Suggestions for a tighter bushing fit ??

Bill V

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Jun 18, 2006
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I frequently run into a movement that has had bushings previously installed, and they are often the same diameter as the replacements I keep in stock. When I have to replace these, a bushing of the same size often does not fit as tightly as I would like, as the hole has been enlarged by the previous installation. I haven't found a source for a slightly oversize bushing, and I really don't want to add in the addition time required to machine special ones.

In the past I have used various fixes that seem to work. I have used a centerpunch to spread the bushing, but this sometimes results in too thin of a bearing surface on the ID of the bushing and too deep of an oil sink. I have used a round nose punch to slightly close the diameter of the hole before installing the bushing, and I have used a large flat punch to slightly "flatten" the bushing, causing the outside diameter to increase slightly.

I was wondering if anyone had any other ideas, suggestions, or recommendations for a process that they use to tighten the fit of a bushing that doens't fit tightly ??

Thanks,

Bill
 

David Robertson

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If you have a lathe, make one the size you need.
 

Chris

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Bill:

What about a "double bushing"? Ream it out and install a much larger bushing than needed, then ream inside that and install the new correct size bushing.

I've done this when I've made a mistake. If, for some reason, after reaming a hole, the bushing falls through, I find the best solution is a double bushing.
 

Patrick R

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Jun 22, 2006
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Bill V
One thing you can do is use an, Round Face Solid Punch, on the side of the oil sink, and have the back side on a hard flat surface. The high polish of the punch, leaves a fine finish in the oil sink, while helping to spread out the new bushing, making it tighter. This way you wont have any prick punch holes that make it look bad. I hope you have an inverting set, if not I would get a set of these punches. I don't use these for closing holes, but since you have a round hole I believe this method will work well for you.
Pat
 

Allan Wolff

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As an alternate method, you could slightly knurl the new bushing. Lay it on it's side and push down on the bushing with the edge of a file while rolling it across the bench. The knurled edge will increase the effective diameter of the bushing.
 

shutterbug

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It's quite possible that the original hole was reamed for KWM bushings and you have Bergeon. They are slightly different sized and you might have to order a few of the common sizes to get a good fit in those cases where it's been reamed bigger than what you have. An alternate (though less desirable) method is to use Loc-Tite around the outside of the bushing. It will hold tight and is completely reversible later.
 

Bill V

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Shutterbug,

I think that you hit the nail on the head.

I pefer to use 3.5mm OD bushings because they usually will remove any of the circular punch pattern around the pivot that was done when the plate was manufatured, and the end result is neat and clean, and similar in apperance to the original look of the plate. I stock mostly the 1.40, as I can bore and ream these to fit just about any pivot in a lot of American movements. I do this because then I know I have a nice clean polished hole for the pivot, and I can control the amount of endshake.

I haven't found this bore size with the 3.5mm OD in the KWM lists, so I have been purchasing Bergeon bronze bushings. I have both KWM and Bergeon reamers, but only a KWM for the 3.5mm size. I have found that sometimes when installing a bushing, I have to tighten it a bit with one of the methods I mentioned above, usually using a light tap with a punch in the oil sink, but they always lock in fine and I have never had any trouble. I attributed this to being a bit careless when reaming, which I do by hand, and never thought to check the sizes. I did check just now, and there is only .001" or less for press fit. The OD of the bushings does vary slightly. I think that I'll have to purchase a Bergeon reamer for this size and see if the fit improves.

As I said, I've never had any trouble tightening these, except when re-bushing. I always thought that this was because the hole was enlarged a bit when punching out the old bushing. Maybe I should ream them out instead, or would I end up with the same result either way ??

One of the methods I listed above was to place the bushing on an aluminum block that I use for a work surface, and then, using a flat punch larger than the bushing, I flatten it slightly. I had never checked the measurements before and after, and I was surprised at what I found. With just a light tap, it gained about .001" in diameter, and with a good hit, it gained about .004". I thought that this was maybe just raising a lip at the edge, so I checked it with calipers as well as the micrometer, and it seems to have increased the thickness around the middle as well.

awolff,

The knurling method also seems like it would serve the purpose well, and I'm going to have to try that and see what the results are.

Patrick,

I also like the idea of using a round punch to spread the bushing. As I said, using a center punch deepens the oil sink and leaves less bearing surface length, and a round punch wouldn't do this. I do have staking set, and I found that it has just what I need. Don't know why I never thought of using a round punch ?? It makes pefect sense.

Great suggestions from all, and thanks to all.

Bill
 

shutterbug

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If you punch them out the opposite direction that they entered from (back to front on entry, so reverse that) the hole should be fine. Reaming is not a bad habit though :)
 

RJSoftware

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Someone once suggested to use a bb or simular sized ball bearing. I wonder how to affix one on the end of a small punch.

Probably drill a smaller diametor hole or dip for the BB to set in, then solder to hold in place.

But actually, a flat smooth punch sounds like the best bet. But that depends on how much your spreading it to fit.

RJ
 

RJSoftware

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Bill V;

Wondering what size staking set you have? Do you know timesavers number?

RJ
 

Jim DeRosier

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RJ

There are some very nice steel punch sets available which have bb or ball bearing type ends in graduated polished sizes. Look for dapping punches. After inserting a bushing into the plate you can use an anvil as a backer and set the bushing from the oil cup side or spread the bushing to look like an original french or german oil cup. Using these will distort the bore of the bushing which is easily broached to fit

Jim DeRosier
 

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