what keeps the springs that operate the shift-mechanism in correct tension. Boy was that a relief!

Once the platen is fully resurfaced (it’s taking a while), another post will follow.