The often overlooked Great wheel bushings

One of the most overlooked areas when overhauling a clock movement seems to be the area of the great wheel, great wheel bushing and mainspring. I base my observations on movements that have previously been overhauled and this area was never addressed even though they showed excessive side to side and up and down movement in both the front and back pivot hole bushings. If this excessive wear is addressed properly with a NEW correct size mainspring and new bushings the movement can and will keep the correct time within 1 minute during the 7 day cycle. Now, I'm assuming the rest of the gear train up to the escape wheel has been properly overhauled as well for it to keep accurate time without any major fluctuations throughout the week. Keeping friction down to a minimum in all bearing surfaces is what we want to accomplish in our overhaul and properly addressing this area will make all the difference in friction reduction letting the great wheel (Ist wheel) release power consistently throughout the week without it getting bound up from a out of round bushing.

When the movement was produced at the factory it had the great wheel bushing pressed into place. This can and probably will cause a problem when using a cutter to enlarge the pivot hole to accept a new busing.  The pressed in bushing from the factory will start to spin as the cutter starts to ream out the great wheel pivot hole bushing. This is not a good thing as it could cause depthing problems (great wheel contact with the second wheel pinion) will either be to shallow or to deep causing the movement to stop running unexpectedly or not at all.  Trust me it can and will make your life miserable if it spins and the center is lost. To prevent this from happening I found the best way is to solder the factory installed pressed in bushing into place. Obviously make sure the surface is clean and free of oil, then apply a drop of "TIX" flux abound the bushing (front not rear of the plate) and heat the opposite side which is the bottom with a torch until the flux starts to bubble, I then use TIX solder and just touch the area where the factory install bushing contacts the plate making sure the solder goes all around the factory installed bushing. Not to much, you want it to hold and look neat afterwards If soldered with care it is hard to tell the bushing has been soldered into place.  After that your can be 95% sure it will not spin when using your cutter, but just in case it is advised to scribe a thin line on the factory installed bushing and plate as a reference point should the bushing spin.  

The second step is polishing the large pivots of the great wheel, I have found these normally hold up well with only minor surface scratches, I personally use a Morgan pivot polishing machine attached to a Sherline lathe to smooth out both the front and rear pivots of the great wheel but the thing here is they must be smooth and parallel before fitting for a new bushing.  The bushing needed are large and manufactured by KWM, Bergeon bushings don't come in a large enough inner diameter for our needs here. I find a assortment consisting of sizes L119 through L128 should take care of all great wheel pivot diameters that where used in American clocks. Next select the proper bushing which in itself can be a challenge, especially for the winding arbor side of the great wheel. I don't use a calliper to measure the pivot diameter because the bushing has to fit over the 4 sided winding arbor to get back to the pivot bearing surface. Often it has been slightly deformed from winding year after year. So the trick is to find a bushing that slips over the winding arbor and yet has a good fit for the winding arbor pivot. I have at times slightly taken down on the lathe the 4 sided winding arbor so the proper bushing could slip over it and back to the pivot. The winding key will still work correctly because we just rounded the corners off ever so slightly. The next step after you determined the proper bushing to use is to carefully center your pivot hole using your Bergeon or KWM bushing tool and ream out the hole using reamer No. 5 which has a reamer diameter of 5.85mm. If you have to use the largest bushing L128 you will need the No 6 reamer 8.64mm cut. Next insert the bushing into your cut hole and push it in. Next remove the plate from your bushing machine and do a test fitting by putting the movement together with the winding arbor, no need to add any other parts at this time. Tighten down all screws that hold the plates together and try spinning the great wheel, There should be no binding at all when the wheel is spinning and the movement is flipped up and down. If there is binding the bushing was probably deformed when pressing the bushing into the bushing hole because your cutter is slightly undersize from usage. I found a quick work around when this occurs. First press out the deformed bushing and throw it away.  Next find a rounding broach that will accept your new busing when pressed on with hand pressure. Put the rounding broach into the lathe and turn it on. Gently file (using a very fine file) the
bushing to cut it slightly undersize, just a few seconds. Try pressing your undersize bushing into the bushing hole and retry. it should press in the hole with pressure but not be deformed from overpressure. Put the movement back together with the great wheel and retry. Remember, if you installed one bushing on the front plate for the winding arbor you most also install one on the back plate/

If you made it this far your almost home free. The next critical step is to install a new mainspring.  Don't think cleaning your old mainspring or trying to stretch it out will make it new again because it WON'T.  If you have new 3/4 x .018"x96" do not use them, they are WAY to strong and should never be used in any clock movement overhaul, PERIOD!!!!! I have found the 3/4"x016"x108 to be the perfect replacement for many clocks that use a mainspring that is 3/4" wide. It won't cause excessive wear and tear on your bushings and provides consist power over a weeks time with its 108" length. The Seth Thomas 89 which is probably the most popular mantel clock movement manufactured by Seth Thomas uses a 3/4"especially which is .001 thicker than the replacement suggested above but works perfectly when a proper overhaul was done.

NEW BUSHING INSTALLED

To test the saddle bushing for wear simply grab one end of the verge while it's attached to the pin that slides through the saddle and notice if it moves back and forth or up and down. Chances are it does which indicates wear. Without this being corrected it is next to impossible to adjust the verge to make proper contact with the escape wheel resulting in a weak pendulum swing and a hard to keep running clock. Before this problem is corrected it is essential a proper over haul has been completed from the great wheel up to and including the escape wheel.
Notice that most of the American clock movements that have the escape wheel and verge outside the movement have a saddle like the one pictured. These saddle bushing usually has a build up of brass around the pivot hole as pictured in the photograph. This makes reducing the diameter of the oblong worn hole rather easy.  The best way I found over the years is to simply  use a vise grips pliers adjusted all the way or almost all the way to the close position.
Then starting at the top of the built up brass that surrounds the pivot hole close the pliers. It should take force to close the pliers otherwise adjust your pliers again and retry. Do this starting at the top of the pivot hole working your way down until your at the bottom. Next try fitting the verge on the pin that holds it to the clock. If it fits on the pin redo again until it doesn't. We want to stretch the brass to a slightly smaller diameter than the pin. Do this for both the front and back pivot holes of the saddle. Now that both holes have been made slightly smaller the next step is to use a rounding broach to enlarge the hole slightly. Don't go overboard, broach a small amount then test for fit. What we want to archive when completed is a saddle that does not bind or have any up and down or side to side play when completed.  When complete you will notice the movement will be easier to set in beat and the beat will be constant with little or no fluctuations.