Measuring pivots

[gary17]

Hey

When you are measuring the thickness of a shaft pivot what part of the pivot is correct for jewel hole? 

Thickest part of the pivot? The tip? Or the middle? 

Cheers

Gary

[watchweasol]

Hi Gary  Middle to tip  that should be parallel, It rather depends on whether the shoulders of the  staff/pinion you are measuring conical or square shouldered.  the bit you are measuring is the working surface of the pinon.

[nickelsilver]

For pivots under 0.15mm-ish, especially balance pivots, you really don't want to use a micrometer. Even with a very soft touch you are almost sure to make a microscopic (or not so microscopic) pair of flat spots. For these it really is really important to use a jewel gage, which is a plate with jewel holes in increments from 0.07mm up to 0.25 or so, by 0.01 or 0.005 or 0.0025mm increments depending on the tool. Some will go down to 0.06mm (you really really don't want a mic on those little guys).

 

 

[gary17]

I was gonna use a jka feintaster. 

[nickelsilver]

7 minutes ago, gary17 said:

I was gonna use a jka feintaster. 

That should be ok. Just be careful not to tilt anything when the jaws are in contact, they can still leave marks.

[gary17]

Thanks.