Have you located a problem with an Impulse Jewel that needs replacing? In this video, I’ll provide you with tips and tricks for installing Impulse jewels perfectly every time. Impulse jewels play a critical role in the escapement. With their precisely crafted shape and smooth surface, they are responsible for transferring the impulse energy from the Pallet Fork to the Balance Wheel.

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Removing the Hairspring from the Balance Cock

To be able to reset an impulse jewel, we’re going to need to be able to get some shellac on it. That’s going to require us to remove the double roller.

To do that, we need to remove the balance wheel and hairspring. Start by loosening the hairspring stud screw, and then we just flip it over, take a probe, and push the hairspring stud right out of the balance cock. The balance wheel is free from the balance cock.

Mark the Position of the Hairspring

To begin, our first step is to remove the hairspring. Before doing so, I make sure to mark the position of the hairspring stud relative to its placement on the balance wheel. 

This serves as a reference point for its replacement. However, even with this reference point, it is unlikely that the replacement will be an exact match.

Marking the Hairspring Stud Location on Balance Wheel
Marking the Hairspring Stud Location on Balance Wheel

 Adjustments will still need to be made for the Beat Error, as it is difficult to position the new hairspring within a precision of a hundredth or even a thousandth of a millimeter. So don’t worry about it too much, you just want to get it close.

Remove the Hairspring with Levers

To remove the hairspring, I use hand-removing tools that I have refined, polished, and sharpened to fit smoothly under the collet.

Setting up the Staking Set 

Get the Impulse Jewel Reference Point

Having a reference point for the impulse pin’s direction relative to the balance wheel is crucial when reattaching it, just like the reference point for the hairspring. This is important in ensuring that the components are properly positioned during reassembly.

The K & D 18R Staking Set

In order to remove the double roller, I will utilize my K&D staking set, specifically the 18R model which is an improved version of the 18L Inverto set.

One of the advantages of Inverto’s is that the bottom die plate allows for the use of either a stump or stake, thus increasing the versatility of these staking sets.

K&D 18R Staking Set
K&D 18R Staking Set

The Adjustable Roller Table Remover

I particularly appreciate the 18R for another reason – it comes equipped with two adjustable roller table removers that will come in handy for removing double rollers with impulse jewels.

Setting up the Adjustable Roller Table Remover

The largest hole on the die plate is where the stump fits. This allows for the use of any stake to center this hole.

 After centering the die plate, tighten it up to secure it in place. The process involves inserting the stump into the aligned hole, followed by placing an L-shaped collar over the two jaws. The collars tab aligns with the center hole in the die plate.

Adjustable Roller Table Stump
Adjustable Roller Table Stump

The reason it’s adjustable is because as you turn, the wheel counterclockwise, the jaws either open or close. This makes it possible to use in all roller tables.

How the Adjustable Stump Works

The top part of the stump is flat. The idea is that the roller table is going to be supported by the flat part of the stump. This is going to enable the balance staff to be pushed out of the stump to release it.

Since it’s adjustable, the way it was designed allows you to hold the balance wheel and the roller table on top of the stump and turn it while the roller table is sitting on the stump.

How the Roller Table Sits on the Stump
How the Roller Table Sits on the Stump

What I like to do is do it under a microscope so I can see it closer. What you don’t want to do is tighten it so that it’s pushing down on the arm of the balance wheel. This can distort the balance wheel.

Selecting the Right Pusher

To drive the balance staff out of the double roller, you’re going to need a specially shaped punch. The one I like to use is called the cross-hole punch.

They are easy to identify in your staking set because there’s a hole running through punch by the tip. The hole is there in case you get a pivot stuck. It helps you to get it out.

Cross Hole Punch for Staking Set
Cross Hole Punch for Staking Set

In the staking set, there’s five of these. They start at number seven and go up to number 10. Seven being the smallest, number 10 being the largest.

How Hard do you Hit the Pusher?

One of the biggest mistakes that new users of staking sets make is hitting the pusher with too much force. This often ends with the watch part getting distorted.

I learned from a very early age that brass hammers apply too much force. Way more than is needed.  I prefer just using the back side of my tweezers. When you use your brass tweezers, you have much more control. You will be less likely to damage the impulse jewel if it’s still on the roller table.

