If you’ve been trying watch regulation on vintage watches for any length of time and you’re not getting the results that you would like, this video is going to start building the base of knowledge.

In order to be consistently successful at regulating watch movements, you as the watchmaker need to first understand the relationship between the hairspring and the regulator pins.

So, grab a notepad and let’s dive into one of the most complex subjects in watch repair.

Watch Regulation: The Basics

Most new watchmakers are under the impression that regulating a watch is just a matter of moving the regulator arm towards the plus or minus symbols.  That’s because that’s all they’ve ever seen, or they’ve had some minor success doing that.

There will be instances where that’s all you need to do. But in vintage watch repair, that’s almost never the case. So, let’s start off with the flat hairspring.

The Flat Hairspring

For a watch to keep accurate time, the hairspring needs to be the correct length. It also must be the right weight for the frequency that the movement was designed to run at.

Frequency is also known as beats per hour or BPH for short.

To find the correct length of a hairspring, a watchmaker uses a vibrating tool. Inside the vibrating tool, there is a balance wheel and a hairspring of a known value that acts as a control.

Balance Wheel on Vibrating Tool
Balance Wheel on Vibrating Tool

The balance wheel inside this tool is set up for a movement running at a frequency of 18,000 beats per hour.

The end of the hairspring is held by a clip. The hairspring and the balance wheel are suspended with the balance pivots resting on the glass directly above the control balance inside the tool.

Hairspring and Balance Wheel vibrating affect watch regulation
Hairspring and Balance Wheel

Vibrating the Hairspring for Watch Regulation

The spot on the hairspring that is held by this clamp is known as the counting spot. Remember this because you’re going to be hearing it a lot. The two sets of balance wheels are set in a motion so that they rotate at the same time.

The point where the hairspring is held by the clip is slowly shortened until both balance wheels are synchronized together. We want them so they are rotating in unison at the same speed.

When this is achieved, the point on the hairspring that’s held by the clamp is known as the real counting spot.

The Real Counting Spot

This is the sweet spot on the hairspring. Theoretically at this spot the rate should be very close to zero.

If the counting spot was moved to make the hairspring longer the rate would lose time. If the counting spot was moved in the other direction to make the hairspring shorter the rate would gain time.

Shorter hairspring equals slower rates, shorter hairsprings equal faster rates.

Counting Spot one the Regulator Curve

When we install the balance into a working movement the real counting spot needs to be located on the terminal curve near the middle of that curve. This ensures that there’s room on either side of it for adjustability.

The other thing that happens is the real counting spot changes its location on the terminal curve. Why it does this is a complicated subject but let me try to just summarize it for you.

Why the Counting Spots Location Moves

You may have noticed that when a hairspring is oscillating in and out it does not wind and unwind concentrically. In other words, the spacing between the coils are not exactly equal on opposite sides of the hairspring.

This is actually a natural fault of the hairspring. It is caused by the pinning point where the hairspring bends and goes into the collet.

Collet Pinning Point
Collet Pinning Point

When there is a really tight bend, it changes the center of gravity of the hairspring. This is why the hairspring appears to be slightly offset as it breathes in and out.

Hairspring Offset When Oscillating
Hairspring Offset When Oscillating

Practical Counting Spot in Watch Regulation

This offset condition wasn’t present when the hairspring was originally being vibrated.

When it’s in the movement and running flat, the real counting spot on the hairspring changes position. This is because of its relationship to the hairspring’s pinning point of the collet.

Practical Counting Spot affects on Watch Regulation
Practical Counting Spot

This new location is what will be referred to as the practical counting spot. Basically, it has a new sweet spot.

Counting Point

With the balance now installed in the movement we have this extra length of hairspring that extends beyond the counting point and attaches to the hairspring stud.

Hairspring Stud
Hairspring Stud

When the movement is at rest the active length of the hairspring now extends all the way to the hairspring stud.

Because we know that the practical counting point on the terminal curve is the sweet spot for a zero rate. We need this extra length of hairspring for adjustments.

If there was no control in the movement to be able to get us back to that sweet spot or the counting spot, the movement would only be able to run slow and lose time.

That my friends are where the regulator pins come into play.

How Regulator Pins affect Watch Regulation

When regulating a watch, you set the regulator pins to the center of the regulator gauge. This should be right around the spot on the hairspring where the practical counting spot is.

When the hairspring is centered between the regulator pins must be straight and parallel to each other.

Hairspring At Low Amplitude
Hairspring At Low Amplitude

Regulator Pins and Hairspring at Low Amplitude

 When the balance starts rotating and is operating at a low amplitude the hairspring is barely opening and closing.  It’s either not touching or it’s just barely touching the regulator pins for very short periods of time.

At this point the movement will run to its maximum loss because the active length of the hairspring still extends all the way to the stud block.

Increased Amplitude Changes the Active Length of Hairspring

As the amplitude starts to increase the balance wheel will start getting a larger and larger arc of rotation.

 This will cause the hairspring to slowly start breathing in and out further and further until it gets to the point where the hairspring starts touching the regulator pins for longer and longer periods of time.

These longer periods of contact between the hairspring and the regulator pins slowly starts moving the active length of the hairspring away from the hairspring stud and starts moving it closer and closer to the regulator pins.

As the active length of the hairspring starts moving away from the hairspring stud and getting closer and closer to the regulator pins the rate starts speeding up the closer it gets to those regulator pins.

The Regulator Pin Controls the Counting Spot

Now the regulator pin is controlling the active length of the hairspring.

If you move the pins closer to the hairspring stud the rate will start slowing down. When you move the pins away from the hairspring stud the faster the rate becomes.

In Watch regulation ,if the regulator pins now are controlling the active length of the hairspring, why not just start off with the hairspring resting tight on one of the regulator pins instead of worrying about it being in the center?

Initially this does change the active length of the hairspring. It will cause the loss of time to be less when the movement is running at a low amplitude.

As the amplitude starts to increase the hairspring starts spending less time touching the regulator pin so that the regulator pin is no longer controlling the active length of the hairspring and starts moving the active length closer and closer to the hairspring stud again and the loss of time or slower rates start to slowly increase.

This problem is even compounded more when the movement goes into a vertical position.

where now the hairspring is being pulled down by the force of gravity.

Effects of Gravity on the Regulator pins and Hairspring

In the vertical position if the hairspring is already sitting on a regulator pin, it makes it much harder for the balance to throw the hairspring up to the other regulator pin.

 The hairspring spends more time off the regulator pin than it does touching it which moves the active length of the hairspring closer towards the hairspring stud.

 This will be different depending on the orientation of the hairsprings, whether they’re up or to the side or underneath the balance wheel.

To Summarize

In Watch Regulation, when a hairspring is centered between the regulator pins, wherever those regulator pins are becomes the end of the hairspring. Its what’s known as the active length of the hairspring.

Under those conditions if the regulator pins are sitting over the practical counting spot of the hairspring the rate will be zero.

 If you move the regulator pins towards the hairspring stud away from the practical counting spot the movement starts losing time. If you move the regulator pins towards the knee or the bend of the terminal curve of the hairspring the hairspring becomes shorter and the rates get faster.