Burnishing, how do I do it??

[berntd]

Hello,

I am just starting out and I would like to burnish some pinions on a clock I am working on. My books do not really give nnough details on how to do make a burnisher and how to use it properly.

I have ruined one pivot already due to my lack of knowledge.

Can anyone please let me know how to make a burnosher or show picture of how a burnisher should look like?
Must it be used with a special paste or something to work?

I had no sucess with using the rear smooth part of a needle file.
The grooves just became deeper on the pivot.
I also tried 3000 grid emery paper on the file with no real luck.
Lastly I tried the file itself and that ruined the pivot almost immediately by rounding its shoulder and by making it cone shaped .

I have now stopped all further operations until I can get some better information.

Kind regards
Bernt

 

[Charles E. Davis]

Bernt
I have had good success in my clock classes for many years doing the pivot polishing on an adaptation of the old fashioned Swiss and English Turns made by from a large door hinge. There are several threads over the years but this one does a pretty good job of describing what is involved.

https://mb.nawcc.org/showthread.php?t=18707&highlight=Pivot+Polisher

 

[Hayson]

Check out the following sites for excellent descriptions of traditional burnishing methods by expert practitioners:

http://www.abouttime-clockmaking.com/downloads.shtml

http://home.att.net/~jclosch/articles.htm#pivots

 

[berntd]

Hello all and thank you for the links.

I have read those and I did actually make a jacot tool with brass disks etc as decribed here:

http://www.davewestclocks.co.uk/making_a_jacot_tool.htm

It took forever to make nicely but the result is great.
I am now using this tool with my lathe so I hopefully will not need the hand burnishing tool made from a hinge, although it is a great idea and very tempting.

The problem I have is with the acual burnisher and method.
Somewhere along the line, I am missing the piont as it is written that burninshing does not remove metal but then on the other hand, my books also show pictures of "metal to be removed by burnishing or pivot filing"

Then they mention left and right hand tools but why would I need those and why are they different? How does it all differ from filing?

The burnisher has lines sanded into it across? Why? To hold a paste or compound perhaps?

I know what I need to aim for on the actual pivot but I don't know how to get there. :bang:


Kind regards
Bernt

 

[LaBounty]

Hi Bernt-

Burnishing is a stretching and hardening of the metal. It is common for some metal to be removed during the process but the amount is minimal and true burnishing won't significantly reduce the diameter of the pivot like polishing will.

"Pivot filing" should be considered a polishing process while "burnishing" is a hardening process.

As far as the difference between right-hand and left-hand burnishers goes, page 7 of the first article has the following on right-vs-left hand burnishers...

"A right-hand burnisher will allow the clockmaker to burnish the pivot from underneath
with the piece being held and rotated from their left. A left-hand burnisher will allow
burnishing from underneath while being held on the right."

The burnisher is relieved on one side so you can burnish right up to the shoulder. You will need to select a burnisher which has the relieved side towards the shoulder. Right or left will depend on which method of holding the work and tool you prefer.

Page 10 of the "Burnishing" article has the following...

"In order for the burnisher to properly burnish a pivot, it must have a surface which will grab and stretch the steel of the pivot. The surface must also be flat and free of pits or other defects. If the surface of the burnisher develops any defects as a result of use, it must be re-prepped..."

The lines which are sanded or ground in the surface of the burnisher make it a very fine file which will stretch the steel and harden it. No paste or compound is used in the burnishing process other than an oil lubricant. Paste or compounds are frequently used in the polishing process but must be thoroughly removed or they will contaminate the fresh clock oil.

ClockClass.com has a DVD available called "Pivot Finish" which shows the process. (The DVDs are not region specific.)

Hope that helps and keep the questions coming!