School Watch Project

Transcript School Watch Project

SWISS AMERICAN WATCHMAKERS TRAINING ALLIANCE

SCHOOL WATCH PROJECT Year One

Overview

Equipment, Tools: DeltaCad drawing.

Teaching Time: 20 minutes Practical Class Time: discussion only Distribute drawing “School Watch Design”: - discuss the general approach to the school watch project.

The project will be broken down into 8 segments: 1) preparing the work piece.

2) forming steady pin and screw holes, recesses.

3) forming oscillator and gear train holes and recesses.

4) forming ratchet, crown wheel recesses, modifying crown wheel.

5) forming the click and click spring recesses.

6) forming the click and spring.

7) forming the winding and setting recesses.

8) shaping the bridge, application of final surface finish.

Overview Drawing “School Watch Design”

Segment 1: Preparing the workpiece

Step 1 Disassembly of 6497 Movement

Materials: new 6497-1 movement.

Equipment, Tools: basic watchmaker’s hand tools.

loupe.

Teaching Time: 5 minutes Practical Class Time: 25 minutes Distribute a new 6497-1 movement to each student.

Fully disassemble the movement: - store balance complete safely away.

- remove balance setting from the mainplate.

- store individual components safely away.

Have ready at bench: - the stripped mainplate - jewels may be left in place, and later removed as needed.

- the barrel bridge.

- the train bridge.

Step 2 Preparing the Raw Stock

Materials: 1 sheet of 12” x 12” x .0800” brass flat stock (2.06 mm thick).

Equipment, Tools: band saw.

sharpie.

ruler.

loupe.

#2 hand file.

Teaching Time: 1 minute Practical Class Time: 59 minutes Collect a piece of the 12” x 12” brass flat stock.

Trace a grid pattern of 47 mm x 60 mm rectangles onto the brass (can form 30 such rectangles).

Cut out the rectangles on the band saw so that they are slightly larger than 47 x 60.

Distribute a rectangle to each student.

File the shapes to completion to 47 mm x 60 mm.

Deburr all edges of work piece.

Step 3 Preparing the template

Materials: .0800” brass rectangle.

DeltaCad drawing.

Equipment, Tools: scissors.

glue.

jewelers saw and blade.

bench vise.

saw table.

prick punch.

watchmakers hammer.

#4 half-round file.

Teaching Time: 1 minute Practical Class Time: 59 minutes Distribute drawing “6497 Template Shaping.dc’’: - print directly from DeltaCad to print to scale.

- print on transparency film.

- cut out drawing just outside the rectangle borders.

- center and glue the black rectangle borders to the outer shape of the brass piece.

Cut out the irregular portion of the template shape: - do not cut inside of the black border lines.

- cut directly on the lines (the circle represents the bridge diameter).

- form a prick punch in the center of the center hole.

- remove the transparency.

Deburr all edges of the work piece.

Step 4 Drilling the Center Hole

Materials: workpiece.

Equipment, Tools: drill press.

center punch.

watchmakers hammer.

Ø 1.00 drill bit.

countersink.

loupe.

Teaching Time: 1 minute Practical Class Time: 1 hour (depending on availability of drill presses) Drill a Ø 1.00 hole through the center wheel marked location: - enlarge the prick punch with a center punch.

- drill the hole, deburr.

Ø 1.00 is undersized enough that centering errors will be corrected later on the face plate when forming the center hole.

This hole will be used to center, rotationally position, and attach the mainplate to the workpiece.

Step 5 Securing the Workpiece to the Mainplate

Materials: workpiece.

mainplate.

DeltaCad drawing.

Equipment, Tools: glue.

Ø 1.00 drill bit.

loupe.

Teaching Time: 5 minutes Practical Class Time: 25 minutes Distribute drawing “6497 Template Positioning’’: - attach the mainplate, dial side facing out, to the workpiece via a Ø 1.00 drill bit through the center holes. The center jewel should be in the mainplate.

- rotate and position the mainplate so that it is oriented to the workpiece shape as indicated in the drawing.

Secure the pieces together: - ensure drill bit is perpendicular to both pieces before gluing.

- apply glue in several spots to ensure security.

- apply glue to outer perimeter – no need to apply glue to internal portions of the mainplate.

- allow the glue to cure.

* Note: this drawing, and all subsequent drawings may not be used for determining the locations of holes or recesses for the ¾ bridge, except as specifically indicated in the procedures.

Step 5 Drawing “6497 Template Positioning”

Rotate and position the mainplate so that it is oriented to the workpiece shape as indicated in the drawing.

One measure of this is the 3 rd /4 th wheels are on a line that roughly bisects the round cutout.

The drill bit should be perpendicular to the mainplate before gluing the mainplate to the workpiece.

Segment 2: Forming steady pin and screw holes, recesses

Step 6 Identifying Steady Pin and Bridge Screw Holes

Materials: work piece/mainplate.

DeltaCad drawing.

Equipment, Tools: two sharpies of different colors.

prick punch.

watchmakers hammer.

loupe.

Teaching Time: 15 minutes Practical Class Time: 45 minutes Hand out drawing designating steady pin and screw hole locations: “Steady Pin, Screw Locations” Discuss, identify the locations for all steady pins and bridge screws.

- note the 7 th hole which will not have a pin fitted into it. It is used for attaching the original barrel bridge to the workpiece in order to center the crown wheel recess, and to position the sliding and winding pinion recesses.

Mark all steady pin holes in the mainplate with one color: - put a sharpie dot of same color in new locations to be drilled.

- locate these 3 new holes as depicted in drawing; slight positional errors are acceptable.

Mark all screw holes in the mainplate with another color: - all locations are original screw holes.

It is recommended everyone in the class use the same colors (i.e. all screw holes green and all steady pin holes red, etc.) Note: as color gradually rubs off, replenish as needed.

Instructor should inspect each workpiece before continuing.

Step 6 Drawing “Steady Pin, Screw Locations”

the "7th" location - will not have a pin inserted for final assembly original steady pin locations new steady pin location (mark with sharpie) set lever screw hole © 2011 SAWTA new steady pin locations (mark with sharpie) original bridge screw locations

Step 7 Drilling the Steady Pin Holes

Materials: workpiece/mainplate.

Equipment, Tools: drill press.

center punch.

Ø .95 drill bit.

loupe.

countersink.

