Clock repair blog

SETH THOMAS SONORA CHIME

This clock has two mechanisms. The one closest to the front of the clock powers
the strike and the time gear trains. It also trips the chime. The chime mechanism is
closest to the back of the clock. The chime mechanism has a huge mainspring and mainspring
barrel. Pay very close attention to the teeth on this barrel; if this mainspring or
barrel lets go , it will do much damage th the mechanism and possibly to someone’s finger.
Most of these clocks are not self correcting on the chime or the strike.The
mechanism that runs the strike and the time is very similar to the 8 day
time and strike american
clock mechanisms. The chime usually is sounded on a row of bells mounted above
a resonating box. These clocks have a beautiful sound in my opinion. The hammer
sequence is different on these clocks than on the modern German w/c self correcting
mechanisms.
The time and strike mechanism is activated by the chime mechanism ,
however ,the chime mechanism is activated by the trip lever and the trip cam in the
time and strike mechanism. Be absolutely sure to check the ratchet dog system on
the chime mechanism; I have seen many of these loose when they come in for repair.
If one of these lets go , the results will be disastrous indeed. There is usually
a pin on the inside of the ratchet that the click spring pushes on to make the click
work. Be sure to check this pin very carefully , it must not be loose , or the
ratchet system will fail.
The pendulum on these mechanisms usually will have at lease 2 inches of
swing, and the pendulum bob is one of the heavier (2 ¾ ounces typically) types.
Before getting too far on the repair of one of these clocks . it is very wise to check
the gear teeth on the chime mainspring barrel. If the barrel is bad , there is no point
in doing the rest of the work until the barrel problem can be resolved. If the chime
mechanism won’t work , then neither will the strike . The hammer throw is critical
on these clocks ; it may have to be reduced if it has been tampered with . Take the
hammer =assembly out , take it apart and clean it thoroughly. I have frequently seen
these mechanisms bind up because of excessive hammer friction due to too much
throw or gummy oil.
The hammer sequence on this mechanism is different than usual. It is as
follows: looking in the back of the clock and assigning numbers to the four bells
used for the quarter hour melody starting with the bell closest to the back door
and calling it #1 and the one next to it #2 ,Then #3 and finally #4 , not counting the
bell used for the hour strike or course , the order for the quarter hour chime (down
the scale westminster) is ; 2 ,4 ,1 ,3 . This same sequence would also apply to the
3rd measure of the ¾ hour chime.

SETH THOMAS CLOCKS

The Seth Thomas clock company has made millions of clocks, many of which have 2
mainsprings , two gear trains ,and one count wheel. Most of these types of mechanism
have a wire lock arm system which usually consists of two small shafts with wires
attached
to trip the strike in conjunction with the count wheel. The bushings for the
lock arms are critical. They must be loose , but not too loose. Any thing over
about.006in maximum play. Oil in this area will probably cause problems;
unless the shutoff wire has a return spring.
If the actual shutoff wire has a return spring , it may forgive some slop however ,be
careful, and be sure to check the operation of the wire very carefully. The slop in the
bushing will cause sideways movement of the arm and may be enough to disrupt the action
between the shutoff lever and the count wheel. The slot in the count wheel that the flat
wire end drops into is not very wide.
Another part of the strike system that is critical is the lift cam attached to
the
centerpost. This cam is almost always press-fit. It must be tight enough so
that it cannot be moved by even the strongest hand. If this cam is soldered, beware,
this almost always means that it has either come loose , or someone didn’t know
what they were doing. The lever hooked to the count arm that works with this cam must
contact that cam at the center of both the cam and the lever. PICTURE. If the cam
does not have a beveled edge , then the minute hand should not be turned backwards.
If the cam has a beveled edge , then counter clockwise motion is probably an option.
The lever will usually gave an angled edge so that it will spring back out or the way
of the cam when it moves counterclockwise.
All of the levers that are hooked into the count arm axles must be absolutely
tight. They must not be able to move under normal operating conditions. It is not
necessary to solder these parts to make them stay put. However if they gave been damaged,
as a last resort from a practical standpoint, soldering may be the only option. Remember
to use only enough solder to do the job. Again, let me stress, be absolutely certain that
all the flux is removed when the job is done before the clock is reassembled.
Many of these clocks have escape wheels with somewhat long fine teeth. Be
careful , they bend very easily. The Dead Beat type of escapement is common on this
type of mechanism. Be aware of this and keep in mind that the tolerance of the bushings
certain nothing moves when you do (except the set screw , of course!) . Be absolutely
certain that the hour tube still has endshake after this cam is secured. Now move
your attention to the back plate. There is a cam friction fit on the back of the
centerpost that needs to push the hammer lift assembly out (via the swivel lever
on the back plate) far enough to clear the indexing pin so the hammer lift assembly
is in position to lift the hammers that will sound the quarter hour chime after the trip
lever releases. On the hour this cam must just be starting to lift the swivel lever in
order for the hammer lift assembly to be in the correct position when the quarter
hour chime starts. This mechanism can take as long a 1 and a quarter hours to self
corr
certain nothing moves when you do (except the set screw , of course!) . Be absolutely
certain that the hour tube still has endshake after this cam is secured. Now move
your attention to the back plate. There is a cam friction fit on the back of the
centerpost that needs to push the hammer lift assembly out (via the swivel lever
on the back plate) far enough to clear the indexing pin so the hammer lift assembly
is in position to lift the hammers that will sound the quarter hour chime after the trip
lever releases. On the hour this cam must just be starting to lift the swivel lever in
order for the hammer lift assembly to be in the correct position when the quarter
hour chime starts. This mechanism can take as long a 1 and a quarter hours to self
corr on the escape wheel and the verge are critical if the clock is to keep good time. If the
verge is located on the front or back outside of the plate; it still must not have sloppy
bushings.
Always check for worn main wheel gear teeth, and worn pinions (wire pinions
can be replaced of course) these two situations will cause stoppage and timekeeping
problems. Also check for bent gear teeth ;even slightly bent teeth can
cause the clock to stop.

