After repairing the detached mainspring on my clock I am restoring the case, after 6 years there were a few areas of corrosion starting to appear, and not being able to go sailing I thought I would fill in some time doing that and writing this post.
A 3" 8 day clock, often more suitable for small craft than a 6", Signed by Marpro but a Smith's Calibre 51, 1960s? |
For anyone interested in pocket watches my blog of the time is still in existence here and includes pictures and descriptions of a lot of very interesting watches and some information on watch repairs and restoration, much of which is relevant to clocks (click on the faults and repairs tags) . There is also a story about what happened when I became watchmaker to Wonder Women, there was a follow up for the second film with some mods required but I only wrote that up on the Facebook page now deleted,
With the above in mind I'll mainly be saying what not to do with the movement and give more positive guidance on the case and glass.
Warning, this can be a long job! Consider removing the glass (see above) and the bezel from the case, both make life easier but is not essential.
Remove the movement, usually just four screws, and put in a safe place.
For replacement parts, tools and consumables in UK Google Cousins and / or Walsh, at least the former requires you to register as a trade customer so that the distance selling regulations don't apply. A lot of the stuff you find on eBay are sourced from one of these and sold at a mark up.
First the warnings:
Do not mess with the hairspring or balance unless you know what you are doing, in which case there is not much point in reading this post! For some reason people seem to think that they can pull or tweak them, I scrapped dozens of pocket watches after people had done that. Adjusting hairsprings and the escapement is a skilled business, damage it and fixing it will likely cost much more than the clock is worth, if it is possible.The motion work of a centre
seconds clock, the inside is more
complicated. If you do take one
to pieces take photos at every
stage to help you when putting it
back together.- Don't mess with the mainspring, if you take it out of the barrel you won't get it back in without the right tools (and if you did manage it there would probably be big isochronism (*) problems due to twisting of the spring), putting a new one is easier as they come pre-wound ready to slide in, but don't bank on being able to do it, take it to someone who does it for a living.
- If taking the movement to pieces ensure it is full wound down before doing so or you will cause significant damage, to be sure put the key on the arbor, hold it and the movement steady and release the "click" (ratchet) and let the rest of the tension off. Like many operations on watches and clocks you could do with three hands doing this.
- Some more modern marine clocks are plated, abrasives may remove the brass.
- If removing the hands take care, the hour & seconds hands, and perhaps the minute hand are a friction fit, levering against the dial is liable to damage the dial. Ideally use a clock makers removable tool or at least use something to protect the dial. When replacing hands, especially the seconds hand do not push it too far on, that can cause friction and stop the clock or make it run short and / or keep bad time. Counter intuitively an escapement that is underpowered, perhaps due to excessive friction in the movement, often runs fast, this is because the balance develops a very shallow and therefore fast action.
- Repainted hands may look worse than worn but clean ones, the exception might be ones that have badly rusted, in that case remove the rust before making a decision, blueing or blacking (in oil) would often be preferable to paint. The exception is the big, usually red, seconds hand on a centre seconds clock, most I have come across have been in poor condition but come up well with red enamel, remove all rust before painting.
- Do not use clock oil on the escapement (The balance (requires it to be removed so not recommended), lever & escape wheel pivots plus the pallet jewels), a platform escapement is about the same size as a pocket watch escapement and needs a light watch oil, a thicker one will likely gum it up. A light clock oil or a heavier watch oil will be OK on the movement pivots.
- On no account spray a movement with WD40 or similar, I have seen that a number of times on pocket watches. It may work in the short term but it will soon cause problems and the residue is difficult to get off unless you have an ultrasonic cleaner. If you have one that it has been done to it will need taking to pieces (except the mainspring barrel) and everything, including the hair spring, needs to be cleaned with a suitable solvent, preferably in an ultrasonic cleaner.
- Do not over oil anything, it will cause as many problems, if not more, than under oiling. Only a small drop is required on pivots. and perhaps a couple of drops of heavier oil into the barrel for the spring but it the clock is running OK leave the mainspring alone.
- If someone tells you a non running clock is over wound don't listen to them, they don't know what they are talking about. If you over wind a watch or clock the spring, or possibly the "click", breaks and its pretty obviously not wound.
- Don't try and clean the dial unless you are sure it is cleanable, many have ink printed numbers etc., often on paper or paint and one can run into the other, any attempt to clean one of these is likely to be disastrous and will require it to be replaced, also names may be transfer printed and come off with the slightest touch. I bought in a nice Kelvin Hughes clock where someone had tried to clean the dial, it looks good with the modern replacement dial but it would probably looked better with a slightly mucky original, just harder to sell. Replacement pre printed dials are readily available for £4-£5 but you will have to cut out the holes for everything apart from the centre one.
sochronism: In this context the ability of a clock to keep time independent of how close to fully wound it is, there are several ways of controlling it covered on my watch blog here.
