Fit of steel elevator bushings in bronze bearings

[FoxTrotter]

I've recently started a 7SS build and am about to assemble the 11060 bushing into the 93021 bearings (which are already installed). The manual says that if the 11060s don't fit into the 93021s (and they don't begin to fit), sand them down. My question: what kind of fit am I striving for? Should the 11060s fit tightly in the 93021s, or sufficiently loosely that they can easily be rotated after insertion?


Thanks!


Michael

[aviator79]

The ideal is frictionless rotation with no noticable diametral play. It took me a lot of work chucking up the steel bushings in my drill press to get them all to work.

Also, press the bronze bearings into the elevator before sanding the bushings. When the bearings are pressed in, the ID will compress some, so if you had the steel fit perfectly before pressing, it will be too tight after, and you'll be back to sanding.

[FoxTrotter]

I've spent some while using 180 (followed by 220 and 400) grit sandpaper on the steel bushings, with no noticeable progress. Bronze is a lot easier to work. Is reaming the bronze bearing a viable option?


Thanks


Michael

[aviator79]

How are you sanding them? Chucking up in a drill press? It did take me some time and many, many iterations. Change your sandpaper frequently, With patience you will get there. I think reaming the bronze accurately would be more difficult. You definitely don't want them too loose or off-center.

[FoxTrotter]

Yes, chucked up in a drill press.

[Shadowrider]

For me, this was a frustrating part of the build so far. Not sure if you have ever flown a plane with worn out control surface "bearings" but the controls chatter and feel super loose, so don't sand to much. Like others have said, spend a lot of time sanding these until they move freely, but have no play. Took me a couple full days doing this until they are right. I am sure it will pay off down the road so you don't have stiff controls.