Monday, August 8, 2016

Jeweled Escapements

Addendum: One of my readers, Adam, sent me an eBay listing of an encased escapement from one of these and it is clear that there also is at least one jeweled bearing on which the escapement wheel rotates.  It is possible that the dogs mentioned below are not jeweled, but to my eye they still appear to have tips which are not steel.  It is most likely that just as in a watch several parts are jeweled.
It is my mission now to find one of these in horrible shape which I can tear apart so we can have more definitive information.  I am somewhat considering tearing apart my own Classic 10, but it's probably still in good enough shape I shouldn't.

Surely some of you have seen this symbol on some Smith Corona typewriters, this example being an early sixties Classic 10.  You have probably wondered what a jeweled escapement is.  Maybe you have seen watches labeled as being 7, 15, 17, or 21 jewels.  The jewels used are often corundum (gem varieties being ruby and sapphire) and they are used either as bearings or in places where they are struck to reduce wear and friction.  Corundum has a hardness of  9 on the Mohs scale, just below diamonds which are hardest. 
The escapement in a typewriter works like an escapement in a watch.  There is a gear with long curved teeth which can be sort of seen in the very center of this photograph.  Each tooth is a space.  Sometimes if one tooth is missing or damaged a machine might skip every certain number spaces, that number being the total number of teeth on the escapement gear.   The movement of this gear is restricted by little escapement dogs, and those are the parts which are jeweled.  In the picture below we zoom in roughly to the red box seen here.
Here we have one of the teeth on the escapement gear indicated by a blue arrow.  The two dogs are both indicated with green arrows.  If you look closely at the tips of these you can see they are a different color, sort of a black in contrast to the steel.  These are the jewels.  If you google "Pallet Stone Jewels" in regard to watchmaking you can probably find a pretty clear diagram.  Since they are a blackish color my guess is that these would be sapphires, but obviously not ones which are gemstone quality.  They are however, indeed literally jewels.


  1. Well, shiver me timbers. didn't know there were actual jewels in there. :D

  2. This post is a real gem. Thank you for illuminating it!

  3. I remember wondering about this a few years back. Thanks for the illustrations!

  4. Ah so, grasshopper! So it's actually jeweled escapement DOGS! Most illuminating, thanks for the post and the pics.

  5. Interesting, I didn't really know much about the jewelled escapement either. :)

  6. Interessting Details. Sadly, one SC Silent Super I bought recently is missing the left of the jeweled Dogs + clip. I conntacted the seller in hope he still has it somewhere. If he doesn´t I can just try to recreate one. If someone has any Ideas for that I would be very thankful! :-)

  7. I recently aquired one of these jeweled escapement sc typewriters and found this information, the typewriter is in excellent condition, is this possibly of any value?

    1. It depends entirely on which typewriter it is... but probably somewhere between $25-50 USD.