Teaching Time: 5 minutes Practical Class Time: 2-3 hours (depending on availability of drill presses) Drill out the three new steady pin locations: - prick punch, then center punch these locations.

- drill straight through the metal of both pieces for these holes.

Drill out the remaining four steady pin locations: - feed drill bit through steady pin holes in mainplate.

- all holes are slightly undersized to be broached out later.

Deburr holes on exposed side of workpiece, after each drilling, so that it continues to seat flush to drill press.

Depending on availability of drill presses, this may take a few hours for the entire class to finish this step.

Step 8 Drilling the Screw Holes

Materials: workpiece/mainplate.

Equipment, Tools: drill press.

Ø .75 drill bit.

Ø 1.25 drill bit.

loupe.

countersink.

Teaching Time: 10 minutes Practical Class Time: 2-3 hours (depending on availability of drill presses) Drill out the five bridge screw locations with the Ø .75 drill bit: - ensure drill bit is spinning true before using.

- optically center the drill bit in the holes without spinning it.

- when certain drill bit is not touching the threads, lower it one last time to bottom out on the workpiece, without it spinning.

- have a partner turn on the drill press while bottomed out.

- ideally, drill through without backing out. If you feel you must back out, have partner turn off drill press before retracting bit.

- repeat centering step before continuing to drill.

- when drill bit breaks through, have partner turn off the drill press before retracting drill bit.

When the above procedures are followed, the threads in the mainplate will not be damaged.

Drill out the set lever screw hole to completion with the Ø 1.25 drill bit.

Deburr holes on exposed side of workpiece, after each drilling, so that it continues to seat flush to drill press.

Depending on availability of drill presses, this may take a few hours for the entire class to finish this step.

Step 9 Separating the Pieces

Materials: workpiece/mainplate.

acetone.

Equipment, Tools: 2 colors of sharpie.

countersink.

Teaching Time: 1 minute Practical Class Time: 29 minutes Separate the pieces: - soak them in acetone to break the glue bond.

- some rubbing or scrubbing will expedite the process.

- remaining residue is fine as long as all glue is removed from the train side of mainplate, and the underside of the workpiece.

Label the sides of workpiece “top” and “bottom”, respectively.

Deburr remaining sides of all drilled holes.

Mark the screw and steady pin holes in both pieces: - circle the screw holes with one color and the steady pin holes with another color.

- do this on both sides of each piece.

Step 10 Enlarging the Screw Holes

Materials: workpiece.

Equipment, Tools: drill press.

Ø 1.25 drill bit.

countersink.

loupe.

sharpie.

Teaching Time: 1 minute Practical Class Time: 59 minutes (depending on availability of drill presses) Drill the screw holes in the bridge to final size: - the Ø 1.25 size exists for 2 reasons: 1) allow for thread clearance.

2) the counterbore used to form the screw head recesses requires a Ø 1.25 pilot hole for centering.

Deburr both sides of the screw holes.

Re-mark holes with sharpie if the color was removed.

- ensure set lever screw hole is labeled such that a screw head recess will not be cut into it.

Step 11 Forming the Screw Head Recesses

Materials: workpiece.

Equipment, Tools: staking set.

counterbore.

depth stop.

caliper.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1-2 hours (depending on availability of counterbores) Cut the five bridge screw recesses to depth with the counterbore: - a fairly strong feed force is required.

- depth = screw head height + chamfer depth + amount that bridge will be faced off by in the finishing process.

- practically, this depth = 1.27 mm.

cut recess onto side of workpiece marked “top.” - measure depth of first recess with butt end of caliper.

- adjust depth step to be flush to top of staking base after first recess is completed.

- cut remaining recesses until depth stop seats to top of staking base.

Do not cut a recess into the set lever screw hole.

Deburr recesses (chamfering will be the final step).

This may take a few hours depending on the number of counterbores available to share.

Step 12 Forming the Steady Pins

Materials: Ø 1.00

blued steel.

Equipment, Tools: watchmaker’s lathe.

graver.

caliper.

loupe.

Teaching Time: 5 minutes Practical Class Time: 55 minutes Part off 6 pieces of the Ø 1.00 steel round stock to length: - hold graver perpendicular to steel to part it off.

- face off each piece to 3.20 mm overall length.

- strongly round or bevel each end.

The pins will be shortened later to final length, and the ends will be rounded and polished.

Step 13 Enlarging the Steady Pin Holes

Materials: workpiece.

mainplate.

Equipment, Tools: small cutting broach.

sharpie.

Ø 1.00

blued steel.

countersink.

loupe.

Teaching Time: 5 minutes Practical Class Time: 55 minutes Enlarge the steady pin holes to accept the steady pins: - steady pins are to be a friction fit.

- broach from the underside of the workpiece (the direction that the pins will be inserted).

- broach first hole until Ø 1.00 blued steel stock starts to enter the hole slightly, then stop broaching.

- re-insert broach to cutting depth, mark border of broach with a sharpie to define depth of cut.

- broach remaining holes until the color mark on broach becomes flush to workpiece.

Later, when inserting the steady pins, if it is found that they are going in too tightly, one can broach slightly more.

Broach the three drilled holes in the mainplate: - steady pin material slides into hole with no radial play.

broach the “7 th” steady pin hole in same manner.

Deburr holes, re-mark with sharpie.

Step 14 Forming a Steady Pin Pusher

Materials: Ø 3.00 steel.

Equipment, Tools: watchmaker’s lathe.

graver.

Ø 1.00 drill bit.

pin vise.

cutting fluid.

caliper.

loupe.

The tool has three purposes: 1) keep the pin upright when installing.

2) prevent damage to pins.

3) insert pins to a uniform depth.

Step 15 Installing the Steady Pins

Materials: workpiece.

6 steady pins.

Equipment, Tools: small cutting broach.

jewelling tool.

steady pin pusher.

cutting broach.

loupe.

Teaching Time: 5 minutes Practical Class Time: 60 minutes Install steady pins into the workpiece: - insert steady pin pusher into jewelling tool.

- hold steady pin in the hole of the steady pin pusher.

- lower pin/pusher to the hole of the workpiece.

- insert steady pin partially.

- if strong resistance is felt, remove, broach slightly more.

- fit pin until pusher seats flush to workpiece.

do not fit a pin into the “7 th” hole.

