1. The Escapement HOW TO DISTRIBUTE ENERGY AND INFLUENCE ISOCHRONISM

2. Table of Contents  What is an escapement?………………………..............................3  History and categories of escapements………………………….4-7  The components…………………………………..............................8-20  Glossary………………………………………………………………….21-30  Lubrication………………………………………………………………31-32  Phases and actions……………………………………………………33-36  Shocks of the escapement………………………………………….37-40  Escapement making………………………………………………….41-53

3. The escapement What is an escapement?  The escapement is a distributing organ. It releases energy to the regulating organ in equal measured increments. It sustains oscillation by delivering energy via the mainspring barrel and gear train.  Working in tandem with the regulating organ, the escapement counts the vibrations of the regulating organ so the stored kinetic energy in the mainspring can be released at a very precise rate.

4. The escapement categories of escapements: Recoil The recoil escapement features a balance and pallet that are joined and always move in unison. The term recoil refers to the fact that the escape wheel must rotate backwards or ‘recoil’ to allow each successive tooth to pass.  Examples include the verge, Brocot and Berthoud escapements.  The verge escapement was the first escapement used in watches and remained so for nearly 200 years. ►Although primarily used in clocks, The verge escapement was the only example of this category of escapement that was used in watches. These were the earliest escapements and were generally inefficient and the finest examples were only capable of accuracy of ~+/-5 minutes per day.

5. The escapement categories of escapements: Frictional rest Frictional rest escapements, like recoil escapements, feature a pallet and oscillator that are attached and rotate in unison. However, they differ from the recoil escapements in that they don’t require the escape wheel to rotate backwards in order for a tooth to pass. In this regard they are more efficient. The drawback of this category is in the name: friction. While the balance wheel is in its supplementary arcs, the escape wheel teeth are in contact with the staff and under constant friction. This results in a loss of energy to the balance and considerable wear that necessitated frequent service, especially with the cylinder escapement.  Until the introduction of the lever escapement, the cylinder and duplex escapement were found in most watches. Some of the higher quality duplex escapements made by British watchmakers were capable of results that rivaled the early lever and detent escapements. ►Capable of slightly better accuracy than the verge escapement, but allowed for a better power curve and slightly less wear.

6. The escapement categories of escapements: Detached Detached escapements feature a balance wheel that is separate or ‘detached’ from the pallet. During the supplementary arcs of the balance the escape wheel is locked with the pallet and there is no contact with the balance. This system allows for very little disturbance of the isochronism of the oscillator and also very little wear.  The Swiss lever escapement was invented in 1750 by Thomas Mudge. It has since come to be used in the vast majority of modern mechanical watches.  Examples include the Swiss lever escapement, the detent escapement and the co-axial escapement.

7. The escapement Through a process of evolution over more than 250 years, the Swiss lever escapement has become the primary escapement used in watches today. Virtually all modern watches use some version of it because of its accuracy, reliability and ease of manufacturing. Various safety mechanisms incorporated into its design allow it to be far more shock resistant than other escapements. Adjustable and repairable or replaceable components and jeweled pallets allow for a mechanism that outlasts its predecessors. While there is a need for repair on timepieces featuring other escapements such as the cylinder escapement and the detent escapement, their age and scarcity make it possible that many watchmakers will never have a chance to even work on them. New escapements that are exclusive to specific brands also need service but the brands that make these watches will provide training to those that they have provided spare parts accounts. For these reasons, we will focus our repair training on the Swiss lever escapement.

