The term "COA" is generally meant to refer to the "C"leaning, "O"iling, and "A"djusting of a timekeeping device such as a clock or watch. In the narrower view of the Pocket watch, my topic about Grace the 8 year old watch maker is a pictorial of what we generally refer to as the "COA" of a watch, at least to a single position/temperature. That means we check the timing in a common position (pendant up) and adjust the Mean Time screws until it has least error in that position. Then we quickly check to see that it does not deviate too much in the other positions which would usually mean that there is a pivot problem. For the watch to be truly RR accurate is by no means accomplished this way.

To make watches RR accurate, (30 seconds error per week rather than 30 seconds to a minute per day) there are some good references to how to "fine tune" for;

"beat" by rotating the balance spring collet;

"positions" by "tweaking" the balance (hair) spring and pressing in and out the movement jewels to control train wheel endplay;

Temperature by moving about the weights on the balance wheel;

BUT little is said (or usually done) to address the POISE of the balance wheel that is REQUIRED for ANY watch to actually be "adjusted" because the books PRESUME the Balance wheel has been poised (balanced) already on a good poising tool (see pic).

It's simple: "POISE" is essential to all of the above factors because if the balance wheel wants to swing one way (with reference to gravity) more than the other then it will go "every which way but loose" depending on what position the watch is in regarding the direction of gravity acting upon the watch!

SO! SIMPLE RULE; If you want a watch truly adjusted to positions when it is serviced by a (good) watchmaker INSIST that the balance wheel is poised FIRST, and then the watch adjusted.

This sounds simple but it requires cleaning ALL the debris and hubris from the balance wheel and then poising the wheel without moving the mean time screws. That takes a GOOD poising fixture, and someone who knows how to do that in the hour or two it might add to correctly adjust the watch.

THIS IS WHY MOST ALL RR GRADE WATCHES CAN HARDLY BE EXPECTED TO ACTUALLY RUN ACCURATELY NOW, THEY ARE NOT IN "POISE"!

So when some of us who suffer dry perspiration working on our watches "gloat" about the accuracy of a certain watch, it must mean that we "went there" to risk the "life and limb" of the watch by pulling off the balance spring and poising it.

One extra note; if you ask Chris (for example) to make your watch "super accurate" be prepared for his charge of a few more hours work to get it there.

David,

all the above sounds like Ludwig Van 5th to my hears !!!
tnks rgds


Enzo

David,
Thank you again for your very informative posts.
Just what do you do when you poise a balance wheel? How?

Ed, Chris will have some more to say wbout this I am sure, but the following is basically what I do. It is somewhat different than the factory where they had a near infinite variety of graduated balance weights to juggle around and quickly bring the wheel into poise. . . .

To poise the Balance wheel as a service action;

1. Gently pry up by it's collet the balance (hair) spring assembly and and set it aside. (mark the stud position to the rim of the balance wheel first with a slight "nick" to the rim of the Balance wheel.)

2. Carefully check that the Roller pin (jewel) is securely attached to the roller.

3. Very Carefully Clean the Balance wheel assembly.

4. level the poising tool and set the spacing between the parallels so the straight pivot ends of the Balance wheel staff are what is touching the parallels.

5. Puff on the wheel to start it "rolling" along the parallels.

6.
a. If it is in balance it will stop randomly.
b. If it is not in balance it will rock back and forth around a "heavy" side of the wheel.

7. Either lighten the heavy side balance screws, or add 1 minute balance washers to the light side of the wheel and recheck for proper balance.

8. Continue doing step 7 until the wheel is "in poise" (balanced).

9. Replace the Balance spring assembly making sure the stud is properly relocated with reference to the registration mark you made on the wheel.

You will probably have to re-time the watch and also "tweak" the balance spring collet around some to bring it back into "beat" again, but when you are finished it will be more "positions accurate" than before.

Well you have touched on a huge subject here and a good opportunity to indicate that as I think Dave was trying to show that there is a far cry form a simple clean to what should be addressed in a service. I will attempt to skim over a few points I would really need to spend a lot of one to one time discussing the whys and wherefores in the reasoning behind the detection and rectification.
We will assume that the rest of the watch is in good order and look solely at poising a balance. The first thing I do before poising the balance is identify the errors and know beforehand roughly how much timing errors you maybe looking at from the outset and possible causes, this is in itself affected by many other adjustments and I consider just to be one of many factors that will affect my approach. As far as I know they leave the factory reasonably poised the modern watch are near perfect or should I say perfect when made, it is years of abuse that throw them out people changing staffs, twisting and bending things tampering randomly with screws, corrosion, contaminates, badly fitted rollers, pivots bent to name a few.

What we are trying to achieve is that you can place the balance on the poising tool, set true to the tool and with the pivot face only resting on the jewel edge. Using a small puffer or single hair from a brush rotate the balance to ANY position and stop without the wheel showing any signs of corrective motion or falling to a heavy point. One myth is that being able to roll the wheel from one end to another is a sign of a good wheel, it proves nothing to poise as the speed will overcome small errors but can help detect a bent pivot.

The first thing you need to do is to spend a good deal of time looking and seeing what has gone on in the past to cause the error, remove the hairspring very carefully I do not mark the position as you can nearly always find it is incorrect position from the outset and finding a start position is easy. if you disturb the coils especially near the collet where you are using the removing tool unless you know how to correct these the watch will NEVER keep time, I made a small tool that allow me to unscrew the hairspring off the staff and avoid the possibility of marring the arms of balance more important on wrist watches as pocket watches are normally well chewed up from years of abuse. Once down to the bare balance and roller, I normally examine the shellac and if old, missing or badly applied I we clean off and take the opportunity to replace it only take a minute to do and worth while as this will also affect the poise if done at a later time.
They using your best loupe examine the weights (we are assuming we have a typical balance from a pocket watch and we assume that the mean time screws if any are as new set evenly and no one has messed with them in the 100 years+, I had a Dent PW yesterday that someone had filed a wedge off the head on the meantime screw to poise the watch)
Look carefully to see if timing washer have been fitted and also if they are mirrored on the other side of the balance, indicating if they where there for poise or timing adjustment, look for screws badly filed off, undercut/drilled and chewed up, are the screw all the same size and same position on each side, same color. It is these type of indications that will tell you if you are dealing with a scrap watch made ready for ebay, sometime you will find that the watch has been messed with so much it is beyond practical repair v cost, this no doubt send them back onto ebay.
Next you need to really check the pivots if they are slightly bent you cannot poise your wheel, sometime you can place it on the poising tool and roll along slowly using a high magnification you can see the pivot wobble, also a good time to burnish your pivots in the jacot tool if needed or if any doubt simply replace the staff. Then you need to check that the wheel is true using your calipers and make good any errors.

Well time is pressing and will have to leave it here for now, but you get the general idea to start.

Dave and Chris,
Thank you very much for taking the time to answer a novice's questions. I am begining to understand the complexity of these marvelous little machines.
When I first started to collect pw's it was like collecting coins. Which one's were the most desirable to collect? Which were the more scarce, etc? The more I learn here on IHC185 about what makes them tick/run has taken precedence in my interests of these little machines.
Again, thank both of you for providing a valuable service to the novice's that frequent IHC185.