The Construction of a SKELETON Clock

The Construction of a
SKELETON Clock
Michael Dempsey, FNAWCC
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Skeleton Clock Tools
Jeweler’s Saw Frame: 2 dozen, #4/0 saw blades
Bees wax to lubricate the blade during cutting
Leather gloves
Vises: Pin & Bench
Caliper, Scale or ruler
Safety glasses
File card or Suede shoe brush (to clean files)
Files: Shop or Flat Bastard files with handles (files must be
sharp)8” double cut, 8” flat single cut and a 6” round taper
“C” Clamps
Hammer: 4 oz. ball peen hammer
Center punch
Broaches
Set of drills
#3 Center drill
Reamers, 0.250”, 0.188”, 0.125”, 0.094”
Drill press
Jewelers lathe or a Micro Machine lathe with 3 jaw chuck
X-acto knife
Special & Optional Tools
• Depthing tool
• Sawing clamp can be purchased at (www.clockbug.com)
• Center line gauge (www.mscdirect.com) #06410138
Sawing Clamp (cutting table)
Center line gauge
Material List
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Hermle 341-020 movement with an 11cm pendulum
4-40 x 3/16 slotted fillister machine screws, 6 pcs.
3-48 x 1/8 slotted fillister machine screws, 2 pcs.
6-32 x 3/16 slotted fillister machine screws, 6 pcs.
½” dia. brass rod stock, 3” long
¼” dia. brass rod stock, 5” long
1/8” dia. brass rod stock, 4” long
Brass sheet 4” x 6.5” 2pcs.
Brass sheet 4” x 4”, 1 pc
#3 flat washers, 6 pcs
#6 flat washers, 4 pcs
Hands from clock material dealer.
Dome and base from clock material dealer.
Spring pins 1/4”, 2 pcs
Spring pins 3/16”, 3 pcs
Starting the Project
• Cut two pieces of brass, 4” x 6.5” x 0.0625”
• Take care and try not to scratch the brass.
• With a scissors, cut out the “Drawing Template” over sized for the
front and back plates.
• Do not cut these on the line, but leave the line to follow during the
cutting process.
• Clean each brass plate to remove grease or oil and use spray
adhesive on the plates and let the glue become tacky.
• Take the paper templates and carefully mount them to the brass
plates. Be careful to eliminate air pockets and set aside to
completely dry.
• On the front plate, center punch all the pillar post holes, which are
marked in green & red, and the center pivot hole marked in blue.
• On the back plate, center punch the two blue holes for the verge
bridge and the top pillar post marked in green.
Templates Glues to the Plates
Sawing – Preferred Method
• Once the plates are dry, and the holes center
punched it’s time to start sawing.
• This can be done one of two ways, separately is the
preferred method.
• Mount a sawing clamp in a bench vise and secure a
plate in the sawing clamp.
• Start sawing on the outside line. Be sure and regularly
lubricate the blade with wax!
• After the outside is cut, drill a about a ¼” hole in
each of the four plate quadrants and saw out the
insides.
• Similarly, saw out the window for the escape wheel
and verge.
Sawing – Another Method
• The second method would be to saw both plates together.
• Start with the top post hole on the front and back plate.
• Spot drill the top post holes with a center drill, then a #17
drill and then use a 0.188 reamer on each hole.
• Align the two plates and drive in a 3/16” spring pin.
• The front plate cutting template is on the outside and when
the assembly is flipper over the other cutting template is
seen on outside of the back plate.
• Align the plates and clamp them together so they can’t pivot
on the spring pin and center drill, drill, and ream the other
two holes for the ¼” posts.
• Install 3/16” spring pins in these holes.
• The two bottom holes are centered drilled, then a #1 drill,
and reamed with a 0.250 reamer.
• Use a 1/4” spring pin in these two bottom holes.
• This will align both plates and secure them for sawing.
Clamping the Plates to Saw
Sawing Procedure
Sawing Procedure Continued
Pin Plates Together
• If the plates were not pinned together, then drill and
pin them together as described earlier.
• The paper cutting template should be on the outside
of both plates.
• The cutting templates will protect the brass plates
from being scratched during sawing, filing and
testing.
• So do not remove this paper until just before its time
to finish the plates.
