Got 2 questions for the hairspring challenged!!

1 - Looking for the formula........
As you know the pinning point at the collet should be oriented properly with the position of the watch itself.
When you vibrate a spring, you first find the appropriate spring by sticking it to the staff with a bit of rodico (at least this method works for me!!).... test the spring to see if it's going to give you the right beat... then take it off, break out enough of the center to fit the collet, and install the collet temporarily.
Then you vibrate the spring to find the position of the beat point - where the reg. pins should end up... and then a little further out on the spring the stud pinning point.
THAT point, when in the watch, is fixed... it governs the rotation of the spring, and the collet, and the pinning point at the collet, and there's no reason why it should automatically put the pinning point in the right orientation.
SO the dilemma.
You can see where the collet pinning point is, but you see that it has to rotate say 100 degrees in order to be in the right orientation. Obviously you can break more spring off and rotate it, and re-pin it.... But how much do
you add at the stud end to get back to the proper BPH?
That's what the math is for.
You can also re-vibrate it... you know the spring will have to be made longer so you just grip down the line somewhere and figure it out.

2 - One I've never been able to figure out is where to start raising the overcoil once the pinning points are known...
AND since the overcoiling causes the body of the spring to rotate... it will also cause the collet
to rotate...
So how do you compensate for that when you pin the collet?
Surely this doesn't have to be a guessing game!!

Paul

This whole subject is something that you really need to be taught on a one to one basis as the written explanations are far to lengthy I dont realy have the time to do this.

Basically once you have pinned the collet and found the vibration point (where the regulator pins will sit centrally) you need to correct the error angle between the two.
If
A = number of degrees from regulator pins to the line drawn from the center of the collet tangentially through the exit of the collet hairspring in the same direct of hairspring coil direction.

Then from the formula below “B” equals the number of degrees to remove form the collet pinning point.

(A+A/3) - 60 =B

Paul,

maybe this drawing from the TM9-1575 helps you....

http://i4.photobucket.com/albums/y106/LIGE00/breguetspirale018.jpg

rgds

Enzo

Hi Paul,

1. its easy: you have to add the same length of hairspring outside, that you took away inside. Math would be overkill, you can estimate it with your eye.
With math: the ratio of outside angle (unknown) to inside angle (your 100°) equals the ratio of inside diameter to outside diameter.

2. The additional angle, that the 'regulation point' will move, is usually given in the Breguet tables. Do you use tables??
The overcoil starts roughly 180° before the regulation point on the not yet bent hairspring. The two raising knees are directly before that start and are not part of the overcoil.

You can also draw the hairspring and overcoil magnified on a sheet of drawing paper, and compare the length of unbent hs. vs. overcoil with a thin thread to find the terminal angle.

BTW. you were talking of the collet pinning point for pocketwatch (1st half turn over the horizontal line),
Chris was talking of pinning point angle for wristwatch, that maybe confusing.

Regards,
Frank

Gentlemen,

Thank You to each and every one that responded with the excellent, thought provoking answers!

After an "extended" weekend (I considered it almost "un-citizen" to ignore the holiday, and even take an extra day off - you can do that when you are in your own business!!)I took each input and "tested" the thoughts on my own.
And guess what??!!
All proved correct in their intended scenerio.
Yes, it is a 16sz HS I am working with.
And to have everything explained so easily.....again, Thank You so very much!!

Have A Great Day!!

Paul

sounds like the hairsprings delicate and inportant? Soo it shouldnt be hammered back to flat and held with pliers? haha yust kidding.