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TR2/3/3A TR3 lower outer trunnion

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G

Gordo

Jedi Hopeful
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OK guys, I've rebushed the lower outer arms and have new trunnions. I've found the end play in the book. I know the new bushes need to be reamed/honed to fit the new trunnion.

What I can't seem to find is the clearance between the bush and trunnion. I don't want to go too loose or tight.

Any suggestions?

Gordo
 
When I took mine to the machine shop, they asked if I wanted a slide fit and they came back perfect. Arms slid on the trunnions with no play and rotated smoothly.
 
It's OK to leave the bushings a little large (tight). The bronze trunnion is soft enough so when it rotates against the reamed steel bush, it will wear-in to a perfect matched fit.

Just leave a couple of thousands clearance. If you are using an adjustable hand reamer (I did), stop as soon as you reach a fit. Most likely that will be the best tolerance with a hand reamer that you will get.

So don't set them too loose, nice and smooth.
 
The trunnion pin has the clearance built into it. Ream the bushings to the standard size (can't recall offhand if it's 5/8" or 11/16") and they will fit just fine. Enco is one source of inexpensive fixed reamers (and where I got the one I used for my trunnion bushings).

FWIW, Personally, I don't like adjustable reamers. I find it almost impossible to get a good surface finish with them; and they sometimes dig in and ruin the work. Expansion reamers work well, but are expensive to buy new.
 
The size is 5/8" (0.625). As far as adjustable reamers go, the ones available now do not come with a cone shaped guide that is used to keep the reamer properly aligned. I have an old set that my father gave me that has these guides and they do a beautiful job of reaming. The other problem that people run into when using adjustable reamers is to try and take too much material out at one time. When I did my trunnions, it took three passes to get a perfect fit.
 
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