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TR2/3/3A TR3 Wishbone bush ream spec?

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K

karls59tr

Obi Wan
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Just had one set of wishbone bushes pressed in and reamedat a machine shop Told them to ream 5/8"(.625) Turns out they are .630! How critical is this spec? Using aftermarket trunnion. I should have miked the trunnion first I guess.
 
I don't think .005" will hurt much; but I would consider it a signficant portion of the bushing's life. If you told them .625" but they reamed to .630", they should pay for new bushings and redoing the work they did wrong.

Being a poor tool freak myself, I bought a $15 reamer from Enco and turned a mandrel using a drill press and sharpened file; so I could skip the machine shop.
 
The guy who reamed mine thought they should be a very snug fit and only gave me about .001" clearance. He said, "They'll loosen up soon enough." My new trunions were undersize, about .6235". I think the bushes were meant to go to .625". If your trunion spindles are like mine, I think you've overshot the mark a bit.

I also brought 'em in and said, "Ream 'em to .6250"." He said, "Bring me the part they fit onto, and let me be the judge." So I did, even though I trust my mic and my ability to use it. It's probably always a good idea to bring in the mating part. It's <span style="font-style: italic">crucial</span> to do that with the small end bushes in the con-rod.
 
I reamed mine to a tight fit too. The bronze bushings will wear in a lot faster than the steel trunnion pins. Too loose in not good and as Randall said, they'll wear out a lot sooner.
 
We just reamed out ours... 19/32-21/32 reamer from enco is what you're after. We drilled ours, and then realized the problem... We purchased new ones, reamed them correctly, the re-installed everything.

You can ream them on the bench. Use a vice to hold the arm, then use a tap holder (from a tap and die set) to gradually increase the size of the hole with the reamer. Do not immediately set the reamer to .625. Start with .615, then .620, then .625. It sorta shaves off little manageable pieces from the inside rather than scraping off big chunks.
 
I hate those cheap adjustable reamers! Got a full set of them, but they are strictly a last resort, IMO.

A fixed 5/8" "chucking" reamer will do the job and still costs under $15 from Enco. The leading edge is tapered, so it also shaves off little pieces.
 
Hmm... I'd never seen the chucking reamer... That would appear to be much easier to use than the one we used.
 
I like the adjustable hand reamers for this application. I think it was Randall that initially recommended it to me. Worked like a dream for hand fitting the bushing to the pin.

It was easy too. :wink:
 
I used the adjustable reamers for this job, and it worked out fine. A bit tedious, but having infinite adjustability is a plus. The set that I'm using was handed down to me from my father. One thing it is not, is cheap. It really is a good set. If you're doing a through hole, they have a long shaft on the opposite end with a sliding tapered centering piece. This keeps everything in alignment. Sometimes I wind up using them at work when I need to ream a hole for a one-off piece...cheaper then going out to buy a chucking reamer in some odd size that will only be used once.
 
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