• Remember, any scratch put the plates will have to
be removed later with sand paper!
Preparation for Filing
Filing
• Mount the plates in the vise, and take care to protect the
plates from being scratched with the vise jaws.
• Start with double-cut file to remove any high or rough
spots on the plates edges.
• Now use a single cut file to “draw-file” the edges smooth.
• To draw-file, put the handle of a single-cut file in one hand
and the other hand on the end of the file. File
perpendicular and flat to the filing surface.
• Draw filing will keep the edges nice and square.
• The plates were designed with shallow radii so they can be
draw filed using a flat file.
• When all the surfaces are smooth, take a small strip of
different grit wet / dry sandpapers and wrap around the
file to draw-sand to the desired finish.
• When finished, do not remove the spring pins that are
holding the plates together!
Draw-File Process
Draw-Sand Process
Filing Process Continued
Selecting Material for the Posts
• There are a total of eight posts needed for this clock.
– Three ¼” plate posts,
– Two ½” plate posts,
– Three 1/8” dial posts.
• The drawing calls for brass but you can select any material
that you desire.
– Aluminum
– Stainless steel
– Blued steel
• At this point, you may consider the material you will use
for your screws too.
• This is a great place to personalize the clock.
• Take some creative freedom with the shape of these
posts if you wish.
Making the Posts
• After the material is selected, cut to length.
• Use a three jaw chuck and face off the material with either a
cross slide or a graver.
• Find the center and drill to the drawing size specified.
• Tap each hole to the drawing specifications.
• Machine the boss on the end of the post.
• After this step is complete, turn the material around and use
the same procedure on the other end of the post.
• IMPORTANT. All posts must be made to the same length to
prevent the plates from twisting when assembled.
• The post “boss” must fit tightly into the reamed plate holes to
keep the plates properly aligned.
• When complete, do not remove the spring pins that are
holding the plates together!
Cutting the Boss
Checking the Post Length
Drilling the Post
Prepare the Hermle Parts
• Disassemble the Hermle movement and prepare the
parts for the new clock.
• Remove the four lobes from the center star cam /
wheel.
• Inspect all components and make a determination if
any repair is needed.
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Polish pivots carefully not to remove plating
Barrels may need to be bushed
The spring may need to be replaced
Polish the components to match the plate finish
• The motion works & click components may vary
depending on the Hermle version being used, so plan
to improvise here.
• Choose an appropriate pendulum leader and bob.
Wheel Layout Methodology
• Locate the mark for the Center Wheel on the front plate
in the center of the large circle.
• By starting with the center wheel and working up and down
the train, accumulated error will be minimized.
• The drawing shows a reference line in gray which should
give an approximate location for each hole.
• Use a center drill for all pivot holes and make sure it is not
too big for that pivot.
• Start by spot drilling the center hole with a center drill.
• Drill through both plates and leave enough material for
broaching to the proper pivot size.
• Using an Ex-acto knife and a straight edge, scribe a center
line down the middle of the plates, just deep enough to cut
through the paper and lightly scribe the plate.
Vertical Line Scribe
Hole Layout with Depthing Tool
• Start with the center wheel and place it and a mating wheel in
the depthing tool and set the depth so the wheels run smoothly
on their pitch circles.
• With the depthing tool set, mark the wheel centers by lightly
scribing an arc on the plate at the vertical line.
• Repeat making the depthing tool mark for each set of wheels.
• After all your wheels are laid out, center punch and spot drill
with a center drill at each scribed pivot mark.
• Drill through both plates and leave enough material so the hole
can be broach to the proper pivot size.
• With all holes drilled, remove the spring pins.
• Check the pillar posts for proper fit to the plates.
• Broach each pivot hole for proper wheel fit.
• Use a smoothing broach on each pivot hole to work harden hole.
• Use a counter sinking tool to make an oil sink for each hole.
• Check each wheel for end-shake and free spinning.
Depthing to Determine Spacing
Depthing to Locate Hole
Wheel Layout with Center Line Gauge
• Attach a Center
Line Gauge to a
pair of calipers to
mark holes from
drawing
dimensions.
• See last page for
instructions on
how to correct
dimensions for
gauge off-set.
