Expert: Martin Meyer - 2/2/2008

Question
QUESTION: I have a Herschede 9 tube clock and another Herschede 5 tube clock that probably could use rebushing on the chime side especially. I have taken many clocks apart over the years for various repairs and cleanings but have never actually bought and installed bushings. I have a Unimat lathe that I am hoping to use if you think that is good enough. Where can I buy bushings and reamers that I can use on the thick plates of a Herschede? Are bronze bushings better than brass? Do you just press them in after using some sort of reamer? Is there a tolerance between the size of the pivot and the ID of the bushing?
Thanks

ANSWER: Hi John,
    Overhauling a Herschede tubular chime clock is a very challenging operation. If you want to attempt it, I would very strongly recommend that you get Steven Conover's "How To Repair Herschede Tubular Clocks".
    There are 3.5mm bushings available from clock supply houses like Timesavers or Merritts Antiques. These will be the correct height for Herschede plates.
    I wouldn't recommend using the Unimat lathe for rebushing. The limitation of its small swing-over-bed will cause you problems with the big Herschede plates. Additionally, mounting the plate vertically and in accurate perpendicularity to the reamer would be a very difficult setup.
    I would recommend simply using a drill press, which is an ideal tool for this job. You can get a set of KWM size reamers, including a chamfering bit and assorted size pushers from those supply houses. There is also a drill press adaptor which mounts in the drill press chuck and will hold the reamers. Next, you need some sort of setup on the drill press table to keep the plates perfectly horizontal. Something as simple as several steel blocks of identical height will work fine. This is because the plates have various screws, pins, etc. and will not lie flat on the table.
    The KWM reamer and bushing method uses reamers very precisely sized about .1mm smaller than the bushings. The pushers will press fit the bushings very securely. It is absolutely critical that the reamer cuts holes precisely perpendicular to the plate.
    The bushings will not fit the pivots with an acceptable tolerance, which is .002" to .004". So you need to select a bushing that is one I.D. too small for the pivot, then hand broach the hole to the correct tolerance with cutting broaches (taking care to retain perpendicularity while broaching), followed by polishing broaches. Sets of these broaches are also available from supply houses.
    Brass versus bronze bushings is a matter of some controversy among clockmakers. In the many repairs that I have done over the years, I have seen wear that is as severe in bronze bushings as in brass. Given the greater difficulty in press-fitting bronze bushings, the much smaller assortment of sizes available, and the fact that the final polishing-broaching work hardens the brass surface, I prefer to stay with brass bushings. But, this is a matter of opinion.

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QUESTION: You used the phrase "The pushers will press fit the bushings very securely" I did not see pushers mentioned anywhere else. What are these and where do you get them?
I have Steven Conovers book. It is pretty good.
I also have a drill press so that is not a problem.
You mentioned that you cannot get bushings that are exactly right for the Herschede and you have to "hand broach" them to the correct tolerance. Where can I buy the correct broaches.
Sorry to be a pain but I would rather ask qustions now than have regrets later.
I have taken these movements apart back in the 70s but have never rebushed one. I have made bushings back in the 70s on the unimat lathe for mantle and wall clocks and even made sleeves for the ends of shafts when pivots were broken but I have never bought bushings nor had any formal training. I used to deal with S. LaRose back then but I guess they are out of business?
Thanks again for your patient advice

Answer
Hi again John,
    KWM style bushing equipment is available from Timesavers (www.timesavers.com). In my printed catalog (I'm not sure if it is the most recent) it is on pages 114 through 119. Make sure that you stick with KWM accessories, as the Bergeon accessories are not compatible.
    The reamers are available in a set or individually. The pushers are listed under "Bushing Tool Accessories." You should have all three sizes of reamers. (You will not need the anvils also listed there for your drill press setup).
    The broaches are listed as "broaches-cutting" and "broaches-smoothing". The KWM style drill press adaptor is also listed in these pages.