Dial Indicator Repair using minature ball bearings

[measuretwice]

An indicator repair.

I call this watch-like work in that its similar tools and techniques so thought some might find it of interest

I have this Helios tenths dial indicator that needed some help.  It was locked up, so, with some bergeoning (haha misspelled double entendre?) watchmakers skills I decided to have go at it.   Helios (German) stuff imo is of excellent quality and well worth restoring

 

 

On disassembly I found that several jewels were cracked. 

 

 

First task is to remove the chatons from the plate.  Here, everything has been cleaned.  I usually keep simple green degreaser solution in the ultrasonic cleaner and after removing most stuff run it through the L&R for a final clean.  The L&R with the right solutions does an amazing job.

 

 

Here’s a close up of a cracked jewel.

 

https://i.imgur.com/SFnXyau.jpg[/img]

 

The breakthrough on this repair was the discovery of inexpensive miniature ball bearings.  New jewels are available, but after shipping the cost of the three needed would exceed the value of the indicator (used anyway).  So it and a few similar projects sat until I recently read a 2011 Horological Times article by Mark Butterworth, “Reducing Friction in Clock Bearings and Bushings.  There are precedents to this in horology (Hermle, Sattler) so I thought to give it a try - an indicator has a much easier life than a clock (based on duty cycle) so if it works in a clock maybe it will work here

 

Better still, there are seemingly good quality low cost miniature bearings available now, in the range of 2 for buck!

 

Here’s a shot of the 3 x 1 mm ball bearings I used, with a typical watch jewel and razor knife blade included for size comparison.  I think I bought a bag of 50 from that online retailed that used to be a great auction site 

 

 

I set up a lathe to make new chatons to fit the plate and bearing and went into production.   I have several indicators to look at as well as a travel so thought it worthwhile setting up a turret.  It was good experience, I made some tooling for the turret and ended up disassembling the turret and fixing a few things…so I partially justify the time as the shop the got better 

https://i.imgur.com/jtNF3jK.jpg[/img]

 

 

 

As a second op, I used a watchmakers lathe to clean up the other end.  I snipped off the burr, gently countersunk the bore and filed a slight bevel (with a fine watchmaker’s file) on the OD to help start the press fit

 

Back with the staking tool, the chatons are pressed in

 

 

Pressing in the bearings is really delicate.  Too much of a press and you’ll damage the bearings.  Also use a stake that only puts pressure on the outer race.  In making the chatons I bevel them so they could be rubbed in but ended up with a nice press that held them but didn’t damage them

 

https://i.imgur.com/ymQUbqT.jpg[/img]

 

I discovered what I thought was a depth issue as there was some binding of the wheels.  I pressed the chatons a little further in and things ran smoothly.  It turns out I hadn’t pressed the bearing to the bottom on the chaton, but at the time thought I must have made an error in their length

 

With this erroneous conclusion, and the chatons now proud of the other side, I needed to face off the now pressed further in chatons.  ( didn’t discover it was the bearing press depth until later) These watchmaker lathe faceplates make such a job just so easy to do.  With a very accurate centre through faceplate’s collet mount, work is easily centred

 

 

 

 

I used rodico in the bearing to keep it clean – it really did the job and caught all the swarf.

 

https://i.imgur.com/Jg6Z3vg.jpg[/img]

 

The pivots that go into the 1mm bores don’t need any attention but any going into plane bearings got  inspected and polished

 

 

Cleaned, here’s the completed indicator working to perfection.  3 jewels needed replacing. 

 

 

 

[nickelsilver]

That's a nicely done job! Personally I'm not a fan of ball bearings in sensitive lightly loaded areas. I've seen it be a problem in several watch designs (think micro ball bearings and escapement parts). The problem is what I call the "skateboard effect"; I'm sure most folks have seen a kid go flying off a skateboard after hitting a tiny pebble, the little wheels get stopped instantly.

In a ball bearing proportionally small balls with even smaller contact area take the load of an axle that is relatively large. The big upside is a corresponding reduction of friction. The downside is the smallest imperfection can have the reverse effect, not too much so in heavily loaded bearings (like a great wheel in a clock) or fast spinning situations (like ball bearing equipped yo-yos), but in very lightly loaded areas like a watch escapement or a sensitive indicator a microscopic contaminant can either stop it dead or have a heavy influence on resulting performance.

All that said I don't want to sound critical of the work- I think your indicator should work fine, the tension spring probably has enough oumph to get through if it's functioning smoothly and is clean inside now.

[measuretwice]

Thanks....Indicators are imo more forgiving than a watch, really more like a travel clock than a watch, i.e. more robust.  (I have a similar repair planned for a travel clock).  They also have a strong return spring and almost an insignificant duty cycle in comparison.  One thing is to run the bearings dry, minimal friction. You're never wear them out and with no  oil there's glue to hold contaminants in place.  I corresponded with Mark Butterworth on this and his view was they will last longer than a plane bearing in a clocks, which I also see as far more demanding environment (because of duty cycle) than an indicator

Edited September 26, 2019 by measuretwice