8. Components:

9. A.Escape wheel tooth (Impulse plane)

10. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane)

11. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor

12. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor D.Exit stone (impulse plane)

13. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor D.Exit stone (impulse plane) E.Guard pin

14. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor D.Exit stone (impulse plane) E.Guard pin F.Banking pins

15. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor D.Exit stone (impulse plane) E.Guard pin F.Banking pins G.Roller jewel (impulse pin)

16. Components: A.Escape wheel tooth (Impulse plane) B.Entry Stone (locking plane) C.Pallet arbor D.Exit stone (impulse plane) E.Guard pin F.Banking pins G.Roller jewel (impulse pin) H.Safety roller

17. Components Pallet Stones: The pallet stones are a pair of stones that are held to the lever arms with shellac and a light friction fit that intermittently lock and receive impulse from the escape wheel. The escape wheel makes contact with the stones loud enough for the human ear to hear from over a foot away anywhere from 18,000 to 36,000 times per hour so the pallets must be very hard to resist wear and breakage. Usually they are made from synthetic sapphire or ruby but some manufacturers are now using silicon to further strengthen them. The angle at which the impulse planes are cut is dependent largely on the frequency of the individual timepiece.

18. Components Bankings: Banking pins serve to limit the lateral movement of the pallet fork. Bankings come in two styles: banking pins and solid bankings. Banking pins are vertical pins that are pressed, riveted or threaded into the mainplate. The benefit to pins is that they are adjustable. Some are even eccentric so they can be adjusted by turning them like a screw. Solid bankings are machined into either the mainplate or the pallet bridge. They are not adjustable therefore they must have very tight tolerances in order to function properly.  Banking pins should only be adjusted when the horn shake needs to be corrected.

19. Components Rollers: The roller is a cylinder with a disc that holds the roller jewel that is friction fit to the lower half of the balance staff. Rollers come in two main styles: Single and double rollers. The primary difference between the two is that the double roller has a smaller lower second diameter called the safety roller that features a crescent cutout of its rim whereas the single roller has only one diameter that features the cutout. The single roller is generally used in thinner watches where space is at a premium. The majority of modern watches have a double roller. Roller Jewel: The roller jewel, which is held to the roller table with shellac, can be half-round or triangular. It is important that it be small enough to fit into the slot of the fork without binding but also have a minimum of play.

20. Components The Guard Pin: The guard pin, or dart as it is sometimes called, is a small protrusion on the underside of the fork that protrudes out centered in the fork slot. Its purpose is to prevent the watch from overbanking in the event the watch receives a shock while the balance is in the supplementary arcs by contacting the safety roller. It can be attached to the fork through a friction fit, it can be riveted and in some rare instances it can be threaded and attached with a screw. In the case of a watch with a single roller the guard pin will be in a vertical orientation. Regardless of the design, it must be straight, flat and perfectly centered in the slot.

21. Glossary Angle of lift: The angle traveled by the balance in which the pallet is in motion, during which the isochronism of the regulating unit is disturbed. This angle is generally between 38 and 55 degrees. This angle is used as a known variable that is programed into a timing machine in order for it to calculate amplitude.  When the angle of lift is properly programed into a timing machine, it allows the machine to determine the amplitude of a watch by calculating the period it takes for the 5 shocks of the escapement to occur based on the angle in degrees to which the escapement is manufactured. Supplementary arc: The angle traveled by the balance when it is not in contact with the escapement. During this time the pallet and escape wheel are locked. It is divided into two separate actions: The ascending supplementary arc, when the balance is rotating away from the escapement and the descending supplementary arc, when the balance is rotating towards the escapement. It is the angle in which the balance travels between its two extremes minus the angle of lift.

22. Glossary Entry and Exit: Rather than left and right, the sides of the escapement and its components are referred to as entry and exit to avoid confusion arising from the direction in which the component is being viewed. Entry and exit refer to the direction the escape wheel turns. The entry side is the side that will be interacted with first in a cycle as a given tooth moves through the actions of the escapement. Any part on the leading side is referred to as entry and any part on the trailing side is referred to as exit. Beat: A watch is said to be “in beat” when a straight, imaginary line can be drawn that bisects the balance staff, roller jewel, pallet staff and escape wheel arbor; this creates a state of equilibrium where the actions of the escapement are completed in equal periods on either side of the escapement.  A “beat error” of zero means there is perfect centering of the roller jewel in regards to this line and the “tick” and “tock” of the escapement are equal. When “in beat” the escape wheel teeth will come to rest on the impulse plane of a pallet stone, this allows the watch to start with no assistance when wound or in the event the watch receives a shock capable of counteracting the rotation of the balance, stopping the watch.

