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I recently received a Royal "Model O" Portable from 1937. The machine was taken with a good bit of rust, and when inspecting I found the U, N, and 7 key wouldn't budge, which I learned is because the slots the slugs are fitted into are rusted on the inside. This is the case for almost every slot of the keys. I've been trying to flush it out with alcohol, but after a cleaning it just goes back to its previous sluggishness. What should I do to get this rust out most effectively?
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Alcohol won't do it -- it doesn't remove rust. There's stuff called PB B'laster (I think I am spelling it right; never used it myself) that does remove rust. Naval jelly is another type of product that removes rust, but that stuff may be too strong.
You could also try something that actually scrapes the rust off but that doesn't remove the metal, since the typebars (the levers that hold the slugs) are supposed to have no side to side play in the slots. I'd suggest trying a toothpick -- softer than the steel of the slots but might be hard enough to rub the rust off. If that doesn't work, then using some very fine emery paper, and gently so as to not widen the slots, would be my next approach.
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Hi Teran
In a situation like this, your best friend is probably a good penetrating oil like PB Blaster (as Fleetwing mentioned), Kroil, Seafoam's Deep Creep or liquid wrench to get between the sides of the slots and the type bars to soften the rust so the type bars can be gently moved back and forth. One of the regular members frequently uses transmission fluid to loosen rusted and seized parts. I've also hears it said that a 50/50 solution of transmission fluid and acetone will get right into the thickest rust and get things moving.
Once the type bars start moving, apply occasional shots of oil to wash the rust away. Once all the type bars are moving freely, wash the oil out with solvent, camp stove fuel or isopropyl alcohol, then continue with a thorough cleaning of the entire mechanism.
Note, WD-40 was never designed as a penetrating oil and is not as efficient as purpose formulated penetrating fluids and tends to leave a sticky residue which will come back to haunt you later. Hope this points you in the right direction,
Sky