Test fit of bridge to mainplate: a slightly “sticky” fit is acceptable.

- if the bridge does not fit, this is typically due to steady pins not being perpendicular to workpiece.

Segment 3: Forming oscillator and gear train holes and recesses

Step 16 Tracing Outline of Bridge Diameter

Materials: workpiece.

mainplate.

Equipment, Tools: scribe.

loupe.

Teaching Time: 1 minute Practical Class Time: 5 minutes Trace outline of bridge diameter onto workpiece: - secure mainplate to workpiece.

- trace a light line around diameter of mainplate.

- take into account the two diameters of the mainplate.

- use the smaller diameter ( Ø 36.55).

This will be a visual landmark: - aids in positioning jaws of face plate.

- aids in knowing where the limit is to cut into the brass.

- aids in sawing off irregular shape.

Step 17 Preparing Cutters

Materials: HSS steel.

Equipment, Tools: grinder.

eye protection.

india stone.

arkansas stone.

caliper.

Ø 1.20 drill bit.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1 – 2 hours (depending on availability of grinders) Discuss parameters for forming cutters: distribute drawing: “Boring Cutter” - grind back the underside and backside of the cutter.

- modify two existing cutters in order to save time.

- the side relief angle may need to be increased.

- both cutters must be of the same size HSS shank in order to maintain cutter height.

- have a sample small cutter to pass around.

- perform demo as needed.

Form the two cutters: - smaller cutter for boring holes: - cutting width and height must fit through a Ø 1.20

hole with only the tip making contact – have a drilled Ø 1.20 hole at hand to fit cutter into.

- larger cutter for recesses: - cutting width and height approximately three times larger than smaller cutter.

- the cutting portion needs to be at least 2.50 mm long for both cutters.

Step 17 Drawing “Boring Cutter”

Step 18 Use of the Face Plate

Materials: workpiece.

Ø 2.00 steel.

Equipment, Tools: face plate.

DeltaCad drawings.

centering stick.

optical scope.

hammering stick (Ø 2.00 steel).

watchmaker’s hammer.

calculator.

loupe.

Teaching Time: 60 minutes Practical Class Time: 60 minutes Assign reading in Moltrecht for theory and use of a face plate: - Moltrecht I, pages 294 – 310.

Discuss pertinent theory: lesson plan “Face Plate.odt” Have students analyze, then use a face plate: lesson plan “Face Plate.odt” Distribute centering drawings: “centering stick 1.dc” and “centering stick 2.dc” “optical centering 1.dc” and optical centering 2.dc” Perform a demo at a student’s bench: - centering stick first, then optical scope.

lesson plan “face plate.odt.” Have students set up face plate to center the balance hole.

Step 19 Forming the Gear Train Holes and Recesses

Materials: Equipment, Tools: Teaching Time: 20 minutes (communicate general procedures).

Practical Class Time: discussion only Communicate the general procedures for all holes and recesses: - have cutter height arranged before installing face plate.

- position workpiece and mainplate according to the drawing, as closely centered by eye as possible.

- tighten jaw thumb screws finger-tip tight.

- center on reference hole in the mainplate via either the centering stick or optical scope, or both.

- when centering is nearly done, tighten thumb screws as tight as possible with fingers, and perform last adjustments while in this state.

- if any adjustments are made to the thumb screws, always recheck centering.

- if the mainplate tilts away from the workpiece, secure it with rub-off or a clip.

- remove the mainplate after centering is complete.

- turn on lathe, form centered dimple with a graver.

- drill hole as specified.

- cut recess as specified.

- bore open hole as specified.

- the difference between the drilled hole size and the bored hole size is sufficient to account for dimple or drilling errors.

Step 20 Forming the Balance Hole and Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.80 drill bit.

2 cutters.

loupe.

Teaching Time: 5 minutes (communicate technical parameters).

Practical Class Time: 2-3 hours.

Distribute drawing “Balance Wheel Centering” - position the workpiece and face plate jaws as depicted.

ask to see everyone’s centering after this first attempt.

Plan for extra time as this is the first attempt.

Parameters: - drilled hole: - bored hole: - broached hole: - recess depth: recess Ø: Ø 1.80

Ø 2.30

Ø 2.45 (later) 1.12

Ø 14.40

Step 20 Drawing “Balance Wheel Centering”

Step 21 Forming the Escape Wheel Hole and Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.20 drill bit.

2 cutters.

loupe.

Teaching Time: 5 minutes Practical Class Time: 2 hours.

Distribute drawing “Escape Wheel Centering” - if the centering stick is used, remove the jewel.

- position workpiece and face plate jaws as depicted.

Parameters: - drilled hole: - bored hole: - reamed hole: - recess depth: - recess dia: Ø 1.20

Ø 1.70

Ø 1.79 (later) 1.28

Ø 5.00

Step 21 Drawing “Escape Wheel Centering”

Step 22 Forming the Fourth Wheel Hole and Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.40 drill bit.

2 cutters.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Distribute drawing “Gear Train Recesses”: - discuss why recess diameter will be changed.

Distribute drawing “Fourth Wheel Centering”: - if the centering stick Is used, remove the jewel.

- position workpiece and face plate jaws as depicted.

Parameters: - drilled hole: - bored hole: - reamed hole: - recess depth: - recess dia: Ø 1.40

Ø 1.90

Ø 1.99 (later) 1.33

Ø 10.80

Step 22 Drawing “Gear Train Recesses”

original diameter of 4th wheel recess.

new diameter of 4th wheel recess.

Enlarging the diameter of the 4th wheel recess: 1) eliminates the difficulty of using the graver to form the drilling dimple for the 3rd wheel (wall of 4th wheel recess, at original size, bisects centering point for 3rd wheel hole).

2) eliminates the protruberance of brass that would otherwise hang down from the underside of the bridge.

Step 22 Drawing “Fourth Wheel Centering”

Step 23 Forming the Third Wheel Hole and Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.40 drill bit.

2 cutters.

loupe.

Teaching Time: 5 minutes Practical Class Time: 2 hours.

Distribute drawing “Third Wheel Centering” - if the centering stick is used, remove the jewel.

- position workpiece and face plate jaws as depicted.

Parameters: - drilled hole: - bored hole: - reamed hole: - recess depth: - recess dia: Ø 1.40

Ø 1.90

Ø 1.99 (later) 1.28

Ø 9.00

Step 23 Drawing “Third Wheel Centering”

Step 24 Forming the Center Wheel Hole and Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.60 drill bit.