23. Glossary Lock: Lock is the state in which the pallet is at rest on a banking during the supplementary arcs, held by the force of the mainspring by the mechanical action of the escape wheel acting on the pallet stone locking face (draw). Drop: The distance an escape wheel tooth travels after it has slipped off of the impulse plane of a pallet stone and the next tooth falls onto the locking plane of the following stone.  The precise depth of the escape wheel tooth on the stone at the precise moment it contacts the locking plane is referred to as drop or initial lock.

24. Glossary Run to banking: Also referred to as backlash or lost way, This is the distance a pallet stone travels down an escape wheel tooth immediately after lock occurs. This motion is limited by the point the pallet lever comes to rest on the banking. Total lock: The depth of penetration of the escape wheel on the pallet stone after drop when the pallet comes to rest on the banking.  The total lock is the drop plus the run to the banking.

25. Glossary Draw: A mechanical force exerted on the locking face of a pallet stone by an escape wheel tooth that prevents unlocking of the escapement due to shock or gravity. The angle is generally 12-16 degrees.  If the watch receives a shock large enough to cause the pallet to lift off of a banking, the force of draw will cause it to return to the banking. This is also the force that the balance must overcome in order to unlock the fork.

26. Glossary Recoil: The backward motion of the escape wheel.  Geometric recoil: When the pallet unlocks, the escape wheel reverses at an angle of ~0°,15’ due to the rectangular shape of the pallet stone. This is the action of the pallet overcoming the force of draw.  Dynamic recoil: This is reversing of the escape wheel at an angle of ~0°,00’15” due to the inertia of the escape wheel when it starts to rotate again as it clears the corner of the pallet stone.

27. Overbanking: Overbanking is a condition where the pallet and roller jewel have come out of engagement and the roller jewel is lodged against the back of the fork and unable to enter the fork slot. When overbanked, the balance and pallet cannot move and the watch will not run. Overbanking can be caused by various faults in the escapement such as a missing or damaged guard pin or fork horn, excessive guard pin clearance, excessive endshake of any combination of the escape wheel, pallet and balance or improper divisions of the same. A watch can also become overbanked if the balance is installed in a manner that the fork is on the wrong banking for the roller jewel to enter the slot. Glossary

28. Knocking: Also called rebanking, knocking is a condition caused by excessive energy being released to the balance resulting in the roller jewel traveling far enough to hit the back side of the fork at the end of its ascending supplementary arcs. Knocking can be identified by an intermittent galloping sound in the watch, this sound is the roller hitting the back of the fork. Because the balance’s travel is being interrupted by the fork it will immediately stop and reverse direction. This means the balance will complete its cycle faster thus increasing the rate of the watch. Glossary ►Because knocking is the result of too much amplitude, the amplitude must be decreased in order to correct the problem. The ideal methods are to increase the penetration of the pallet stones into the escape wheel equally or to replace the mainspring with a weaker (thinner) one.

29. Glossary Isochronism: The tendency of a phenomenon to occur at equal intervals, irrespective of outside influences (amplitude, temperature, air pressure). In the case of watches, this is represented by the balance wheel taking the same amount of time to complete each vibration regardless of the amplitude. As watchmakers, we are attempting to achieve isochronism by reducing the effect of these outside influences. However, the Swiss lever escapement is itself an outside influence when it comes to the regulating unit. The balance and pallet have a reciprocal relationship consisting of a series of movements imparting and receiving kinetic energy, referred to as “impulses”.

