Acquisition of Jewels/OD/Hole Diameter, Etc.

[SparkyLB]

I can measure the OD of a jewel if out of the mainplate with a JKA Feintaster, or appropriate micrometer.  I'm fairly sure there is a tool (is it called a pin gauge?) to measure the pivot hole size.   

What I can't seem to find info about is, what if need a certain size jewel (outside diameter) with a certain size hole?  Below are two educated guesses:  Am I on the right track?

1.  I'm thinking jewels are acquired that are a bit large and the mainplate is broached to an appropriate size for the jewel to be pressed and depthed?  (speaking of friction-fit; I'm aware that there are jewels contained in bushings that shoulder to mainplate--but I'm not referring to those.)

2.  As far as the pivot holes, I'm guessing that this is something that is not changed (unless using a lathe and micro drill bits?) and one sorts through many jewels until an appropriate size is found, then back to step one?

Finally, are jewels purchased in lots on eBay, or are they purchased by caliber/movement number?  I've looked on eBay for weeks.  There's no shortage of pallet entry and exit stones, but there is a distinct lack of round jewels for wheels.

Thank you all.  Forgive me if some terminology is incorrect.  I'm still somewhat a beginner.  

Edited December 27, 2019 by SparkyLB
brevity is the soul of wit.

[vinn3]

Quote

 

     the best tool for measuring a hole is a "ball micrometer".    you could make one via lathe.    i don't think one that small can be found.   vin

[watchweasol]

Hi   Regarding jewels they come in a lot of different sizes and as far as I am aware three types of setting, some are friction fitted using a seitz jeweling tool, some are in a brass setting and are screwed in and some are rubbed in. The rubbed in variety require special tools to remove broken or chipped jewels and a tool for rubbing in the new jewel into its setting.

There are assortments of jewels on ebay but it means sorting through and trying each one to find the correct fit, If you know the calibre and make and find the part number for the jewel then you are sure you get the correct size. The thing to do is to measure the pivot requiring the jewel then either order the same. Or if you are lucky enough to have phials of calibrated jewels select the correct size 

[Alaskamick]

You could buy drill bits from Cousins, they go from 0.5m to 2.00 mm.

These are jewellery drills but there are all types available, you would need to gently feed the drill through until you get to the shank witch will be the size of the hole.

Never having looked for jewels I'm not sure what the hole size would be.

[vinn3]

2 hours ago, Alaskamick said:

You could buy drill bits from Cousins, they go from 0.5m to 2.00 mm.

These are jewellery drills but there are all types available, you would need to gently feed the drill through until you get to the shank witch will be the size of the hole.

Never having looked for jewels I'm not sure what the hole size would be.

    twist  drills shanks can be sliped into the hole for an aproximate I. D..    vin

[SparkyLB]

3 hours ago, vinn3 said:

 

     the best tool for measuring a hole is a "ball micrometer".    you could make one via lathe.    i don't think one that small can be found.   vin

Thank you, vin.  I'll have a look at these implements.  I think I've seen spring loaded pin-type tools with a display not unlike a thermometer, and depending upon how deep the tapered pin enters the hole, the graduations on the stationary part tell the diameter.  

3 hours ago, watchweasol said:

Hi   Regarding jewels they come in a lot of different sizes and as far as I am aware three types of setting, some are friction fitted using a seitz jeweling tool, some are in a brass setting and are screwed in and some are rubbed in. The rubbed in variety require special tools to remove broken or chipped jewels and a tool for rubbing in the new jewel into its setting.

There are assortments of jewels on ebay but it means sorting through and trying each one to find the correct fit, If you know the calibre and make and find the part number for the jewel then you are sure you get the correct size. The thing to do is to measure the pivot requiring the jewel then either order the same. Or if you are lucky enough to have phials of calibrated jewels select the correct size 

Thank you, watchweasol.  You answered the question regarding can jewels be ordered by part number, i.e. calibre.   

3 hours ago, Alaskamick said:

You could buy drill bits from Cousins, they go from 0.5m to 2.00 mm.

These are jewellery drills but there are all types available, you would need to gently feed the drill through until you get to the shank witch will be the size of the hole.

Never having looked for jewels I'm not sure what the hole size would be.

Thank you for the resource, Alaskamick.  I'll get some of these for sure.  I'm guessing they ain't cheap!

11 minutes ago, vinn3 said:

    twist  drills shanks can be sliped into the hole for an aproximate I. D..    vin

Absolutely.  

 

Thank you all for replying.  I'm putting back together a very old orphaned movement, and the jewel hole for the 3rd wheel (not a seconds wheel in this case) is badly broken, preventing the train of wheels to be driven; at least downstream of the center wheel.