2 cutters.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Distribute drawing “Center Wheel Centering” - position workpiece and face plate jaws as depicted.

The center wheel recess has two depths, two diameters: - the smaller recess/diameter allows for more axial jewel positioning.

- the larger recess/diameter allows for more center wheel clearance to the bridge.

Parameters: - drilled hole: - bored hole: - reamed hole: - smaller recess depth: - larger recess depth: - smaller recess dia: - larger recess dia: Ø 1.60

Ø 2.10

Ø 2.19 (later) 1.27

1.32

Ø 4.00

Ø 12.80

Step 24 Drawing “Center Wheel Centering”

Step 25 Forming the Barrel Arbor Hole and Barrel Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

graver.

Ø 1.60 drill bit.

2 cutters.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Distribute drawing “Barrel Centering” - position workpiece and face plate jaws as depicted.

The barrel recess has two depths, two diameters: - the smaller recess/diameter defines the barrel arbor endshake.

- the larger recess/diameter allows for more barrel clearance to the bridge.

Parameters: - drilled hole: - bored hole: - broached hole: - smaller recess depth: - larger recess depth: - smaller recess dia: - larger recess dia: Ø 1.60

Ø 2.10

Ø 2.21 (later) .70

.78

Ø 4.00

Ø 17.60

Step 25 Drawing “Barrel Centering”

Step 26 Enlarging the Bored Holes

Materials: workpiece.

Equipment, Tools: Ø 1.79 reamer.

Ø 1.99 reamer.

cutting broaches.

countersink.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Introduce the Seitz tool: - show the accessories.

- show how to install and remove reamers.

- demo.

Open up all holes to final diameter: - there exist reamers in the Seitz jewelling set for the escape, third and fourth wheel holes: escape: Ø 1.79 reamer.

- third: - fourth: Ø 1.99 reamer.

Ø 1.99 reamer.

The balance, center and barrel do not have reamer sizes in the Seitz set; they are broached out: balance: Ø 2.45; cutting broach.

- center: - barrel: Ø 2.19; cutting broach.

Ø 2.21; cutting broach.

Deburr lightly all holes – do not chamfer.

Segment 4: Forming ratchet/crown wheel recesses, modifying the crown wheel

Step 27 Forming the Ratchet Wheel Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick.

optical scope.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Distribute drawing “Ratchet Wheel Centering” - position workpiece and face plate jaws as depicted.

Forming the ratchet wheel recess: - cut the recess to one depth, which is equal to the depth of the main, shallower portion.

- cut the recess deeper by the amount the bridge will be faced off by in the finishing process.

- the recess diameter will be left slightly small.

- the reason for this, is that the application of final surface finish will round off the border between the recess and the top of the bridge. The recess will be re-centered at the last stage (on a jig), the recess diameter will be enlarged to final diameter, the bevel will be cut.

Parameters: - recess depth: - recess diameter: .77

Ø 13.90

Step 27 Drawing “Ratchet Wheel Centering”

Step 28 Forming the Crown Wheel Recess

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

6497 barrel bridge.

optical scope.

loupe.

Teaching Time: 10 minutes Practical Class Time: 2 hours.

Distribute drawing “Crown Wheel Centering” - the 6497 barrel bridge will be fitted to the top of the workpiece via its two steady pins. The steady pin in the workpiece that is near the crown wheel recess will need to be removed in order to fit the barrel bridge.

- one corner may need to be sawed off as depicted.

- position workpiece and face plate jaws as depicted.

- optically center on the diameter of the post.

Forming the crown wheel recess: - the recess needs to be formed by moving the cutter back and forth to either side of the lathe axis in order to form 90º corners on both the outer walls and the post.

- change direction of rotation as required.

- as there is no hole, take shallower depths of cut.

- the recess diameter will be left slightly small for the same reasons as the ratchet wheel recess.

Parameters: - recess depth: - recess diameter: - post height: - post diameter: 1.15

Ø 9.10

.70

Ø 2.00

Step 28 Drawing “Crown Wheel Centering”

Step 29 Discussion of Crown Wheel Design

Materials: DeltaCad drawing Equipment, Tools: Teaching Time: 20 minutes Practical Class Time: discussion only Distribute drawing “Crown Wheel and Recess” The watch movement will have a modified crown wheel: - the crown wheel hole will be enlarged.

- two inner cores will be made.

- the cores raise the crown wheel off the floor, define the radial and axial play, and eliminate the center reverse-thread screw.

there will be two screws, 180º apart, which will secure the cores from the underside of the bridge.

- the screws will be provided and need modification.

- the exposed tips of the screws will be rounded and polished to match the exposed steady pins.

- both cores will be heat treated.

the upper core will receive the ALO² finish.

- the crown wheel will be flat polished.

Step 29 Drawing “Crown Wheel and Recess”

Step 30 Modifying the Crown Wheel

Materials: c. 6497 crown wheel.

round brass larger than Ø 6.70.

DeltaCad drawing.

Equipment, Tools: watchmakers lathe.

graver.

caliper.

loupe.

brass measuring gauge.

fine degussit stone.

Teaching Time: 10 minutes Practical Class Time: 2 hours © 2011 SAWTA Use the large round brass to form a measuring gauge: Ø 6.65 on one side Ø 5.65 on other side As the specified diameters are nearing completion, insert the measuring gauge.

When the gauge slips inside the diameter, stop cutting.

Cut a large bevel on the Ø 6.45

diameter on the top side. This will serve as an oil sink. Bring the bevel to a very fine finish with an oiled, fine degussit stone.

The crown wheel is hard, so prepare cutter and use cutting principles accordingly.

Step 31 Forming the Upper Core

Materials: round steel larger than Ø 6.70. DeltaCad drawing.

Equipment, Tools: watchmakers lathe.

milling attachment.

graver.

caliper.

Ø 2.50 center cutting end mill.

loupe.

Teaching Time: 20 minutes (milling) Practical Class Time: 2 hours

Ø 6.40

Upper Crown Wheel Core .28 ² .60

Ø 2.60 ³ Ø 5.64 ¹ (bottom side)

¹ : this is to fit to the modified crown wheel with freedom but no radial play.

