Pivot file

[binman]

Why are pivot files handed, is it to do with the pivot /arbor shoulder. I found one amongst some taps I brought that is marked left hand, I believe I use this on my left hand side held under the pivot.

 

[gmorse]

Hi binman,



The one on the left is a "left-hand" pivot burnisher, and you can guess what the right-hand one is! So if used under the pivot rather than over it, you can see why they're named that way. Does yours have one edge rounded?

Regards,

Graham

 

[eskmill]

A good pivot file has a smooth, slightly angled edge that when placed against the pivot shoulder of the arbor does not act against the thrust surface of the shoulder when properly handled. The opposite edge is a right angle and when bearing against the arbor shoulder would tend to turn-up or roll-up a rough edge on the thrust surface of the arbor.

Pivot files are useful only on soft, mild unhardened steel arbor pivots such as found on inexpensively produced timepieces or on some older cottage-craft antique movements.

It is not unusual that some mass produced clocks have steel arbors which were case-hardened or metal coated so as to produce a thin but hard, wear-resistant microscopic surface. Such arbor pivots, when subjected to accumulated grit, eventually loose the outer coating or hard surface due to abrasion and the exposed softer or milder steel beneath is easily reshaped using a pivot file and or burnishing.

 

[Steven Thornberry]

I have moved this to the Horological Tools forum, where it might get better exposure and where it properly belongs.

 

[binman]

Hi Graham, what I have I think is a pivot file but the sides are square. It is smooth one end and slightly rough the other. The case is a round stainless steel case, it serves as a handle, there are two half round pieces of wood that slide into the case to hold it still, on the case are the words Gauche. On the file one side is a Fish with the word Suisse on the other are three words G.antgihe,glaroon,and vallorre. Don't no what they mean it's 178mmx 6.55 x 3.20mm

 

[gmorse]

Hi binman,

I think your file is marked "G.ANTOINE" "GLARDON" "VALLORBE", (the maker's name and location in Switzerland), and on the other side a "G" for Gauche, (left) with the fish trademark and "SUISSE" , which is exactly what one of mine has. If you look at it end-on, you'll see that the section is a parallelogram rather than a rectangle, and is used under the pivot when it's pointing to your left, or over it when it's pointing right, as it normally would be with the headstock on your left.

Regards,

Graham

 

[Max Phillips]

It was mentioned earlier that pivot files are only used on soft steel but I wanted to clarify that this isn't really true. A pivot file will work great even on pivots made of properly spring tempered steel. I rarely use mine on soft steel, as it's typically hardened and tempered steel that I'm turning pivots from.

 

[shutterbug]

It is specifically for "over" or "under" pivot polishing/burnishing. I find the under method most helpful for watching what's happening to the pivot surface.

 

[binman]

Thank you all for explaining everything for me, the other question I have is if using a lathe what is the best speed to use I assume about 300rpm.

 

[binman]

Bump

 

[Max Phillips]

Thank you all for explaining everything for me, the other question I have is if using a lathe what is the best speed to use I assume about 300rpm.

It would all depend on the diameter of the part you're working on. The appropriate RPM would be calculated based on a desired surface speed and the diameter of the part. 300 is way to slow for anything most people would use a pivot file on (however I use my pivot file for lots of things that most people would not).

This page has some good info that might be useful to you - they recommend 4 to 5 times the speed you'd use for "rough turning", with ferrous metals: http://www.smithy.com/machining-handbook/chapter-3/page/32

You can tell when the speed is too high, the file will no longer feel like it is cutting.

 

[binman]

Thank you Max.

 

[glenhead]

According to David LaBounty's phenomenal treatise on burnishing (http://www.nawcc-index.net/Articles/LaBounty-Burnishing.pdf‎), start slow and light and end fast and hard.

Glen

 

[Max Phillips]

According to David LaBounty's phenomenal treatise on burnishing (http://www.nawcc-index.net/Articles/LaBounty-Burnishing.pdf‎), start slow and light and end fast and hard.

Glen

I can't access that document, but I can't imagine a pivot file being involved in burnishing, unless the author is discussing preparation of the pivot before actually burnishing it.

 

[gmorse]

I can't access that document...

Try here.

 

[Max Phillips]

Try here.

Thanks! That's a great article but I see no mention of filing.