Pocket Watch Bench Key Dimensions

Discussion in 'Horological Tools' started by piedmontg, Nov 4, 2019.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. piedmontg

    piedmontg Registered User

    Jun 14, 2009
    11
    1
    3
    Hi

    Just starting to learn how to take apart and put together a pocket watch - and have it still running. I am collecting some tools and thought I could make a set of mainspring let down keys - however.

    I searched this site and found threads that gave sizes but they were different, some overlap. Did a Google and found another set of sizes.

    I see them for sale but they look easy enough to make, I can easily make a square, and harden / temper if necessary. I like making my own tooling.

    Is there a source for the sizes? or are they just sort of close enough.

    Here are the numbers I found (all mm):
    .6 , .7, .75, .9, 1.15, 1.4

    .7, .8, .95, 1, 1.2, 1.3, 1.4, 1.45

    .6, .8, 1, 1.1, 1.3, 1.5

    I mic'd two different 16s cases and got 1.13, for an 18s it was 1.26.

    One could argue the ones above are all the same, as they are within .05 mm in general ( ie about .002") but I make parts that have to fit better than that to run.

    I would like to at least start by knowing what is what. Maybe what I will find with experience is that I need a varied set and which ever one fits - well use it.

    Thanks
    Bob
     
  2. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,263
    20
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    Hi Bob;
    Sorry you haven't any replies yet, but I went and measured the ones I have, which I believe were Elgin. The sizes I have are:
    .75, .88, .97, 1.08, 1.16, and 1.31. These are of course all in mm. I haven't had a watch yet wherein I needed to make one because I didn't have the size I needed in these. Hope this helps!..............................gary
     
  3. piedmontg

    piedmontg Registered User

    Jun 14, 2009
    11
    1
    3
    Gary

    Thanks for the information, I think I will make up a set, or see if I can find some on line. Last set of three I saw went for $75.
    Bob
     
  4. Clocks In The Grove

    Clocks In The Grove Registered User
    NAWCC Member

    Dec 3, 2011
    79
    7
    8
    Male
    Oregon
    Country Flag:
    Region Flag:
    I am not a watch guy so I am not sure what a pocket watch bench key is. I see that Timesavers sells watch keys (2.00-0.95mm) for $1.50 each. The small sizes above must be something different. Could someone post a picture of what is wanted?
    ..Bob..
     
  5. roughbarked

    roughbarked Registered User

    Dec 2, 2016
    3,483
    209
    63
    watchmaker
    Western NSW or just this side of the black stump.
    Country Flag:
    Region Flag:
    Keys may also be male rather than female. One can grind engraving drill burr shafts with male squares to fit various American watches.
     
  6. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,263
    20
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    #6 doc_fields, Nov 7, 2019
    Last edited: Nov 7, 2019
    Here's a picture of what I was describing to Bob. Sorry for the lousy picture quality, but it's early...........................

    Benchkeyspwletdown.jpg

    Generally, bench keys are for letting down pocket watch mainsprings, AND for winding them up when the movement is outside of it's case. It takes the place of the crown and stem which usually remains in the case. I have never had a female ended bench key come across my bench, but rather all have been male ended. The pocket watch keys in Timesavers catalogue, page 64, are replacements for lost keys, not as bench tools per se. I have used those keys as let-downs, but usually for Swiss Lepine movements where the key directly winds the mainspring through the back of the watch. I made a holder for the keys using a clock suspension spring post that is slotted. But I hardly ever use it. I'll post a picture of it in my next post...............................gary
     
  7. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,263
    20
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    #7 doc_fields, Nov 7, 2019
    Last edited: Nov 7, 2019
    Here's this homemade letdown using the Timesaver watch keys. I don't like using these keys for this purpose, as the hole in the end is inset , and sometimes doesn't fully engage the male end of the mainspring barrel. That end has to be turned down a bit in the lathe or filed to prevent that.......................gary

    watchkeyletdown.jpg
     
  8. Clocks In The Grove

    Clocks In The Grove Registered User
    NAWCC Member

    Dec 3, 2011
    79
    7
    8
    Male
    Oregon
    Country Flag:
    Region Flag:
    Thank you Roughbarked and Doc-Field for the reply's. Always something to learn. So it looks like parts suppliers(like Timesavers) do not carry these tools. As small as the tools are, one would want to have good steel and not something that rounds over. Thanks again.
    ..Bob..
     
  9. roughbarked

    roughbarked Registered User

    Dec 2, 2016
    3,483
    209
    63
    watchmaker
    Western NSW or just this side of the black stump.
    Country Flag:
    Region Flag:
    Engraving burrs are hard enough and if perchance you get the steel hot enough to lose the temper, it is not difficult to retemper.
     

Share This Page