Burnishing Pivots - Important? - Do you do it?

[chezwilly]

After reading all of the popular clock repair books, especially those geared towards beginners, I noticed an almost complete lack of mention about burnishing pivots. All the books touted the importance of polishing pivots but almost nothing about burnishing

The questions are: Do you consider burnishing pivots an important part of clock repair? And, do you do it

Thank you.

Willy

 

[MARK A. BUTTERWORTH]

I believe the critical factor is to polish the pivot to a mirror polish. Burnishing is a waste. Just my opinion.

 

[Charles E. Davis]

Burnishing soft pivots along with bushing are the two most important aspects of clock repair for American style clocks.
In all of the years I have taught clock repair (since early 80's) I have taught new students to do this with simple equipment that they can easily construct with hand tools.
I show lots of pictures and deal with the construction in several threads. This is one of the more extensive ones.

https://mb.nawcc.org/showthread.php?18707-Pivot-polisher

 

[Charles E. Davis]

I believe the critical factor is to polish the pivot to a mirror polish. Burnishing is a waste. Just my opinion.

I have a little trouble with talking about burnishing and polishing on the same pivot.
Polishing is done with abrasives and is the only method that will prepare a hard steel pivot. If the pivot cannot be "cut" with a file, abrasives are your only option and a burnisher is useless at any stage.
If you are working with soft steel pivot like most American style clocks using the file/burnisher is the only safe way to prepare pivots. Abrasives run the risk of embedding in the pivot and cause damage to the bearing surface.

 

[shutterbug]

I do polish and burnish the pivots, but note that many American clock manufacturers (if not all) DIDN'T. There has also been many discussions on burnishing bushings. I don't.

 

[Charles E. Davis]

I do polish and burnish the pivots, but note that many American clock manufacturers (if not all) DIDN'T. There has also been many discussions on burnishing bushings. I don't.

I'm sorry that my mention of the importance of restoring pivots and installing bushing implied burnishing bushings. I do recommend using cutting and smoothing broaches when doing bushing. A cutting broach will size and upright the hole. The smoothing broach does what its name says. Smooth any ridges and move metal to form a uniform surface with the dream of a hardened surface through rubbing under pressure.
As far as pivots when they left the factory, all of the repairer's efforts are directed in restoring a "just like new" surface to the pivot through burnishing /or/ polishing.

 

[shutterbug]

I've seen machine marks on pivots that were more than likely from the factory. So 'just like new' is often better than new

 

[chezwilly]

Thank you guys. As always knowledgeable responses. Your help and advice is greatly appreciated. I especially liked Charlie Davis's hinge.

Willy

 

[bangster]

My comment, which will satisfy nobody:

When pivots need filed, I also burnish them. But more and more I'm filing less and less, and polishing with graded abrasive buffs instead. Yoda

 

[Scottie-TX]

I'm a polisher. Tried burnishing - I think it's overrated. But Steve Nelson has provided some thought provoking evidence of the value of burnishing in long duration Viennas with supporting data showing measured improvements in performance after burnishing.

 

[leeinv66]

I'm also a polisher. I wouldn't say burnishing is overrated, but in many cases I think it is unnecessary.

 

[Bruce Alexander]

I'm a polisher. Tried burnishing - I think it's overrated. But Steve Nelson has provided some thought provoking evidence of the value of burnishing in long duration Viennas with supporting data showing measured improvements in performance after burnishing.

I started out working with popsicle sticks of abrasive paper, grits running from 320 to 2000 followed by sticks impregnated with Tripoli and Rouge. I've been working more with stones and burnishers as per Steve Nelson. My technique is kind of a hybrid now because I use both, especially since I don't have, nor have I ever used, pivot files.

 

[doug sinclair]

If you are dealing with a modern clock with nickel plated arbors and pivots, and the plating on the pivots has started to peel, and the bearings are badly worn, there are a number of options. Replace the movement, replace the wheel and arbor, and bearing, or repair the damaged pivot, and re-bush. If the third option is chosen, the plating must be removed, and the pivot trimmed and polished. If this is the chosen option, I think it is imperative to burnish the pivot because of the soft steel alloy. Un-plated, hard steel pivots should only require a trim and polish if they are a bit rough or worn.

 

[Scottie-TX]

Again TAT; No surprise we agree.

especially since I don't have, nor have I ever used, pivot files.

I do have them but they will last forever because I regard their use ONLY for heavily pitted, rutted, soft pivots common to less expensive clocks with soft steel pivots and I certainly would never waste my time burnishing these.

 

[R. Croswell]

The questions are: Do you consider burnishing pivots an important part of clock repair? And, do you do it

Very interesting questions when put this way. I mostly work on American clocks with soft pivots and until I see documentation otherwise I tend to believe that these pivots probably were never burnished at the factory therefore burnishing them as part of a restoration would not seem to be a requirement. However I agree that the intended outcome of burnishing is desirable. I usually polish and carefully clean pivots. I have burnished pivots but I am usually not pleased with the result and I'm sure it is my lack of mastery of the technique rather than the technique itself that is to blame.

I'll throw in a few more thoughts. first, I believe a good polish job beats a poor or mediocre burnish. Second, I suspect there are some who apply a burnisher to a pivot and say they burnish pivots without ever achieving the benefits that are theoretically possible if done correctly. And third, The question posed is only an indication of who uses or prefers which method and perhaps the percent of responders who use that method. It does not establish which method is superior. A large number of users of one method does not establish that method as the best method.

RC