Regulating the clock
I have the kit to do this electronically using a computer, without that you will need to run it for 24 hours (perhaps less for the first few runs), note the loss or gain, make an adjustment noting how much you moved it, if lucky there may be a scale. Run for the same length of time, note the error, adjust, note and repeat until it is acceptable. Make the first adjustment(s) fairly significant, if you are lucky it will change from running fast to slow or vice verse you can then estimate how much to move the adjuster back.
Ensure the clock it vertical whilst you do this, it the escapement has a positional error (keeping time differently in different positions), you will be wasting your time doing it face up. Positional errors are not a significant issue with a clock so unlike a watch they would not normally be adjusted for it as it takes time, even with analogue or digital timing machines. Wind it well before each run but try and stop just before it is fully wound, you don't want errors due to isochronism errors.
My Mercer after restoration but with an old main spring will be within a minute or perhaps two after 10 - 14 days, it sometime has a rough time on the bulkhead of Sancerre.
The Glass.
If it is mineral glass and in acceptable condition leave well alone, minor marks can be removed using CeriGlass or similar, you won't be able to properly clean / polish the inside of the bezel but taking it out is a risk. If it is plastic / acrylic it may come out easily which will make cleaning and lacquering easier. If very old plastic it may have turned yellow, in which case replace it.
I would advise not trying to replace with a mineral glass, they are supplied "rough edged", unless you are lucky smoothing that and shaping it to fit the average marine clock bezel can be a non trivial job.
New acrylic glasses are readily available and costs about £9, they are easy to fit and won't break if they come out, but they do scratch and scuff much more easily than glass. To fit, clean out the old glue, mastic or whatever from the bezel, a graver works well, but whatever you use be careful not to slip and scratch the bezel. Fit using a thick weak glue, a strong glue such as an epoxy may cause major problems when it needs replacing again (less of an issue with glass which should last years) and a thin glue may not work on the rough surface of the bezel. There are specialist glues that are UV activated requiring a UV lamp, but G-S Hypo was designed for the job, is cheap and easy to use, just follow the instructions and do not skimp on it.
Cleaning a brass case.
Remove the movement, usually just four screws, and put in a safe place.
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While I was about it, on this clock I replaced the long broken off opening knob, the remains were drilled out and a piece of brass rod press-fitted and glued in place. |
Remove the old lacquer, this is best done with multiple applications of paint stripper, it will save a lot of rubbing. Wire wool will help get partially detached or softened lacquer off whilst rinsing the paint stripper off.
Warning: paint stripper and solvents could interact with the adhesive holding the glass in, so handle with care. Also check that they are OK with plastic, if not remove plastic glasses.
Now for the tedious bit, rubbing down. As ever it is a case of starting with a relatively course abrasive moving towards finer. A 240 grit is probably as course as you want to start with, wet and dry will work but I prefer the "Garryflex" flexible block I used on pocket watch cases, but be warned it sheds "grit" so do the work over an easily cleaned surface or paper.
For odd corners and areas of corrosion a fibreglass "scratch pen" will be a great help.
Wire wool is also useful in odd corners and is my final step in cleaning the case.
Now you need to think about the type of finished you prefer, if a "brushed" finish then keep on with wire wool, if smooth then switch to Brasso, I prefer the liquid over the wads. Jewellers rouge is an alternate but it is so messy I gave up on that years ago.
Ready to degrease. |
Now is a crucial step; degreasing. If this is not done properly the lacquer will not be fully effective and you will be doing it all again very shortly. Best is Acetone but others will do, perhaps white spirit or methylated spirit, the latter is often the cleaner of choice for lacquer brushes so should be a good alternate. Don't skimp or hurry this! From this point on wear clean gloves to handle the case until the last coat of lacquer has dried.
Some people recommend warming the case is an electric oven (which helps dry it) and applying lacquer whilst it is still warm as used to be required for some lacquers. I have not tried this and the instructions with the horological "cold" lacquer I use does not mention this option. As I have just found out, avoid very hot (30C) and humid weather, the finish is not as good.
Apply multiple coats of lacquer, I suggest at least four, salt air is a very hostile environment so the more the better to ensure there are no pin holes or thin areas. If damp gets in through one pin hole in the lacquer in time corrosion will spread under the good lacquer, pushing it off and increasing the rate of spread.
As with varnish and paints more thin layers are generally better than fewer thick ones and make sure the previous coat is fully dry before overcoating, so it is likely to take a week.
With all that work plus the service, parts and the risk a clock would not be restorable, you can probably see why I gave up on buying them in essentially unknown condition at £100 - £150 when there was no ready market for them fettled at £200 - £250 with a years guarantee.
Steel Cases
Some marine clocks have a painted steel case with a brass bezel and base. Treat as above through to degreasing then use a good gloss enamel on the steel part, Hammerite liquid paint will do the job, I have not tried the spray.
My 7" centre seconds clock in a steel and brass case, restored some years ago with multiple coats of Hammerite gloss black on the steel body. |
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