² : this depth is to equal the thickness of the inner crown wheel wall + .02 mm.

³ : this diameter is to be milled.

The mill needs only to be approximately centered to the crown wheel. When the crown wheel is rotated slowly during the milling process, the hole will be concentric to the bearing diameter.

As long as this diameter is close to Ø 2.60, the actual size is not an issue.

It is ideal to mill this while still mounted after turning the underside.

Cut a large bevel on the Ø 6.40

diameter similar in size to the crown wheel bevel. It serves the same purpose; finish it in the same manner.

.88

Step 32 Forming the Lower Core

Materials: round steel larger than Ø 6.70. DeltaCad drawing.

Equipment, Tools: watchmakers lathe.

graver.

caliper.

loupe.

Teaching Time: 5 minutes Practical Class Time: 1 hour

.50

Lower Crown Wheel Core Ø 2.00 ¹ Ø 2.59 ² Ø 6.30

.27

¹ : drill undersized, then bore to ensure centricity. Leave hole diameter slightly undersized in comparison to actual post diameter.

Later, broach hole until core fits to post with freedom but without play.

² : this diameter mates to the hole in the upper core. Have upper core at hand. When close to final diameter, fit upper core to lower core.

When upper core fits to lower core with freedom but no play, stop cutting the diameter.

Step 33 Locating and Forming the Screw Holes

Materials: drilling template.

acetone.

DeltaCad drawing.

Equipment, Tools: Ø .65 drill bit.

Ø .85 drill bit.

drill press.

eye protection.

glue.

M .80 tap.

countersink.

counterbore.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1 hour Distribute drawing “Crown Wheel Screw Holes”: - discuss where the holes are to be located.

Drilling the holes: - the drilling template is a 6497 barrel bridge with the holes located and drilled in the crown wheel recess.

- attach the barrel bridge to the top surface of the workpiece, as with the crown recess centering.

guide the Ø .65 drill bit through the holes, and drill through the workpiece. Deburr the holes.

- remove the drilling template and glue the crown wheel and cores into the recess.

- place the workpiece topside down on a flat piece of brass, with the upper core resting on the brass.

guide the Ø .65 drill bit through the holes in the workpiece, and drill through the cores.

Finishing the holes: - separate the pieces with acetone.

- thread the holes in the upper core with a M .80 tap.

- enlarge the holes in the lower core and the bridge with the Ø .85 drill bit. Deburr the holes.

Step 33 Drawing “Crown Wheel Screw Holes”

1 the sliding pinion recess will be located here and shaped as depicted 3 center point of crown wheel; the screws need to be centered around this axis © 2011 SAWTA 2 between the barrel recess and the sliding pinion recess, there is little room for screws 4 that leaves one set area for a screw between the recesses, with the other 180º opposite

Step 34 Modifying the Screws and Forming their Recesses

Materials: supplied screws (c. 1530, part #7854).

Equipment, Tools: watchmakers lathe.

arkansas stone.

india stone.

optical scope.

faceplate.

counterbore.

polishing lathe, cotton wheel, polishing compound.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1 hour Modifying the screws: clamp very lightly on the threads in a Ø .80

collet and reduce the head diameter to Ø 1.16.

clamp lightly on the head in a Ø 1.20 collet, and shorten the screw to an overall length of 1.97, using the india stone.

- round the tip with the oiled arkansas stone until it has a nice dome, is very smooth, and is 1.95 long.

- select a piece of flat steel that can be held in the hands and held safely to a cotton polishing wheel.

drill two Ø .65 holes in the steel, and cut threads into each hole with a M .80 tap.

- screw the two screws into the plate and tighten.

- polish the rounded tips at the cotton polishing wheel.

Forming the screw recesses: - option 1: optically center on each hole in the face plate and cut a 90º recess that is Ø 1.20 x .45 deep.

- option 2: form a counterbore to cut the recesses to the stated dimensions.

Step 35 Heat Treating, Finishing the Crown Wheel and Cores

Materials: 130 grit ALO² granules.

Equipment, Tools: heat treatment accessories.

granite block.

arkansas stone.

zinc block.

polishing paste, ¼ - ½ micron.

small, fine degussit stone.

Teaching Time: 10 minutes Practical Class Time: 1 hour Heat Treatment: - lap down the top surface of the upper core until: 1) it is flat and of a very fine finish. Use a clean and oiled arkansas stone.

2) it is at its final thickness of .80 mm.

- chamfer the holes on the top side of the upper core.

- harden and temper both cores to straw.

- use anti-scale compound to minimize the time spent on refinishing them.

Finishing: apply the 130 grit ALO² finish to the upper core.

- mount the upper core and refinish the bevel with a fine and oiled degussit stone.

- the upper core is now finished and the lower core may be left as is.

- if after heat treatment there is some binding, mount the crown wheel and remove a small amount of metal from the affected surface.

Polishing: - lightly refinish the crown wheel on the arkansas stone as done with the upper core, until uniform.

- polish the upper surface of the crown wheel on the zinc block with the polishing paste.

Segment 5: Forming the click and click spring recesses

Step 36 Discussion of Click and Click Spring Recesses

Materials: DeltaCad drawing Equipment, Tools: Teaching Time: 20 minutes Practical Class Time: discussion only Distribute drawing “Click and Click Spring Recesses” The recesses will be formed via milling in four stages: 1) click spring recess 1.

2) click spring recess 2.

3) click recess.

- the above three operations will be done sequentially on the same centering jig.

4) click spring recess 3.

- the last recess is done separately on a different centering jig. This is to remove the horn of brass protruding into recess 1.

The milling is designed to be done at the Schaublin 102.

The milling rotational speed is 2000, with belt set to the slowest pulley setting. In general, use very slow feed rates.

Step 36 Drawing “Click and Click Spring Recesses”

Step 37 Preparations Prior to Milling

Materials: workpiece, mainplate.

5 bridge screws.

Ø 1” brass rod.

acetone.

Equipment, Tools: jewelers saw and blade.

lathe with 3-jaw chuck.

glue.

jewelling tool.

deburring tools.

Teaching Time: 10 minutes Practical Class Time: 1 hour.

Reduce outer diameter of workpiece: - saw off irregular shape, cutting as close as possible to traced circle, but not cutting within circle.

using the Ø 1” brass, turn a post that is Ø 2.00 by 2.00 long, and face off the remainder of the brass.