The seth Thomas Adamatine clock regulator: 1 turn is 2 min
in 24 hours. The mainsprings in these clocks are of the standard .018in. by .750in. by 96in.
american manufacture. They must be thoroughly cleaned and all the old oil must
be removed without scoring the spring. They must be unwound ;opened up entirely
and all the surface cleaned by other than an ultrasonic cleaning machine. The ultrasonic
can and probably should be the first cleaning step. There are in fact some movements
that don’t take the standard size spring so be sure to measure the springs carefully. A
sticky or fatigued mainspring can cause the clock to stop erratically , and or not keep
time. Problems with the strike will also be experienced; such as sequence getting off
and or the speed or the strike varying.
Some of these mechanisms will have a return spring on the shutoff, and some
will not. Care must be taken to insure that the strength of the return spring is not
strong enough to make the clock stop. Also make sure that the surface of the trip cam is
not rough enough to add enough friction to stop the time gear train. The cam lift surface
must be smooth.
I have found that cleaning mainsprings with an abrasive substance such as
sandpaper is ok as long as the spring surface is not scratched excessively. If the
surface of the spring is scratched, then friction will be added in direct proportion
to the extent of the scratches , quite possibly more than the old oil that was removed
by the substance in the first place. A self defeating situation at best!! Use fine steel
wool with cleaning solvent to remove the old oil. The old oil will often look like a
yellowish brown stain and can be mistaken for the color of the steel if you are not
aware of this. Some springs do have this color; so check if the stain can be removed
by fine steel wool and solvent, it is probably not the steel color!

REPIVOTING:

Repivoting skills are a must. The only way to become proficient at this is
practice; lots of practice. Accuracy to within .001in. Is absolutely necessary if
repivoting jobs in clock repair are to be done properly. With the piece in the lathe,
perfectly centered, bring the point of the graver SLOWLY to the center of the work as
it is spinning. In the instant before the end of the graver contacts the end of the
spinning stock, holding your breath is a good way to steady your touch . Of course,
using the steady rest as a solid anchor for the graver is a must. In order to make the
stock end true center visable; square off the end with a file as it is spinning in the
lathe. The resulting circular pattern will appear to come to a point; the point is the
true center of the spinning stock. If the true center is struck, there will be a cone
shaped indentation in the end of the stock. If there is a tiny protruding dimple in
the middle of the cone , then center has not been properly struck. You will have to start
over with a flat surface again. You must either have exceptional vision, or learn to use
a magnifier. A sharp graver is needed. continue to practice striking center and avoid the
small dimple in the middle. When you drill the stock go slowly and use a pivot drill
whenever possible. The hole that is drilled should be about .001in. smaller than the
stock you intend to use. This is true for most repivoting work in clocks on straight
shafts larger than .020in.. Use the lathe and wire chucks to install (drive in( the new
pivot. It should not be necessary to
strike the pivot end very hard to get the pivot to seat properly. If possible the hole
for the pivot should be twice as deep as the pivot is long. This is not always possible,
however. If you are drilling into a shaft that has a gear over where the pivot is located ;
;be very careful not to drill into the gear so as to weaken it. Check this out in advance.
In order to drill hard steel properly , you will have to draw the temper on it do the
work, and then re-temper the piece when you are done (before you install the new
pivot(. This is the correct way to fix a bad pivot in almost all cases. Repivoting may
seem impossible when you first start ; but it will get easier with practice. There will
indeed be times when it may not be practical to repivot. For example : a french clock
with the pinion gear as an integral part of the shaft with a bad pivot in the opposite
ind: the shaft will be very hard steel , and it will be very difficult to strike center.
This principal of repivoting applies to more than just repivoting.