You may have to tap it a few more times than you would with a hammer, but the one thing you’re not going to do is you’re not going to bend or break anything if you’re paying attention.

I would recommend using the tweezer method.

Be careful not to lose the Roller table and Impulse Jewel

One thing you want to be careful of is losing sight of parts when you’re removing them from the staking set.

Be very careful, you know these parts are easy to lose. If you touch it with the back side of your hand and move off your worktable, you’re going to lose it. You want to be very mindful of where the parts are.

Cleaning the Parts of all Shellac

Our next step is going to be to clean the impulse jewel and the roller table.  This will prevent the old shellac from interfering with the new shellac. I like to do it in these little dishes of denatured alcohol because it’s a little hotter than IPA.

Holding the impulse jewel with my tweezers, I take a very sharp piece of peg wood and just rub it on the jewel. I find that this is really one of the safest ways to do it because if it were to ping off, it’s not going to go very far.

To clean the roller itself, I just take it out and put it on a piece of watchmaker’s paper. Taking the peg wood, I just go over it and make sure there’s no residue of the old shellac left on the metal itself.

Once everything looks clean, then I just put them back into the denatured alcohol to rinse off any of the wood fibers that may be roller table or impulse pin.

Shellacking in the Impulse Pin to the Roller Table

With all our parts clean, we’re ready to shellac the impulse jewel to the roller table. Take the parts out of the denatured alcohol so you can get them dry before you start.

I like to put the roller table on my bench block so that it is sitting flat. I take some of the liquid shellac that we made back in the video I did on shellacking pallet stones, and we’re going to put just a little dab of this liquid shellac in our hole before we set the impulse jewel into the hole

Applying Liquid Shellac to Roller Table
Applying Liquid Shellac to Roller Table

Why I use Liquid Shellac to Set Impulse Jewels

Now there’s a couple of reasons I like to do it like this.

One, it gives you a little bit more open time to work with it because this liquid shellac is not going to get hard until I put some heat to it.

Secondly it ensures that the shellac is totally around the impulse pin in the hole.

Getting the Impulse Jewel into the Hole

Here’s another little trick that makes it easier to set the impulse pin in the hole. Use a needling tool with a little bit of spit on the tip of it.  Your impulse pin will stick to it very easily, and then you can maneuver it and stick it inside the hole.

Since the shellac is still soft, it’s going to hold the jewel in the hole.  and then you can just use one set of tweezers to hold the double roller, and another pair of tweezers to push the impulse pin down into the hole.

Picking up the Impulse Jewel
Picking up the Impulse Jewel

As you push down on the top of the impulse jewel, it will hit the bench block, and the flat side of the jewel will force it flat and perpendicular to the roller table.

Roller Table Heating Tool

You are going to need to heat up the shellac to set it. We are also going to need to add a little bit more to the other side of the roller table to set the jewel securely in place.

There is a special tool for heating roller tables.  You don’t have to have one. but they do come in handy.

Roller Table Heating Tool
Roller Table Heating Tool

The problem with them is that it’s spring-loaded. I’ve found the safest way to install a roller table into the tool is by using a very small smoothing broach to hold the roller. That way I can maneuver it into the tool, and I don’t have to worry about it flying away.

 Since the spring is tight, if it’s not in the jaw grooves perfectly, the jaws can snap together with the roller table flying about a mile

Don’t Put Roller Table in the Flame

Now, this tool is made of brass. You don’t want to directly put the roller table in the flame of the spirit lamp.  

If you remember the video I did on resizing the center coil of the main spring, we actually tempered that center coil. If you put the roller directly in the flame, it would apply too much heat to it and it would start tempering or softening the roller. You don’t want to do that.

Now, you can certainly find these tools on eBay, but you don’t really need one. You could literally take a piece of eighth inch brass plate and hold it with a pair of pliers. Hold that over the flame and it would do the same thing as the tool.

Adding additional Shellac to set the Impulse Jewel.

So again, I’m using a liquid shellac and I’m just applying a small dot right on the other side of the impulse pin. That will set and lock the jewel in place.