30. Glossary ►A represents the dead point; the point that the roller jewel comes to rest when there is no power on the movement. ►From point B to C, or unlocking, the roller jewel enters into contact with the lever notch of the Fork. This is a resistance before the dead point that results a loss of isochronism. ►At point C the roller jewel is impulsed by the fork slot. This is an impulse before the dead point that results in a gain. ►At point C’ the impulse from the lever continues after the dead point. Any impulse after the dead point results in a net loss. ►Greater amplitude and a smaller lift angle will both reduce these errors. Conclusion: The sum of losses are greater than the gains, the result is that the Swiss lever escapement will always produce a loss of isochronism. Isochronism:

31. The Swiss lever escapement is subject to unique stress compared to the rest of the watch. With every swing of the balance through the fork a pallet stone has a large impact followed by a strong sliding force, because of these unique forces the pallet stones receive special lubrication. Regardless of what grease is used, epilame should be applied to the pallet stones and the watch should be run with no additional lubrication for 15 minutes. The epilame creates a film on the impulse plane of the stones that creates a surface tension Lubrication such that oil is repelled. By running the watch without grease on the stones the escape wheel teeth will scrape off the epilame coating leaving a channel that is not treated causing the grease to remain in the channel on the impulse plane where it is most effective. Grease can them be applied to the impulse planes of the pallet stones directly or to the escape wheel teeth which will then distribute the grease when running.

32. The three types of grease that are commonly used on pallet stones are as follows:  Moebius 9415: This special grease features thixotropic properties meaning it behaves like a heavy grease when static but when agitated, like when an escape wheel hits it, it becomes less viscous and more like an oil. These properties provide a cushioning effect as well as a smooth sliding action as the tooth slides on the locking and impulse planes. 9415 is for use in high beat ( =/> 28,800vph) watches  Moebius 941: Similar to 9415 but This grease is formulated for use in low beat watches (< 28,800vph)  RL-2: A proprietary Grease used by Roles that features the same thixotropic properties of the Moebius greases but has a more uniform consistency that allows it to function well in low and high beat watches. It also behaves very well with epilame allowing for better control. Lubrication

33. Actions of the escapement The locking Phase : BalancePalletWheel OscillatingLocked The pallet and escape wheel are not moving. The geometry of the two parts acting on one another under the power of the mainspring holds the pallet firmly against the banking. The balance is in its ascending or descending supplementary arc under the power of the hairspring Power flow: Mainspring Balance

34. Actions of the escapement The unlocking Phase : BalancePalletWheel OscillatingLocked Unlocking Recoil The roller jewel enters the fork slot under the power of the hairspring. This causes the fork to unlock. Due to the locking surface of the pallet moving, the escape wheel begins to recoil. Power flow: Mainspring Balance

35. Actions of the escapement The impulse Phase : BalancePalletWheel OscillatingLocked Unlocking Recoil ImpulsedImpulse The escape wheel tooth falls onto the impulse face of the pallet stone. The angle at which the two meets causes the escape wheel, under the power of the mainspring, to push or impulse the pallet lever. The pallet in turn impulses the roller jewel via the fork slot. Power flow: Mainspring Balance

36. Actions of the escapement The safety Phase : BalancePalletWheel OscillatingLocked Unlocking Recoil ImpulsedImpulse OscillatingRun to bankingDrop The escape wheel tooth falls off of the impulse face of the pallet stone, allowing the next tooth to drop onto the locking plane of the other stone. The fork continues to travel until it lands on the banking. The balance enters its ascending supplementary arc. Power flow: Mainspring Balance

37. The shocks of the escapement There are five total shocks that occur during one vibration of the balance wheel. Although they happen so fast in succession that your ear can only make out one “tick” or “tock”, they each represent an important. action of the escapement. When viewed through an oscilloscope, the sound can be seen in a graph like this:

38. 1. The first shock is produced by the roller jewel entering the slot. The shocks of the escapement

39. 2 + 3 The next sound is actually a combination of two shocks. First, The Escape wheel tooth falls off of the locking plane onto the impulse plane. Then immediately after, the fork catches up with the roller jewel and the slot of the fork hits the roller jewel from behind. The shocks of the escapement

40. 4 + 5. The last sound is also produced by two different shocks happening almost simultaneously. The escape wheel tooth falls onto the locking plane of the pallet stone followed by the pallet lever hitting the banking. These two combine to make the largest sound in the escapement. The shocks of the escapement

41. Escapement Making There are several components in the Swiss lever escapement that can be adjusted for optimal performance. The process of checking and adjusting these factors is called “escapement making”. All checks and adjustment should be performed during disassembly so cleanliness is not compromised.

