TR2/3/3A TR3 lower outer trunnion

[Gordo]

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

 

[TR4]

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.

 

[PeterK]

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.

 

[TR3driver]

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.

 

[martx-5]

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.