Using the Spirit Lamp

In my spirit lamp, I like to use denatured alcohol. I find that it burns very clean, doesn’t leave a lot of soot behind.

It doesn’t  take long for it to bring this up to temperature and then it will just check the shellac to see how well it flowed out. There was a little bit more shellac than it needed, so I just went ahead and chipped that off.

Inspecting Your Work

And now with the roller table back on the smoothing broach, I can inspect it to make sure that the shellac is not only hard, but neat and  that it’s holding the pin.

As we look at it from a side view, you want to make sure that the shellac bump is not too high.  That might interfere with the running of the escapement. This bump looks to be just fine.

Inspecting the Shellac Bump
Inspecting the Shellac Bump

You also want to check and make sure that there is no shellac on the sides of the impulse pin that would interfere with the jewel going in and out of the pallet fork. If there’s anything on there, it should just go right off.

Precautions When Reinstalling the Roller Table

When you’re installing the roller table, there’s two things you want to be aware of.

The first is the space where the double roller sits tight against balance staff. You want to make sure there’s no gap there between the roller and that spacer, otherwise your interaction between the impulse jewel and the pallet for itself or even the guard pin will not be correct.

The other thing is the space between the balance wheel arm and the die plate. If you were to try to drive the roller table onto the balance staff without the arm supported, you would crush the arm. The arm needs to be supported underneath by either a stump or punch.

Use Flat Face Hole Punches

We are going to look for a flat face hole punch that has a hole that’s a little bit larger than the balance staff itself. This one will be inserted into the die plate and used as a stump.

Lay the roller table back onto the balance staff and its correct orientation that we documented before we took it off.

Flat Face Hole Punch
Flat Face Hole Punch

Grab another flat hole punch that is one size larger than the one underneath the balance wheel and we’ll lay it in position over the balance staff.

We are going to slowly tap on the punch again with our tweezers to slowly drive it home. Look at this gap between the spacer and the bottom of the rope, that’s what I was talking about earlier.

Close that Gap
Close that Gap

You want to make sure that that’s tight and you get it down all the way.

Reinstalling the Hairspring

Now we need to press on our hairspring. Since we made an indication mark of the orientation of the hairspring stud, we can lay it back in position with the stud lined up with our mark.

The arm of the balance wheel is now going to lay flat on the die-plate.  When you press on the collet, all you really need to do is find the hole on the die-plate that’s just a little larger than the roller table.

Using a flat hole punch, we’re just going to put it right on top of the collet and give it a couple taps to seat it into place. And that’s all there is to that. Now we can reinstall the balance wheel on the balance cock.

This is just a matter of laying the balance wheel and hairspring into place and orienting the balance stud right over the hole where the balance stud screw is.

Reinstalling the Hairspring.
Reinstalling the Hairspring.

Once I’ve got it lined up, I just use my needling tool which is very to push through the hairspring. Just push the stud into the hole and then take my screwdriver and just tighten up the screw locking it in place.

Wind up the mainspring to a full wind and then we can drop the balance wheel back in the movement.

Frequently Asked Questions

What Does the Impulse Jewel Do

The term Impulse Jewel or Impulse Pin, typically refers to a specific part of a mechanical watch movement.

The impulse jewel is a small, precisely-shaped synthetic ruby that is located on the safety roller of the balance wheel. It receives energy from the watch’s balance wheel, which is a weighted wheel that oscillates back and forth.

It uses this energy to give a small “push” to the pallet fork, which is another part of the escapement. This action helps to control the release of energy from the mainspring and keeps the watch running accurately.

In short, the impulse jewel is a critical part of the watch’s escapement mechanism that helps to regulate the timekeeping accuracy of the watch.

Conclusion

Replacing the Impulse Jewel or Pin, is a fairly straight forward job. Your start by removing the hairspring and then the roller table from the balance staff.

The roller jewel and table are cleaned of all old shellac. I use a liquid shellac that I made to hold the impulse jewel in its hole on the roller table. Heat the roller table in a specially made roller table tool to allow the shellac to flow out and harden.

Then you want to inspect the shellac for proper application. Make sure the shellac bump is not too high and that the impulse jewel is free of any shellac.

Then the roller table and hairspring are reinstalled with the staking set.