Garryflex for polishing pivots

Phil G4SPZ

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Garryflex is a rubber compound impregnated with silicon carbide abrasive particles. The Museum, where I work as a volunteer horologist, use it for cleaning rust etc from cast iron and other artefacts, and they gave me a piece of the 240-grit material. A finer 320-grit version is available too.

I have recently been using it to polish clock pivots, where the arbor is rotated slowly in the lathe (or by hand) and the soft Garryflex block is gently pressed onto the pivot. I then push the pivot into some pithwood.

It works a treat and is less risky than burnishing, particularly with fine pivots found in 400-day clocks. Obviously this process won’t restore badly damaged pivots but definitely improves the surface finish of undamaged pivots. It will also impart a shine to and remove tarnish from steel arbors.

74C751D3-314F-4231-9F88-CE5F9260E2FA.jpeg

Phil
 

wefalck

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I have been using a product called arc-o made by a (German) company Artiflex. Seems to be similar. Very useful indeed to clean metal parts without significantly altering their shape.
 
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Phil G4SPZ

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Hi Mike, and hello again to you, Eberhard! I hope you’re both well.

I recall back in my childhood that you could buy a hard, abrasive rubber that was designed to clean rust and tarnish off the surface of the rails of model railway layouts, to improve electrical contact with the locomotive wheels, a problem well known to all railway modellers... I now recognise that product must have been Garryflex, or something like it.

I only mentioned its efficacy in polishing pivots because I’d never seen it discussed in clock circles before.

Phil
 
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D.th.munroe

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They are quite handy, Cratex is another similar rubberized abrasive.
People have suggested that one for pivots, I think Butterworth even sells the 1/8 rotary tool wheels of it for that.
Dan

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karlmansson

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Good tip!

Then of course there is the age old question of form and function in pivots. Abrading and polishing will make them pretty and run better for a while but will not create the same wear resistance as burnishing will.

I need to get somthing like Garryflex for finishing larger larts though. Seems to leave a nice finish!

Regards
Karl
 

wefalck

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Karl is right, Burnishing with a steel burnisher not only polishes and smoothes the surface, but makes it actually denser - it is not an abrasive process.

Using Cratex, Artifex or whatever the brand name may be, rubber abrasive wheel does not lead to a geometrically well-defined surface. So I am not using it on any bearing surfaces.
 
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Phil G4SPZ

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I absolutely agree that burnishing serves a totally different purpose, and an abrasive will not restore a pivot where wear or damage is present. That’s not what I use Garryflex for; it’s just quicker and more effective than pithwood alone and improves the surface finish.

Phil
 

D.th.munroe

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Cratex may be harder then, it would be quite hard to push a pivot into this suff.
My friend used to use a pen eraser for that, they were grey and white or pink and blue, and very cheap.
 

measuretwice

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Karl is right, Burnishing with a steel burnisher not only polishes and smoothes the surface, but makes it actually denser - it is not an abrasive process.
Not sure I buy that it increases density but it does burnish and I agree with your conclusion. Its also, partially through burnishing and partially through material removal is going to impart flatness, i.e. a straight cylinder. A soft abrasive will not which I think is one of the objectives.

Material removal with a burnishers is very slight. Use some oil, burnish and inspect a drop of the oil. You'll see only the slightest hint of grey in it from the steel removed. I would estimate that the Cratex products I use for various things, in the various grits, would remove material at a much higher rate, perhaps magnitudes higher, than burnishing

Keep in mind, there isn't one level of burnisher. You can tune (or make) them to different levels. e.g. one made from a coarse stone will have more action than one prepared with a fine stone, etc. A fine one will hardly remove any manterial
 

wefalck

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My understanding of 'burnishing' as a process is that surface roughness and surface geometry are smoothed out by 'forming' not by abrasion. This means that high points in the surface are displaced by pressure into lower areas (microscopically speaking), rather than cutting them away with an abrasive compound. This is why a hardened steel or carbide burnisher is used, that has been ground very flat as well. This displacement effect I meant to describe by 'increasing the density'.
 

measuretwice

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My understanding of 'burnishing' as a process is that surface roughness and surface geometry are smoothed out by 'forming' not by abrasion. This means that high points in the surface are displaced by pressure into lower areas (microscopically speaking), rather than cutting them away with an abrasive compound. This is why a hardened steel or carbide burnisher is used, that has been ground very flat as well. This displacement effect I meant to describe by 'increasing the density'.
agreed. The burnisher although also cuts ever so slightly. Much less than the abrasive imo. SOP with a burnisher is that they are stoned so the lines run perpendicular to the axis, much like the teeth on a file. The micro burrs created by this do have a cutting action, which of course will be more or less depending on the coarseness of stone used on them. We're talking small stuff here, but the lines are there on a burnisher and they do (and are supposed to) remove a small bit of metal. After much use, you can freshen up a burnisher by stoning it again

I've got a Hauser power burnisher that uses a carbide wheel. Its, as far as I can tell, perfectly smooth. Its action must be exactly as you describe with seemingly no cutting action. But for the handheld long thin ones we all use, I believe they burnish and also do the tiniest bit of cutting (the "chips" are just barely apparent in the oil)
 
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D.th.munroe

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You can prove to yourself that burnishing work hardens a fine skin on the pivot, with a lathe and a graver, cut a pivot in some good steel, burnish it well, then try to cut some more from it.
 
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karlmansson

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I Always get a gray haze on my burnisher when I burnish pivots. So I Think I'm removing a Little bit of material. I'm also not sure if burnishing actually increases the density of the steel but I would like to learn. I am however positive that is does work harden the Surface and creates a very wear resistant and slick skin.

This is a pretty comprehensive study on the matter of finishes. Does not adress hardness though: http://abc.eznettools.net/D304430/X353088/Pivots.pdf
 
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wefalck

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I am not a watchmaker, but understood that work-hardining is part of the objective of burnishing pivots.
 

MARK A. BUTTERWORTH

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We carry a series Of three discs, course, medium, and fine to go with the mandrels mentioned.. The disks are impregnated with carbide and work extremely well.
 

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