BUSHINGS:

Bronze bushings will outlast brass in most cases. Be sure to check for wear
that does not show: that is , wear underneath the oil cup. Before pressing in a new
bushing be absolutely sure that the hole is re-centered. PICTURE Reamers are
available that will make a hole just the right size for the bushing to be press-fit into
the plate. I have always used a micrometer to measure the pivot sizes and it
seems to work just fine. Remember that when a bushing is pressed into the brass
plate, the hole in the center of the bushing will be squeezed to a smaller size, Between
.001 and .002 is common. Keep this in mind when choosing the bushing size for the
pivot.Relocating a worn bushing to its true center is difficult and must be done
carefully. Before disassembling the mechanism, after cleaning it, check each bushing
to find out how much wear has occurred. The bushings that are worn should be
marked, if necessary , and the amount and direction of wear should be noted , by
a mark on the plate with a non-permanent marking pen with an extremely fine point.
I have used a small round taper file to back file the bushings to their original center.
Do this by filing back as far as they have worn.Use a drill bit to open up the hole
before using the reamer on it.

In my opinion ultrasonic cleaning machines are the best way to clean clock
mechanisms, if it is understood how they work, and what they do to metal. If petroleum
based cleaners are to be used , it is absolutely imperative to remember the following
information: The brass and steel metal in clocks has microscopic holes that the oil will
fill and hold a thin film on top. When the clock mechanisms are run through the
ultrasonic cleaner ; all the oil even the oil that is imbedded in the pores of the metal
is removed. When the surface is re-oiled the new oil will often be soaked up and the
result is the same as if the part had not even been oiled in the first place. Disassembly
is a must. It is not possible , in my opinion , to properly clean a clock mechanism
without disassembling it totally. It is best to use a cleaner and a rinse in separate
containers preferably 2 separate cleaning machines at a minimum. The ultrasonic
machines work by actually vibrating the liquid at about 15,000 hertz forming small
bubbles that effectively scrub the objects in the tank clean.
Water based cleaners: Often it will be necessary to use water based cleaners.
Be absolutely certain that all the moisture is removed from the mechanism before
re-assembly and if a dryer is used be aware that plastic parts will melt! I have seen
many clocks that have been destroyed by rust. Avoid using substances that are extremely
caustic or acidic , they may do a great job of cleaning the mechanism and make look
shiny and bright , but the steel parts will most certainly rust later and if this rust
is not removed , the mechanism will be destroyed.
Another way to clean is to use a tooth pick on the pivot holes. This takes
a long time , and is very tedious, but sometimes it is the only way to get the thing
cleaned. A small amount of cleaning solvent on the end of the tooth pick will make
it a faster operation. Twisting the toothpick slowly by hand probably is the best
way to insure that the pick wont break off in the hole. I find it necessary to use a
magnifier to check the Inside of the bushing to determine when it is clean.

I have found that cleaning mainsprings with an abrasive substance such as
sandpaper is ok as long as the spring surface is not scratched excessively. If the
surface of the spring is scratched, then friction will be added in direct proportion
to the extent of the scratches , quite possibly more than the old oil that was removed
by the substance in the first place. A self defeating situation at best!! Use fine steel
wool with cleaning solvent to remove the old oil. The old oil will often look like a
yellowish brown stain and can be mistaken for the color of the steel if you are not
aware of this. Some springs do have this color; so check if the stain can be removed
by fine steel wool and solvent, it is probably not the steel color!

METALS:

Brass: Brass is an alloy of copper, lead, tin, and zinc. If brass gets hot it will
get softer according to how hot it gets. It is important to remember this when soldering
brass parts ; do not get them too hot or they will be ruined. How hot is too hot? Hot
enough to melt lead solder is ok, generally speaking. If you are going to try silver solder
be careful. much over 450 degrees F and you will probably make the part that you are trying
to fix useless. the bottom line here is : if at all possible do not solder ; use it as a
last resort. BE ABSOLUTELY SURE THAT ALL THE FLUX IS REMOVED OR THE PART WILL BE DAMAGED,
PROBABLY BEYOND REPAIR.
To make brass harder , it must be struck , preferably with a smooth hammer
while the piece that is being worked is resting on an anvil . The longer and harder it is
worked the harder it will get. For example , it is possible to make a click spring out of
soft brass by hammering on it and shaping it.
Use hard steel to repivot; it is available through almost every
supplier. I recommend using drill rod to make levers and shafts; it can be hardened if
desired and is relatively easy to work with.
A tool for installing click springs can be made by cutting a narrow slit in the end
of a piece of drill rod just wide enough for the spring and deep enough to hold it.
Harden the end and you will be able to install just about any friction fit click spring.
Remember to use a hole closing punch on the holes before installing the spring so it
will be tight.
Round ended punches ; small ,medium, and large will be ;needed . Two punches
for straightening gear teeth are a must if any work with bent gear teeth is to be done
.PICTURE. The end should be hardened and the edge should be as sharp as possible.
CLEANING