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Best Stock for Making Balance Staff


jdrichard

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20 hours ago, measuretwice said:

Marc,  what sort of material allowance for burnishing would typically shoot for?

It's a bit of a "how long is a piece of string" question as it depends on a number of variables.

I like to try and get to within 0.05mm to 0.1mm if I can before moving to the Jacot barrel/runner on my turns (I don't have a dedicated Jacot tool) although that can be a real challenge for me on the smaller pivots. I then use a pivot file to reduce it further before finishing off with the burnisher (my pivot files are double sided; file one side burnisher the other). The sort of factors that determine just how close you can get on the lathe are;

Target pivot size; the bigger it is the easier it is to get really close to it without risk of breaking the pivot.

How sharp your graver is; the sharper the better.

How quickly your pivot file cuts; you don't really want to be spending hours on the Jacot if you can get a bit closer on the lathe.

The quality of your stock material.

Your technique on both the lathe and the Jacot.

 

As OH said it's something that comes with experience and varies from person to person. What I would say is that even with a big pivot, a supremely sharp graver, top quality stock, and no coffee in the system, I would still leave enough fat on the pivot to burnish to size for the work hardening effect on the pivot surface.

 

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It's a bit of a "how long is a piece of string" question as it depends on a number of variables.
I like to try and get to within 0.05mm to 0.1mm if I can before moving to the Jacot barrel/runner on my turns (I don't have a dedicated Jacot tool) although that can be a real challenge for me on the smaller pivots. I then use a pivot file to reduce it further before finishing off with the burnisher (my pivot files are double sided; file one side burnisher the other). The sort of factors that determine just how close you can get on the lathe are;
Target pivot size; the bigger it is the easier it is to get really close to it without risk of breaking the pivot.
How sharp your graver is; the sharper the better.
How quickly your pivot file cuts; you don't really want to be spending hours on the Jacot if you can get a bit closer on the lathe.
The quality of your stock material.
Your technique on both the lathe and the Jacot.
 
As OH said it's something that comes with experience and varies from person to person. What I would say is that even with a big pivot, a supremely sharp graver, top quality stock, and no coffee in the system, I would still leave enough fat on the pivot to burnish to size for the work hardening effect on the pivot surface.
 

No coffee was the best advice


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Industrial supply houses, such as MSC, sell drill rod. It is stocked in hundreds of different diameters. The most popular types of steel are  "O" (oil hardening), "W" (water hardening), and "A" (air hardening). The water hardening rod is the least expensive and is generally used in applications where deformation due to heat treating is not an issue. Ironically this is the most common steel for watch staffs. This is probably due to the choice of material available at the time watches were first made and succeeding watch makers stayed with the tradition. Oil hardening rod is generally used for end mill cutters, reamers, drill bits etc. and cost more than the water hardening steel. Air hardening steel has the least amount of deformation, is the easiest to heat treat,  and is the most expensive. It is used in applications where size and geometric deformation is a critical issue such as stamping dies. Of the three types I listed any of them can be and are used to make watch staffs.

david

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The prehardened and tempered "blue steel" from watch supply  houses is generally water hardening tool steel. The cost for a 6 foot length of the unhardened material in a similar diameter is only a few dollars. Six feet should be more than a lifetime supply for most watchmakers.

david

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The prehardened and tempered "blue steel" from watch supply  houses is generally water hardening tool steel. The cost for a 6 foot length of the unhardened material in a similar diameter is only a few dollars. Six feet should be more than a lifetime supply for most watchmakers.
david

Where is the best supply house for this material?


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JDRICHARD,
I buy mine from MSC but there are a bunch of others such as TRAVERS, McMaster Carr etc.. Drill rod is also sold on Ebay.
david

There is a company locally that sells drill rod. W0 is what i think would do. 1/8 inch may be the smallest.


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Drill rod can be a few different chemistries...O1, W1 etc.  My preference is O1.  whatever, but make sure you know what you're getting or you won't be able to heat treat it properly.   Where is local?  if you're in TO I'll give you piece of 1/8 O1.  Any industrial supply should have it and for sure any metal service centre - eg Metalsupermarkets, KBC, and so on

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4 hours ago, szbalogh said:

A drill rod should be ok as is. It is made to be strong and hard :) hence no need for heat treatment. But reacquires tungsten gravers for sure. 

I agree it is a lot tougher than regular old mild steel, but imo still needs heat treating
(which is not difficult and doesn't need complicated equipment).   When you buy it, its annealed, easily cut with hss tooling or for that matter carbon steel tooling.  Its tensile strength shoots up from around 90,000 psi annealed to 280,000 psi hardened and tempered, so heat treating will have a big impact on how it performs and wears.

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6 minutes ago, measuretwice said:

I agree it is a lot tougher than regular old mild steel, but imo still needs heat treating
(which is not difficult and doesn't need complicated equipment).   When you buy it, its annealed, easily cut with hss tooling or for that matter carbon steel tooling.  Its tensile strength shoots up from around 90,000 psi annealed to 280,000 psi hardened and tempered, so heat treating will have a big impact on how it performs and wears.

Ah, sorry i meant the ready to use drill bit, and not the toolsteel. I have bought 2mm drill bits and just cut off the helix part and turn from the rest. 

On the other hand the hardening is not so tricky as i understand. It has to heated up and quenched in cold brine to get it really hard as old staffs. 

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yeah the chucking end of drills are not hardened, and if they're hss you wouldn't be able to heat treat them.  The ends are left soft so the chuck can get a grip on them.  This one reason why you're not suppose to use an endmill in a drill chuck - its hardened all the way along itself can easily spin in a drill chuck because the jaws get no bite.

One has to select the quench to match the steel.  W1 is a water quench, O1 is oil etc.  The differences are the speed of the quench - you'll get O1 in oil about the same rockwell as you will W1 in water.  Oil is slower than water, cold brine fastest of all.   O1 in water is too fast and you risk cracks.  W1 in oil is too slow, you want get full hardness.    Don't forget to temper though!

Of the different tool steels, ie if not buying pre done blue temper stuff, I'd recommend a length O1 oil hardening tool steel (aka drill rod but not all drill rod is O1!).  Traditionally a little more expensive that W1, the quench is a little slower than for W1.  A couple of bucks for a three foot length of 1/8" diameter will last a looooong time and its easy to machine as it comes annealed so is also good for practice :)

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