Jewel measurement and ordering sanity check

[mbwatch]

Hi all - I am working on a Langendorf pocket watch movement which needed the lower balance hole jewel replaced. This is my first time reaming, measuring, ordering a new jewel and I need to check with you experts if I made a mistake in ordering or if ofrei made an error in selecting the jewel they sent me. I did a load of research to prepare for this repair.

I reamed the hole up to a reamer measuring 1.19mm and my pivot measures 0.11mm. I ordered a convex olive hole balance jewel 12/120. I received the jewel in an envelope hand written 12/120.

When I went to press in my jewel, it fell straight through the hole with ease. I measured it with the most accurate equipment I have and I am getting 1.00mm.

So my novice question for you today is did I misunderstand the measurement and ordering or did the vendor send me the wrong diameter jewel at 100 instead of 120? Another way to ask this stupid question is should a 120 jewel order measure 120 or did I miss a detail?

[nevenbekriev]

No need to doubt, You have received the wrong stone. 120 is 120 and will allways measure 120 as out diameter.

What You did wrong is that You reamed the hole to 119, believing that this is the right way to fit new jewel there. Actually, the original jewel was rolled there and the hole and surrounding place has dedicated shape, and there often is no enough 'meat' to ream the hole and have normal walls as result, that will hold the pressed new type of stone right.  Often the decision is to ream enough so the surrounding of the hole is gone and make a bush that fits in this new hole, and the bush internal hole will take the stone. So now You can do just the same - ream more, fit bush in place and fit the stone in the bush.

[mbwatch]

3 hours ago, nevenbekriev said:

What You did wrong is that You reamed the hole to 119, believing that this is the right way to fit new jewel there.

Thank you for your confirmation! I am aware the original jewel was burnished in place and that those jewels are almost impossible to source today so I thought I would try pressing one in. The original hole was smaller than 120 (probably 100), and I have reamed out all of the original bush to fit the 120 jewel. Since this watch is for my own collection and not valuable I will attempt to press in a 120 jewel directly and if it cannot hold I'll eventually need to produce a new bush for it.

[nevenbekriev]

OK, sometimes it really happens without problems at all. You can take a covex oilve 120/12 stone from Molnija 3602.