- this post is to fit into the center hole of the mainplate, without the jewel, with no radial play.

- screw the workpiece to the mainplate via the bridge screws, glue the mainplate to the brass jig.

turn the workpiece diameter to Ø 36.65.

- remove from brass jig, remove glue residue.

The mainplate: - remove the center wheel jewel (if installed).

The workpiece: - remove the 3 rd - the 3 rd and 4 th and 4 th wheel jewels (if installed).

wheel holes should be clean, and if chamfered, the chamfers concentric to the hole.

- underside of workpiece deburred so that it seats flush to the mainplate.

Step 38 Forming Click Spring Recess 1

Materials: workpiece, mainplate.

Equipment, Tools: Schaublin 102 with 3-jaw chuck, centering jig, cross slide, milling attachment, worm gear and indexing plate.

DeltaCad drawing.

glue.

Ø .085” center cutting end mill (item #37289808 at MSC – Ø 2.14).

male center.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1-2 hours (per person) There are two options for mounting, prior to cutting: 1) mount the brass jig that was used to turn the outer diameter to Ø 36.65 in the 3-jaw chuck, and adjust it until the center post turns true.

2) if trueness cannot be obtained, form a same brass jig while mounted in the 3-jaw chuck in order to guarantee centricity.

Either way, it is essential that the post of the brass jig is turning true in order to obtain reliable and consistent milling results.

This recess houses the base of the click spring, which will have a centered screw from the underside, screwing into the base.

Distribute drawing “Forming Click Spring Recess 1” for the step-by-step procedure.

Step 38 Drawing “Forming Click Spring Recess 1”

rotate workpiece clockwise when cutting 9, 10, 16 dotted line represents mill positions 11 12 15 13. 14 1) mount centering jig in 3-jaw chuck until post spins true.

2) install male center into mill, position cross slide such that it will not be moved to bed.

3) align male center in mill to post, zero out the y-axis.

4) screw bridge to mainplate, glue mainplate to centering jig.

5) attach worm gear and indexing plate to headstock.

6) using the 100-hole portion of the indexing plate, align the 3rd and 4th wheel holes along the horizontal axis by inserting the male center into the holes.

7) mark with a sharpie the hole the pin is in on the indexing plate.

8) remove male center, install Ø 2.14 center-cutting end mill.

6 90° 3 y-axis zero point 9) keeping the y-axis at its zero point, raise mill over the bridge, then lower until cutter touches, zero out the z-axis.

10) retract x-axis so that mill clears surface of the bridge.

11) lower the z-axis by 2.43 mm.

12) rotate workpiece counter clockwise by 139 holes on the 100-hole portion indexing plate.

13) feed x-axis to the bridge until cutter touches, zero out x-axis.

14) cutting: feed the x-axis into the bridge by .65 mm.

15) cutting: rotate workpiece clock wise by 139 holes.

16) Retract mill from bridge, return to y/z-axis zero point (position after step 10).

Step 39 Forming Click Spring Recess 2

Materials: workpiece, mainplate.

Equipment, Tools: Schaublin 102 with 3-jaw chuck, centering jig, cross slide, milling attachment, worm gear and indexing plate.

DeltaCad drawing.

Ø .085” center cutting end mill (item #37289808 at MSC – Ø 2.14).

male center.

loupe.

Teaching Time: 10 minutes Practical Class Time: 15 minutes (per person) This recess accommodates the spring portion of the click spring.

The recess will be cut .05 mm deeper than the other recesses to help ensure the spring does not rub/scrape against the bridge.

The end of the cut stops short from the original offset amount, which leaves a small amount of brass protruding into the recess.

This serves to anchor the base portion of the click spring so that it does not move, eliminating the need for a positioning pin.

Distribute drawing “Forming Click Spring Recess 2” for the step-by-step procedure.

Step 39 Drawing “Forming Click Spring Recess 2”

rotate workpiece clockwise when cutting 1, 2, 8 3 7 4, 5, 6 1): the mill should be at the y/z-axis zero point (position at last step of recess 1).

2) retract mill on x-axis until it clears the top surface of bridge.

3) rotate workpiece counter clockwise by 824 holes on the 100-hole portion of the indexing plate.

Review step 7 before proceeding.

4) lower cutter on z-axis by .47 mm.

5) feed cutter to x-axis zero point.

6) cutting: feed x-axis into the bridge by .70 mm.

7) cutting: rotate workpiece clockwise by 790 holes on 100 hole portion of the indexing plate.

Mark this location in advance with a sharpie.

8) Retract mill from bridge, return to y/z-axis zero point (position after step 1) in preparation for cutting the click recess.

Step 40 Forming the Click Recess

Materials: workpiece, mainplate.

acetone.

Equipment, Tools: Schaublin 102 with 3-jaw chuck, centering jig, cross slide, milling attachment, worm gear and indexing plate.

DeltaCad drawing.

Ø 0.1” center cutting end mill (item # 37290038 at MSC – Ø 2.54).

male center.

Ø .75 drill bit.

M .90 tap.

small pin vise.

loupe.

Teaching Time: 10 minutes Practical Class Time: 30 minutes (per person) This recess will be formed in 2 passes and houses the click.

It is designed such that when the click recoils, the body of the click will slide toward the milled wall, and the click will bank against the wall.

The shouldered click screw is not designed to be load bearing.

This will later be achieved via the manufacture and shaping of the click.

The hole for the click screw will also be located and formed at the end of this step.

Distribute drawings “Forming the Click Recess, Part 1“ and “Forming the Click Recess, Part 2” for the step-by step procedure.

Step 40 Drawing “Forming the Click Recess, Part 1”

rotate workpiece clockwise when cutting 4,5 1,2 6 1) the mill should be in the y/z-axis zero point in preparation for cutting the click recess (position at step 8 of cutting recess 2).

2) retract x-axis away from work piece enough to switch collet and mill.

3) install Ø 2.54 mill and collet into milling head.

4) raise mill over the work piece, lower z-axis until cutter touches, zero out the z-axis.

5) retract mill away from work piece for sufficient clearance to top surface of the bridge.

6) rotate workpiece counter clockwise by 802 holes on the 100-hole portion of the indexing plate.

See next drawing.

Step 40 Drawing “Forming the Click Recess, Part 2”

rotate workpiece clockwise when cutting 9, 10 12 7, 8, 11 7) lower the z-axis by 2.88 mm.

