Question about replacement stems for Unitas 6497

Discussion in 'European & Other Pocket Watches' started by James_B, Mar 26, 2020.

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  1. James_B

    James_B Registered User

    May 11, 2018
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    Hello all. Has anyone ordered and used any of those Chinese replacement stems (direct from China on Ebay) for the vintage Unitas 6497 movements? If so, have you found them to fit well? That is, are they nice and tight or is there slop to them?

    All things being equal, I’d like to purchase a new stem from Esslinger (preferred since I'm in the US) or Orfrei; but, not only is Esslinger apparently out of the specific stem they say I need, by the time you add in shipping from either of those businesses, the cost is anywhere from half to three-quarters of the cost of an entire Chinese clone movement. So, I’m wanting to go inexpensive.

    Regards,
    James
     
  2. Rick Hufnagel

    Rick Hufnagel Just Rick!
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    Oct 25, 2018
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    James, have not had a problem with the Chinese stems. They work perfectly fine. Have used a few of them. Not sloppy and fit well.
     
  3. James_B

    James_B Registered User

    May 11, 2018
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    Thank you, Rick. I will give the Chinese stem a try.

    ** Longer explanation for those who like to read and look at pictures **

    I was concerned about the Chinese stems because a pocket watch I just bought has a stem profile that looks very much, if not exactly, like the Chinese ones. It’s boogered and I need a new one. A previous owner apparently tried to cobble together a stem/crown, and the crown didn’t originally fit, so he glued the crown on or something, because the threads at the top are caked with a substance I can’t identify and I’m not sure how to remove.

    I found conflicting information regarding the stem size of Unitas/ETA 6497s. I’ve seen both tap 7 and tap 10 listed as the thread size. However, tap size seems to be the only size ever referenced when it comes to measuring stems. The 6497 (open faced) and 6498 (hunter configuration) movements, both apparently use the same stem (according to Esslinger at least). I happen to have both a 6497 (the newly acquired PW) and a vintage 6498 movement, so I, of course, pulled out the stem of my 6498 to compare the two. To my surprise, they are not actually the same size. I drew a picture of the stem profiles and put up the caliper numbers I measured on each piece.

    Based on the two stems I happen to have, it looks like 7 is the real tap size. But as you can see, the diameter of the various corresponding parts of the stem are anything but exactly the same. The stem from the 6497 is smaller in every profile but the thread tap. My biggest concern centers around the square shank.

    So, I stuck the 6498 (“bigger”) stem in the 6497. It fits apparently as good or better than the original. Now, I should mention that it seems both stems actually fit. They can wind the watch and set the time; however, my concern is that the smaller original stem’s slop will eventually wear the sliding pinion, rounding the square hole and destroying the part.

    Looking at the two stems, the Chinese ones listed online look pretty much exactly like the “smaller” one that came in the 6497 movement, so I’m worried that the tolerances are “slightly” too big. If the Chinese stem is the same dimensions as the smaller one I already have, is a 0.07mm difference too small a difference to really be concerned about?

    Anyway, I’m now going to buy the Chinese stems and make a comparison. I have no idea if this is enlightening to anyone, but I hope you enjoy.

    Regards, James

    IMG_2782_Web.jpg IMG_2776_web.jpg
     
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