Jewels: olive hole vs cylidrical hole?

[Orologi67]

ive read an olive holed jewel has less friction.  Is there a rhyme or reason to using olived holed ones as opposed to cylindrical holed ones.

When you replace, how can you tell its cylindrical as opposed to olive shaped?  You guys that work on watches constantly do you prefer to replace as many jewels that need replacing with olive shaped since they have less surface for friction?

Ive got a 3rd wheel that needs both jewels replaced.  Im thinking ill use a cylindrical one for the and olive shaped for the rest of the smaller train.

I have a microscope.  Can i tell the difference in whats already in the watch?  Will a cylindrical show a sharp edge and an olive show curve?

Thanks

Edited June 23, 2020 by Orologi67
misspelling

[CaptCalvin]

I'm not entirely sure what you're talking about, but I'm guessing you're talking about the jewels with a convex shape where it contacts the shoulders in the pivots so it contacts less of the shoulder's surface? If so I wouldn't stress over it too much. When under tension most of the pressure is on the sides of the pivots anyways. I wouldn't imagine the shoulders to contribute much friction when the train is under tension so I doubt it would make much of a difference. Although I would also imagine these to be more tolerant to more oil as they would discourage oil from seeping out past the shoulder. They are a feature of more premium watches. If you want them and can find them go for it. Otherwise leaving the other perfectly good working jewels in wouldn't be a bad idea.

 

EDIT: Just did some research. You're talking about the jewels where the walls in the hole are curved. I don't think I've ever seen these used or haven't paid enough attention to notice with the exception of the balance jewels. They would offer reduced friction but keep in mind less surface of the pivots are supported. As you get the same tension more focused in a smaller patch of the pivots you can accelerate wear. It also inhibits the jewels' ability to wick up the extra oil you would have on the pivot shoulders as the oil evaporates over the years which would also contribute to accelerated wear. I would keep these away from high tension areas.

Edited June 23, 2020 by CaptCalvin

[JGrainger]

The olive jewels are domed on one side, whereas the cylindrical jewels are flat on one side.

I suspect your watch uses cylindrical hole jewels on all wheel pivots except for the balance wheel. Olive hole jewels are sometimes used for the escape wheel when also fitted with cap jewels - this is pretty unusual in a watch though, most of those are also cylindrical.

[Orologi67]

Well i ordered all cylindrical jewels.  Had to order from otto frei and jules borel as one company didnt have all the jewels i needed.

This little LeCoultre table clock mustve been run a lot and never got serviced much.

There was much observed slop in all the pivot holes.

I bought it on ebay as not running.  The first thing i noticed apon taking it out of the shipping box was the minute hand was rubbing on the inside of the glass.  I thought that was stopping the movement.

Well no.  The mainspring had snapped.  I ordered the closest size MS I could.  Then i washed the movement such that i could proceed assessing other problems.

The second wheel had gotten bent when the MS snapped.  I noticed that when i went to polish the pivots.  Then i noticed the pivots were quite fuzzy.  So i smoothed those up.

Then i check for jewel erosion/loose pivot holes and there were a lot.

Im leaving the balance wheel for last.  I dont want to even look at that yet haha

Whoever owned it mustve kept winding it because it was stopping and or losing time.  Thats when whoever snapped the mainspring.

I think someone took it out to give the person an estimate to repair and when they put it back in the positioned the minute hand incorrectly

[JohnR725]

sometimes pictures help.

[nickelsilver]

As John's image illustrates, olive holed jewels can be convex or flat. Also, convex jewels exist that have straight holes. It can be tricky to see if a jewel is olive or straight holed, even with a microscope.

 

Generally speaking, flat faced jewels will have straight holes, convex jewels will have olive, unless labeled otherwise. Convex jewels are frequently encountered in higher grade watches with no cap jewel, the convex surface facing the shoulder of the pivot- like for pallet forks and escape wheels.

[JGrainger]

I'll have to keep more of a look out for those olive holes in future.. It's not presently the type of thing I'm usually likely to come across watch quality/necessary repair-wise.

[anilv]

It's all about reducing the contact area. Less contact area=less friction, which is what jewels are all about.

Anilv

[rodabod]

I’ve seen on some movements that the escapement jewels are modified with olive holes to reduce friction.  I tried looking at the holes with a quality microscope but it’s difficult to see the inner profile.