8) feed the x-axis until cutter touches workpiece; zero out the x-axis.

9) raise the z-axis back to its zero point.

10) feed the x-axis to the work piece by .65 mm.

11) cutting: lower the z-axis by 2.88 mm.

12) cutting: rotate workpiece clockwise by 124 holes on the 100-hole part of indexing plate.

Mark this hole in advance with a sharpie.

14) feed x-axis in, form dimple for location for click screw.

15) retract x-axis, remove workpiece.

removing the workpiece: place place end of a wood stick against back side of mainplate, and with a slight hammer tap, dislodge workpiece.

16) separate workpiece from mainplate, drill click hole, tap the hole to M .90, deburr both sides of hole.

Step 41 Forming Click Spring Recess 3

Materials: 2” brass rod.

workpiece.

centering mainplate.

acetone.

Equipment, Tools: Schaublin 102 with 3-jaw chuck, centering jig.

cross slide, milling attachment, worm gear and indexing plate.

DeltaCad drawing.

Ø .085” center cutting end mill item # 37289808 at MSC – Ø 2.14).

glue.

loupe.

Teaching Time: 10 minutes Practical Class Time: 1 hour (per person) Form a brass jig that will center for this recess out of 2” brass: the center post needs to be Ø 1.02 mm.

- the center post needs to spin true.

A centering mainplate is provided: - it has a newly formed hole which will automatically center for this location (it is by the barrel recess).

- the workpiece must have all steady pins that are in new locations removed.

- all original steady pin locations (4) must have a pin.

This recess allows recesses 1 and 2 to blend into each other, allowing the base portion of the spring to ease into the spring portion via a gradual arc.

Distribute drawing “Click Spring Recess 3 Preparation” for steady pin location information.

Distribute drawings “Forming Click Spring Recess 3, Part 1” And “Forming Click Spring Recess 3, Part 2” for the step-by step procedure.

Step 41 Drawing “Click Spring Recess 3 Preparation”

Step 41 Drawing “Forming Click Spring Recess 3, Part 1”

1) remove worm gear and indexing plate.

2) either make a centering jig with a Ø 1.02 mm post which has a pointed tip, or mount pre-made centering jig in the 3-jaw chuck and adjust until post spins true.

3) re-install worm gear and indexing plate.

4) install male center into mill, align to center tip of post, zero out the y and z-axes.

5) screw workpiece to supplied centering mainplate, glue mainplate to centering jig, ensuring it is seated flush.

6 11 2 (dotted line represents centering post fitting into mainplate, before workpiece is attached) 90° 4 9, 10 12 © 2011 SAWTA 6) using the 100-hole portion of the indexing plate, align the 3rd and 4th wheel holes (as was done for recess 1, step 6.

7) mark with a sharpie the hole the pin is in on the indexing plate.

8) install the Ø 2.14 center-cutting end mill.

9) return the y and z-axes to their zero point (if moved).

10) feed x-axis until cutter touches the surface, zero out the x-axis.

11) raise the z-axis until cutter is above the bridge diameter.

12) rotate the workpiece counter clockwise by 200 holes.

See next drawing.

Step 41 Drawing “Forming Click Spring Recess 3, Part 2”

rotate workpiece clockwise when cutting 13 15 14 at end of cut, mill should fit into recess 1 as depicted 13) feed the x-axis to the work piece by .60 mm.

14) lower the z-axis until diameter of spinning mill barely grazes the surface of the wall that was formed when milling click spring recess 2.

15) cutting: rotate workpiece clockwise by 1433 holes on the 100-hole portion of the indexing plate.

Due to small possible positional errors, it may be safer to stop some holes short, then assess.

One can cut a few holes forward at a time to finish it - the end result is that the cutter ends up in relation to recess 1 as depicted.

Recess 3 should be the same depth as recess 1. Due to this operation being done on a different jig, the recess is cut shallower, then adjusted to final depth.

17) adjust x-axis deeper, as needed, to complete depth of recess 3. When the two recesses blend into each other, the recess is complete.

18) remove workpiece, deburr the exposed edges of all the click and click spring recesses.

The click spring hole will be formed after maling click spring.

Segment 6: Forming the click and click spring

Step 42 Discussion of Click and Click Spring

Materials: DeltaCad drawing Equipment, Tools: Teaching Time: 30+ minutes Practical Class Time: discussion only Distribute drawing “Click and Click Spring”: The click: - it has an elongated hole for recoil.

the diameter of the “head” banks against the milled wall.

- the angle of the beak must be such that when the ratchet wheel unwinds, a tooth contacts this angled surface and draws the click into the teeth.

- the click is to be .50 mm thick.

- the click is hardened and tempered to dark blue.

The click spring: - the base of the click spring is locked into position by the shape of the recess.

the spring must clear the “head” of the click.

- the spring must be under tension on the click beak when the click is at its deepest penetration to the ratchet wheel.

- the hole is located in the middle of the base portion, and the screw fastens from the underside of the bridge, pulling the click spring base tight into its recess.

- the click spring and base is .50 mm thick.

- the width of the spring portion is .20 mm.

- the click spring is hardened and tempered to rich blue.

Step 43 Drawing, “Click and Click Spring”

Step 44 Forming the Click Spring

Step 45 Forming the Click Spring Hole in Bridge

Step 46 Forming the Click

Segment 7: Forming the set lever screw, winding/sliding pinion, winding stem recesses

Step 47 Forming the Set Lever Screw Recess

Materials: workpiece.

Equipment, Tools: staking set.

counterbore.

depth stop.

caliper.

loupe.

Teaching Time: 5 minutes Practical Class Time: 1 hour (depending on availability of counterbores) Cut the depth and diameter for the set lever screw recess: - the axial and radial play of the screw are determined by the mainplate.

- the recess serves to allow the screw to pivot, but it does not affect the axial or radial play.

- since the counterbore for the bridge screw recesses has a pilot diameter of Ø 1.25, it can be used to form this recess.

- the counterbore will make the recess larger, but this is not a concern.

- this will be cut in the staking set in the same manner as the bridge screw recesses.

Step 48 Discussion of the Winding and Sliding Pinion Recesses

Materials: DeltaCad drawings.