Assembled Plates
Assemble the Click Components
• The click spring, click retainer and click ratchet wheel will be
needed from the old movement.
• These components may vary, so be prepared to improvise.
• Assemble the movement and the ratchet wheel on the winding
arbor.
• Using the click retainer as a template and scribe the hole
location.
• Drill and tap the retainer hole.
• Use the same procedure for locating, drilling and tapping the
click spring and click.
– You may choose to use the old rivet or make your own
– Or make a removable shoulder screw-stud.
– Other click springs are available in supplier catalogs.
Assemble the Motion Works
• You will also need the center–arbor pinion (hourpinion), hour-wheel, intermediate-wheel and post from
the old movement.
• Assemble the hour-pinion and hour-wheel on the
center shaft.
• Locate the intermediate wheel and depth this wheel
by “eye” directly under the center wheel.
• Make your own post or use the one off the old
movement.
• Drill and broach the hole to size to for a press fit.
• Or you may make your own screw in stud.
Click & Motion Works Picture
Drill & Tap Verge Holes
• Locate the two holes on the back plate that mounts
the verge bridge and pendulum post.
• Center punch, center drill, drill and tap according to
the drawing.
Assembly & Test
• Complete the balance of the clock assembly without
the dial.
• Leave the paper template on the front & back plates
to protect the brass.
• Wind the spring.
• Add the suspension spring, pendulum rod and
pendulum bob.
• Set the clock in beat and test for at least a week.
Dial Plate and Posts
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See dial plate and dial drawing
Cut-out and glue the dial template to a piece of brass.
Mark the three holes for the dial posts with a center punch.
Use the same method to saw and file as with the plates.
Make the dial posts according to the drawing.
Center drill, drill and ream the three post holes in the dial and in
the front plate according to the drawing.
• Press the dial posts in the dial, super-glue and file smooth.
• Do not put the dial on the front plate until the plate surfaces
are finished.
• When the clock is complete, the paper dial should be trimmed
with a dial-cutter and glued to the dial plate.
General Surface Finish
• Remove the paper template by soaking the plate in lacquer
thinner.
• The plates can be sanded to the desired finish using
different grit of sand papers on a rigid surface.
• If you where very careful during this process, you can
start with a medium to fine wet / dry sand paper.
• Lay your plates flat on a hard surface and move them up
and down only.
• Sand the length of the plates to create long straight lines
and avoid short swirling actions. Use cotton gloves to
prevent body oils from the plate during the final sanding
process.
• Would not suggest using any type of power buffer on
these plates which could damage them beyond repair.
Surface finish
Lacquer or Wax Finish
• This operation is totally up to the individual, but clean the brass
surface with a clean-drying solvent before finishing.
• The “wax finish” is preferred by many over a high gloss shinny
finish. It gives the clock an “older look”.
• Wax the plates, posts, and the dial plate except the front of
the plate using a high grade automotive wax.
• Do not wax the front of the dial pan. You could have problems
gluing on the paper dial to a waxed surface.
• Let the wax dry and hand buff with a cotton cloth.
• As an alternative to wax, lacquering the clock will give you a
finish that will last for a very long time.
• Use a high grade automotive lacquer and lacquer thinner, mix
them in a gallon can, 80 percent thinner to 20 percent lacquer.
• Once mixed, put toothpicks in all pivot holes and dip parts into
the container and hang them to dry. They will dry very quickly.
Final Assembly of the Clock
• Cut out the dial with a dial cutter slightly larger then needed.
• There is a small notch at the top of the dial pan to use as a
reference point for the “12”.
• Glue the dial to the pan using rubber cement lining it up by
eye.
• Use an X-acto knife to trim the edges when the dial is dry.
• Very lightly spray clear lacquer over the paper dial.
• Push the dial pan onto the front plate holes.
• The dial is held on with by the friction fit into the holes.
• Assemble the clock, attach hands and pendulum.
• The clock is finished and ready to enjoy
• The clock was designed to fit under a standard dome and
base that is available from many of the clock material
dealers.
The Finished Clock
• You can add variations
– Blue steel screws
– Brass screws
– Silver dial plate
– Engraved dial
– Passing strike on bell
– Decorative posts
– Decorative pendulum