42. Escapement Making Checks: All parts should be visually inspected during disassembly. The primary areas we are looking at and what we are looking for are as follows: Fork horns  Make sure both horns are flat and parallel Fork Slot  Inspect the inside of the slot for damage caused by a damaged or ill fitting roller jewel.

43. Escapement Making Guard pin  The guard pin should be straight with the point at the end directly in the center. Pallet staff  Tight enough that it shouldn’t be able to move in its hole without a Horia tool or staking set. Both pivots must be present, clean and mirror polished. Pallet lever  Must be straight and flat Roller jewel  The roller jewel must be clean and free of cracks and chips.  Check that the roller jewel is not loose in the roller

44. Escapement Making Pallet stones  Impulse faces must be perfectly flat Check that no grooves have been cut in the face  Must be free of chips and cracks  Stones must be flat and parallel with the top side of the lever Shellac  Shellac should cover the back side of stone and a good deal of the back side of the pallet arm but not all the way to the edges.  Shellac must fill the gap behind the stone between it and the fork, and must not protrude onto the top of the fork and stones.  Burnt, dirty or crumbling shellac should be cleaned of with denatured alcohol and new shellac applied

45. Escapement Making Escape wheel  The escape wheel must be true and flat with both pivots in tact and mirror finished.  Inspect that teeth for damage. The impulse faces of the teeth should be perfectly flat with no defects in their surface. Any defects will cause drag and can cause irregular action resulting in stoppage. Bankings  Bankings should be smooth and have no inconsistency in the surface where the lever contacts the bankings.

46. Escapement Making The first check after ensuring the condition of all components is the endshakes and divisions of all components. Endshake is the amount of vertical space between an upright component and its bearings.  Always adhere to the manufacturers specified tolerances if published. If not, as a rule, the balance, pallet and escape wheel should have less endshake compared to the train and should all be equal to one another. Divisions are the vertical relationships of two or more parts in relation to one another. In the case of the Swiss lever escapement we need to ensure that:  The escape wheel teeth are hitting between the center and upper third of the height of the pallet stones.  The Roller jewel penetrates deep enough into the slot that if the watch receives a shock the roller won’t be able to come out of engagement with the slot.  Roller jewel must not be so deep as to touch the guard pin.  The guard pin must be in line with the safety roller.

47. Escapement Making After the endshakes and divisions have been checked, you can begin inspecting and, if need be, correcting any errors. Horn Shake: Horn shake is the lateral distance that the fork travels from its position of rest on a banking until the inside edge of a fork horn makes contact with the roller. This is a safety angle that prevents the escapement from becoming unlocked during the supplementary arcs of the balance while the guard pin is inside the safety crescent.  First, Check that horn shake is even and minimal on both sides. The horn shake can be observed by the following procedure: move the balance wheel until the escape wheel tooth falls onto the locking plane of the next jewel. Continue to rotate the wheel about one- eighth of a turn and with a pegwood move the pallet fork side to side. The movement of the fork is the horn shake. Repeat this process on the other side of the escapement.  If the horn shake is not correct, the amount can be adjusted by moving the banking pins. Closing the distance between them will reduce horn shake and increasing the distance will increase horn shake. If horn shakes are unequal the banking pins can be adjusted individually to create symmetry.  If the watch has solid bankings and therefore no banking pins, the pallet bridge would need to be replaced if worn.

