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                Hints and Tips --- Polishing Clock Pivots

  Before showing how to polish the pivots, I thought that it would be a good idea to explain why you must use a pivot file and not some other kind! A pivot file has been designed for the sole purpose of dressing hard tool steel pivots. The teeth are of extremely fine cut and the file is much thicker than any other of its size. The file will not bend when in use and the edge is offset so you can get right into the root of the pivot. I have heard of people using a needle file for this job but I doubt that they will have had much success.  

After a while the file will become clogged with steel dust,-sweat,-oil etc, and must be cleaned. 
The best way is to use a piece of 1/8" thick brass plate and push along the grain of the file.
The brass will soon take on the cut of the file and remove all of the unwanted gunge.

There are lots of ways to do pivot polishing and I will try to give an insight into the ones that I know or have used.
The traditional tool used is called a Jacot tool. This is a disc of metal, tool steel, brass, bronze etc and has a series of half holes or runners on it's outer edge, used for supporting the pivot being worked on. The Jacot tool in the pictures was made some 18 years ago and fits onto the cross slide of the lathe. The traditional tool was designed to fit into the tailstock of the lathe and has a crank arm which carries the disc. On my small lathe I found that I was restricted in certain setups using a tailstock setup as the clock wheels would foul the cross slide.  I said that it is the traditional one but by no means the only one.  

Another way is to make runners from brass rod or steel. An 18" inch length of 1/4" diameter brass rod will cover most common clock pivots and give some spares left over for specials.

Cut the runners into 1 inch lengths and place in the 3 jaw chuck of the lathe, face each end flat. Drill a hole the same size as the pivot and long enough for the pivot you are working on. File the rod to half it's thickness and you have made your first runner! To make a set for future use you can start with a drill size of, -8mm then 1mm, 1-2mm etc up to about 2-6mm.

For the larger arbors, e.g.- fusee and Longcase barrel, you have to use your imagination and ,or whatever tools you have in the workshop! You could of course make a Jacot tool for these larger items.  

Another way is to dress the pivots by hand methods.

Hold the arbor in a pin chuck and support the pivot on a block of wood which has a shallow groove filed into it.

Rotate the pin chuck towards you and at the same time push the pivot file over the pivot, it sounds hard to do, but with practice it becomes, quite easy. In fact some strike lever arbors would be nearly impossible to do, any other way.

Using this same technique you can make your own taper pins from steel or brass wire. Sometimes when using the Jacot tool, especially on the larger clock arbors, Longcase or fusee for example. The pivot has a tendency to (pick up) while burnishing. This looks like a smear of metal around the pivot and can only be got rid of by using the hand burnishing technique on a block of wood.

There are certain situations which will dictate the setup you have to use but all I can say is NEVER be tempted to use the opposite pivot as the driver while polishing as it will surely end in tears. There again, I could always write an article on re-pivoting!  

The basics. The top 3 are pivot files, the one underneath is a combined pivot file and burnisher. The lower 2 are burnishers.

 

2 Cleaning a file. Please note that this is an ordinary bench file and not a pivot file. The lower portion of the file has been cleaned with a piece of scrap brass.

3 Forming a cross grain onto the burnisher using coarse (120 grit) abrasive cloth.

4 A lantern clock pivot before polishing

   

5 The same pivot after polishing.

6 The other end of the arbor, being polished in the Jacot tool.

7 Typical setup using a Jacot tool.

 

8 This picture shows a common situation in clock repair. How do you hold the right hand end of the arbor in the lathe while polishing the other pivot! The arbor is short and tapered and will not hold in the lathe chuck or a collet. Easy

   

9 Make a simple carrier from whatever you have in your junk box, or adapt other tools for the job. The hollow tool steel tube, was made for riveting pinions onto clock wheels, but I have used it as a carrier in this situation.

10 The short portion of arbor sits in the tapered end of the tube. The crank arm locates onto one of the wheel crossings and drives the wheel .

 

11 With all these setups you have to provide support to the arbor before starting the lathe. If you don't, the arbor, wheel assembly will most probably be damaged. Some repairers place the pivot file onto the pivot before starting up, but I like to have the luxury of taking the file away to inspect the pivot while the lathe is still going. For many years I have used a piece of wood with a notch in the end to hold the arbor onto the runner. You don't have to press down hard, just firm.

12 Fusee arbor repair. The bearing surface had worn below the original arbor diameter. This picture shows that the arbor diameter had to be reduced to provide a new bearing surface. Please note this setup is only possible if the winding square is not bent!

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13 The same fusee pivot after polishing.

 An article on bushing clock plates-- CLICK HERE

  A tip on making your own movement holder for clocks under test -- CLICK HERE

HOW TO MAKE A CLOCK WHEEL HOLDING DEVICE - -CLICK HERE 

 

 

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