Equipment, Tools: Teaching Time: 20 minutes Practical Class Time: discussion only Distribute drawing “Winding, Sliding Pinion Recess Positioning”: - the winding pinion recess is cut before the sliding pinion recess to allow for proper zeroing out of the x-axis.

- the winding stem recess will be cut with the same cutter used for the sliding pinion recess.

- the steady pins need to be removed from a 6497 barrel bridge, and the holes drilled all the way through.

- install steady pins in the workpiece at these two locations.

- the barrel bridge will be attached to the underside of the workpiece, and the cutters will be positioned to the existing recesses. The bridge will then be removed, and the cutter fed into the workpiece to form the recesses.

- depth of cut will be the only cut made.

Parameters: - winding pinion recess depth: - winding stem recess depth: - sliding pinion recess depth: 1.58

.32

.90

Step 48 Drawing “Winding, Sliding Pinion Recess Positioning”

Step 49 Modifying the Winding and Sliding Pinion Cutters

Materials: DeltaCad drawing.

Equipment, Tools: lathe.

hard metal cutter or grinder.

winding pinion cutter: Ø ¼“ x 3/64” keyseat cutter (item # 07006299 at MSC).

sliding pinion cutter: dremel tool bit #198.

caliper.

cutting fluid.

loupe.

Teaching Time: Practical Class Time: 1 – 3 hours (instructor modifies cutters)

Winding Pinion Cutter Modification Sliding Pinion Cutter Modification

Ø 1.70

19.00

Ø 6.50

4.70

2.80

Step 50 Preparations to Forming the Winding/Sliding Pinion Recesses

Materials: scrap flat brass.

workpiece.

6497 barrel bridge.

Equipment, Tools: watchmakers lathe with milling attachment.

stool.

extra pulley belt.

face plate.

centering pin.

indexing pin.

2 male centers.

both cutters.

loupe.

Teaching Time: 10 minutes Practical Class Time: 30 minutes Certain preparations should be done before forming the recesses: - position the mill so that the axis of the mill is perpendicular to the axis of the headstock.

- mount a male center in both the headstock and in the mill.

- align the tips of the centers; zero out the z-axis.

- remove the centers, mount the face plate.

- clamp a scrap piece of flat brass in the jaws.

- position and lock the face plate such that the jaws will not interfere with the cutter reaching the workpiece.

- mount the sliding pinion cutter in the mill.

- make some trial cuts on the flat brass in order to fine-tune the perpendicular alignment of the mill axis to headstock axis.

- criterion: when making a shallow cut, the mill should form a rectangular shape; a shape that is trapezoidal indicates the cutter is not perpendicular.

Note: the motor is typically positioned on a stable stool to accommodate the need of the belt to reach the mill pulley.

- remove the sliding pinion recess cutter, mount the winding pinion recess cutter, get it to spin as true as possible.

- remove the scrap brass, install the workpiece into the face plate with the 6497 barrel bridge attached to the underside.

- if moved prior, return the z-axis to its zero point.

Steps 51 - 53

Materials: workpiece.

6497 barrel bridge.

Equipment, Tools: watchmakers lathe with milling attachment.

stool.

extra pulley belt.

face plate.

centering pin.

indexing pin.

both cutters.

loupe.

Teaching Time: Practical Class Time: winding pinion recess: 1 hour winding stem recess: 15 minutes sliding pinion recess: 30 minutes

Forming the Winding Pinion, Winding Stem and Sliding Pinion Recesses

Distribute drawings for step-by-step procedures: 1) “Forming the Winding Pinion Recess, Part 1”, 2) “Forming the Winding Pinion Recess, Part 2”, 3) “Forming the Winding Stem, Sliding Pinion Recesses”.

Step 51 Drawing “Forming the Winding Pinion Recess, Part 1”

Step 52 Drawing “Forming the Winding Pinion Recess, Part 2”

Step 53 Drawing “Forming the Winding Stem, Sliding Pinion Recesses”

Segment 8: Shaping the bridge, application of final surface finish.

Step 54 Forming the Upper Balance Recesses

Materials: workpiece.

Equipment, Tools: watchmaker’s lathe.

DeltaCad drawing.

face plate.

centering stick, optical scope.

appropriate cutter.

loupe.

Teaching Time: 5 minutes Practical Class Time: 1 hour Distribute drawing “Upper Balance Recesses”: - it is easier to cut these now, because if done after being separated from the ¾ bridge, the balance bridge will flex due to lack of metal support.

- center on existing balance hole.

- cut the recesses to the dimensions specified.

- cut recess 1 first, then cut recess 2.

- recess 1 will eventually become the top of the bridge.

- recess 2 houses the stud ring.

- later, after the pieces are separated, the balance bridge will be secured to the mainplate and faced off to complete it.

- recess diameters (a) and (b) can be a little larger than specified, but recess diameter (c) needs to be Ø 4.26.

Parameters: - recess 1 depth: .39 (from top surface of 2.07 mm workpiece) - recess 1 outer diameter (a): Ø 13.00

- recess 2 depth: .39 (from top surface of 2.07 mm workpiece, or .20 mm deep from recess 1) - recess 2 outer diameter (b): - recess 2 inner diameter (c): Ø 5.46

Ø 4.26

Step 54 Drawing “Upper Balance Recesses”

Step 55 Cutting out the ¾ Bridge

Certain preparations should be done before forming the recesses: - position the mill so that the axis of the mill is perpendicular to the axis of the headstock.

- mount a male center in both the headstock and in the mill.

- align the tips of the centers; zero out the z-axis.

- remove the centers, mount the face plate.

- clamp a scrap piece of flat brass in the jaws.

- position and lock the face plate such that the jaws will not interfere with the cutter reaching the workpiece.

- mount the sliding pinion cutter in the mill.

- make some trial cuts on the flat brass in order to fine-tune the perpendicular alignment of the mill axis to headstock axis.

- criterion: when making a shallow cut, the mill should form a rectangular shape; a shape that is trapezoidal indicates the cutter is not perpendicular.

Note: the motor is typically positioned on a stable stool to accommodate the need of the belt to reach the mill pulley.

- remove the sliding pinion recess cutter, mount the winding pinion recess cutter, get it to spin as true as possible.

- remove the scrap brass, install the workpiece into the face plate with the 6497 barrel bridge attached to the underside.

- if moved prior, return the z-axis to its zero point.