48. Escapement Making Guard pin shake: Guard pin shake is the lateral distance that the fork travels from its position of rest on a banking until the guard pin makes contact with the safety roller. This is a safety angle that prevents the escapement from becoming unlocked during the supplementary arcs of the balance if the watch were to receive a shock.  The guard pin shake must be smaller than the horn shake; it can be checked by rotating the balance wheel so that the roller jewel is outside of the fork in a position analogous to it’s position in a supplementary arc. Move the pallet fork side to side as before, and the movement of the fork is the guard pin shake. Once again continue this process as before to the other side of the wheel. But also make sure to check it in multiple places around the balances rotation to verify that the roller is true.  The amount of guard pin shake can be adjusted by lengthening or shortening the guard pin. Most commonly the fault will be that the guard pin shake is unequal. In this case the guard pin must be straightened to create the same amount of play on either side of the balance.  Never attempt to adjust the guard pin shake by adjusting the banking pins. This will result in faults being introduced elsewhere.

49. Escapement Making The last step to escapement making is depthing the stones.  To check the stones, slowly move the balance until the escape wheel tooth falls onto the locking plane of the jewel. This is initial lock or drop. Be sure that the tooth does not fall directly onto the impulse plane, the teeth must land on the locking plane with a certain amount of clearance for safety. Continue rotating the balance. The movement from initial lock to its stopping point is known as “run to the bank”. The complete distance is known as “total lock”. Total lock is generally one-quarter of the locking plane but can be more or less depending on quality and size. Initial lock, run to the bank, and total lock should be even on both the entry and exit stones. (This method of checking the depthing of the escapement by turning the balance wheel is an initial check only. To verify the proper depthing it needs to be repeated with the balance wheel removed and by guiding the pallet slowly with a plastic stick.)

50. Escapement Making Pallet stone depthing  Proper, equal depthing can be achieved by warming the pallet with a pallet warmer on an electric heater or alcohol lamp to soften the shellac. Once the shellac is soft the stones can be pulled or pushed with a pair of tweezers until the stones are in the desired positions. Once removed from the warmer the shellac will cool and harden almost immediately.  Never attempt to adjust the depthing of the stones by adjusting the banking pins. This will result in other faults being introduced elsewhere.  Proper depthing is a balancing act of initial lock (drop), total lock and run to banking. Any change to one of these elements on one stone will have an inverse effect on other aspects of depthing. Before making a correction to a stone, look at the other stone and reason through what the impact will be on this stone. If only one stone is worked on without respect for the other the result will be a frustrating series of alternating adjustments back and forth between the two stones.

51. Escapement Making Pallet stone depthing  A tool called an escapement meter can be used to adjust the depth of the stones. This allows for constant accurate measurement of the corrections being made so you know how much you have moved a stone in the adjustment process.

52. Escapement Making Pallet stone depthing PRACTICAL AND SIMPLE INSTRUCTIONS FOR AN ESCAPEMENT MAKING What Not To Do:  Never begin to check or adjust escapement starting from the pallet stones.  Never attempt to correct the clearance of the guard pin by means of the banking pin.  Do Not correct run to banking by moving (bending) banking pins. What To Do:  Start from checking and adjusting the horn shake.  Adjust positions of banking pins according to the horn shake.  Check and if necessary adjust guard pin shake  Run to banking must be adjusted by moving pallet stones.  Adjust pallet stones penetration according to the minimum of locking, and run to banking positions.

53. Escapement Making PRACTICAL AND SIMPLE INSTRUCTIONS FOR ESCAPEMENT MAKING Drop:  The drop is a necessary safety. Its linear value varies between 0.05 0- 0.10 mm. And for angular valve is 0.30’ – 1.  The drop causes loss of power; therefore, it should be equal on both sides and not too large.  When outside drop is too large, it means that pallet arms are too narrow.  When inside drop is too large, it means that pallet arms are too wide.  When both drops are too large, it means that the teeth clubs are too small. General rules:  Horn shake must be as small as possible, and equal on both sides.  The only time and condition when we should straighten (or bend) the banking pins is when adjusting horn shake.  Guard pin shake must always be smaller than horn shake, and equal on both sides.  Run to banking should be smaller than horn shake, and equal on both sides.  Locking position must be slightly larger than horn shake  Locking divisions should be about 1/4 - 1/6 of the length of pallet stone impulse surface. Penetration might be smaller or larger depending on the limits and needs of the amplitude.