Reaming with an adjustable reamer

I have had occasion to do this for some bushings and had similar problems. I found that what worked was to insert the reamer through the bushing set just slightly snug then expand a bit, twist, expand a bit, twist, ... If you get too aggressive with those, things go to Hell in a hurry.

Ted

My personal experience with adjustable reamers leaves a whole lot to be desired. If I had at my disposal either a lathe or mill, and could bore the bushings, I wouldn't even consider using a hand reamer, adjustable or not. The best reamed hole won't come close to the quality of one that has been bored. Hand reamers will cut in any direction you point them, and are notorious for yielding holes that are out of round and tapered. You have a lot better chance of holding the size you desire by boring.

Harold

Harold, I agree with you wholeheartedly, but with the odd shape of a MG rocker arm, I have found no way to mount it in my lathe and no easy way to cente and recenter it in my mill for a multistep operation. I use a adjustable reamer in my lathe often to make distributer bushings without any problems because everything is held firm and true. There has to be a method to do this easily or they would never get rebushed at the motor rebuild shops.

That certainly changes the complexion of the issue. I have to agree, often times holding an item can be most frustrating. Still, there may be certain features that were used originally when the item was produced which could be reliable used again in holding them for a rework. I'm not suggesting I know of them, just that they exist. You may be able to detect a particular trend by examining a few of them, then try a simple holding fixture. Unless you are working against the clock, this could be a fun challenge to solve. Why don't you let us know what you learn in the end? Anyone that faces the same problem could certainly benefit by your efforts.

Good luck with the project~

Harold

"GM, You mentioned that you have a lathe. would it be possable to make bushings for the reamer. The first bushing could be off the head mounted to surface that head is mounted to, holding one end of reamer. Second bushing in second rocker arm bore. Move down the head one bore at a time bushing on each side of reamer.

George,

Remember the early bird gets the worm BUT it's the second mouse that gets the cheese.

------------- The name of the game is Sunnen hone! take the rocker arms to your local auto machine shop and have them honed professionally. Don Warner

|"GM, |You mentioned that you have a lathe. would it be possable to make |bushings for the reamer. The first bushing could be off the head |mounted to surface that head is mounted to, holding one end of reamer. |Second bushing in second rocker arm bore. Move down the head one bore |at a time bushing on each side of reamer.

I understood the bushings to be reamed are in the rocker arms themselves, not the shaft mounting points in the head. Since rocker arms are typically machined only in bore and extremities, workholding would be a real challenge on any design I'm familiar with. Rex in Fort Worth

I just happen to have a Sunnen Hone for sale, very cheap

Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

My problem is with the rockers, themselves. They are too irregular to grasp in any chuck that I know of. I can clamp them in a vice but really have no good way to do the reaming and being sure that the bore is truely vertical. Looks like I'll just have to farm this job out to an automotive machinf shop. Thanks for all the suggestions!

Do the rockers have adjustable tappets on them? If so, this gives you the reference that you need. Use a right angle plate with a bolt through it into the tappet hole to eliminate one degree of freedom and use jacks and clamps to eliminate movement at right angles to the bolt. Use a rocker that has not already been reamed if possible (assuming they are identical, may be two or more patterns in the head). Once you have the basic setup on the drill table or lathe faceplate ream them, preferably with a machine reamer, but if not, then with a hand reamer in a chuck. The ones that you have used the adjustable reamer on will have been slightly buggered due to the chattering but the worn ones will probably still give a good enough reference for setting up...I didn't say it, but use a bit of bar through the rocker spindle hole to verify that it is aligned with the lathe/drill axis.

This process, or similar, should work.. I have used it with Mini suspension radius arms and with Triumph motorcycle rockers.

Mark Rand RTFM

I made the rocker arm bushings for my 3 cylinder Fiat diesel by turning the bushing stock to diameter in the lathe, then pressing bushing into rocker arm with excess stock attached. Rechucked stock/rocker arm in lathe, then bored ID to size. After that, I sawed off the arm from the stock. The rocker arms were rechucked on an a homemade internal expanding arbor to face the sawed end of the bushing. It all went very well.

RJ

Cute idea. That way you wind up with a very round, straight bore, and you can control the diameter accurately.

The ream typically specified for pressed-in bushings is get over the taper or bell-mouth that usually occurs during a press fit.

What was the bushing material for those rockers, in that engine?

Jim

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Jim, the original bushings seemed to be brass, not an oilite type material, so I used some brass thick wall tube type material we had at work that we use in production. I'm not sure of the alloy, but I could look at the prints. I figured that since they are oil supplied, it wouldn't present a problem. They have been in service for 13 years now. The rocker shaft showed some slight wear marking, so I flipped it over to present the pressured side of the bushings with fresh shaft area to ride on. When I first got the tractor, the starter was trash, so I took the starter bendix apart, mated half of it with half of a Chevy starter bendix to retain the original drive gear, and by making one simple bushing, adapted the tractor with an easily obtainable starter. I just recently found out that Bosch makes a replacement starter for this tractor, for $160, but this one works fine, so what the hey. My investment so far in this 35 hp tractor is just $750 and I've used it for all this time.

RJ