Expert: Martin Meyer - 6/10/2007

Question
QUESTION: I have an older Franz-Hermle mantle clock (1982 I believe) that my Grandfather owned. He was proficient in some types of clock repair but never got around to fixing this one before his death. My Grandma said she believes it may have been overwound for years.

The movement is an M8, Model number 520, F-H manufacturer part number 340-020.

Per some instructions online I've tried restarting the clock with the 1/4 turn of the wheel. It goes for a few seconds and then loses momentum and stops. If you move the clock hands manually, the chimes will sound accordingly.

Is there an "at home" way I can check to see if the clock has been overwound or any other common problem that I can resolve on my own (I have several clock reference manuals around somewhere but they're for cuckoo clocks)?

Any help would be appreciated. My Grandmother loved the sound of the clock and would love it if it could run again. Thank you.

ANSWER: Hi John,
Your clock has a Hermle "floating balance" movement. these movements often wear out in about 15 years, and either that, need of lubrication, or accumulated dirt and dried oil are your most likely suspects. Don't worry about "overwinding"; that term is probably the most common misconception about clock repair, and there really is no such thing as overwinding.
    I would start with lubricating the movement. Put a small drop of clock oil (no other kind of oil!) at each point where a gear shaft goes through the front or back main plates that hold the whole movement together.  This is about all you can do, short of overhauling or replacing the entire movement.
    I recently answered a question, "How do you regulate this clock?" (and a follow up also). This related to the same type of clock as you have. Please take a look at that answer for more detailed information on the floating balance escapement, which you may find helpful.
    I hope this information is helpful. Thanks for your question.  Martin

---------- FOLLOW-UP ----------

QUESTION: Martin,
I looked through all of my Grandfather's clock supplies and found what I believe was his clock oil (green liquid in a plastic "bulb" with a long metal tube and small tip) but I won't use it as I'm not sure. Do you have any recommendations as to a brand of oil and/or what some may cost? I'm going to invest in it to hopefully get this clock working and I'm thinking of taking up the hobby as he has a lot of parts and clocks laying around that he wanted to get working.

Also, do you know an average cost of what an overhaul or movement replacement may cost?

Thanks again, John.

Answer
Hi again John,
    The container sounds like clock oil, but clock oil should not be green.  At any rate, clock oil deteriorates with age and old oil should not be used. There is a huge range of varieties and prices of clock oil. Synthetic oil has mostly replaced natural (mineral, fish and whale) oils, and I would recommend a synthetic oil. Nye and La Perle oils are well-established standard oils. You can get (Prices Approximate!) a pint of La Perle oil for about $61, an ounce of Nye oil for about $7, or 4 ml. of Etsyntha 859 for under $20. By the way, for the Etsyntha, that's over $135 an ounce! There is also some anecdotal evidence that some clock oils are incompatible with others, resulting in big problems when re-oiling a movement. Personally, I find it difficult to justify top-of-the-line prices in most cases. I have used numerous different clock oils and haven't really had any problems. Nye clock oil is a synthetic, not expensive, and I have personally had good results with it. The key qualities of clock oil that distinguishes it from other lubricants are that it is non-spreading, non-drying and non-oxidizing. Clock oil is one of many areas in clock repair in which everyone has a different opinion, so I would give a couple a try and go from there.
    Thanks again, Martin