The Stovebolt Site Forums The Shop Area Engine Shop Reaming the King Pin Bushing

In my manual I read, that the busing for the king pins have to be reamed after installation. Does anybody know the exact diameter for the reamer? The problem is, that I only have metric tools. So what can I do?

The manual shows the use of an adjustable reamer... perhaps one of those would work... if they still make them.

ApachePride,

The reamer size will be dependent on what size king pins you end up with. Depending on the condition of the axle eye, you might have standard pins, .010 over pins or maybe larger...if they make them.

Each size would require a different reamer. Reamers are not cheap to buy. This is why it behooves one to take the spindles to a automotive machine shop to have bushings installed and honed to a perfect fit for the pin.

A '59 Apache should not need the bushings reamed. I think it is only 1 ton and above that need this service. A set for your truck should have bushings that are already the exact size for the pin.

Nothing should be cast in stone until you get the pins out of the axle and see what the condition and fit of the axle eye is. This is the starting point for your rebuild. Have you read the Tech-Tip on king pins yet?

Stuart

Hy Guys, the only thing I would add to this discussion, is both bushings must be reamed simultaneously, otherwise they end up not in line, hope that helps.

Ditto, A very important point 3B

i just had this talk with my boss. he has been in the big truck repair world for years. he said that he has fit the bushing in the spindle and then used a small wheel cylnder hone to hone the bushings to fit the king pin.

It's best to fit those bushings with a Sunnen power hone, or something similar. The other option is a piloted reamer, where the holes end up in alignment. Using a brake cylinder hone, or other methods of cutting the bushings one at a time will result in excessive looseness, and a very short-life repair. The hone I used to run at an automotive machine shop had special long mandrels for kingpin honing so the holes would stay in perfect alignment. It really wasn't that expensive of an operation.
Jerry

it would take a special reamer that would cost way too much
the guy who said take it in to be sunnen honed is on the money
philip

I just noticed you're in Germany. I'd suggest taking your spindles with the new bushings installed, and your new king pins to an automotive machine shop and giving them a clearance specification of .0025 MM. That's the equivalent of a 1/1000 inch slip fit. That would be about the clearance obtained with an adjustable reamer. If power honing equipment is available, it would be possible to get a .001MM clearance, or closer, but it's necessary to leave a little room for lubrication. Chassis grease has a hard time squeezing into gaps of less than .002MM or so.
Jerry

What size truck are we talking about??

A 1/2 ton doesn't need to be reemed. The king pin bushings are finished sized to fit.

It is a 1/2 ton.
The 1/1000 inch slip fit helps, I can measure the king pin and the bushing and see if a reaming is necessary!
Thanx to all!

You won't get an accurate measurement on the bushing until after it is installed in the spindle.
Uninstalled chances are it is not completely round and you can't account for how much it shrinks/compresses when installed. It could be loose now, and to tight when installed, which would then require reaming/honing.

You can however get a guess at it, if it slips over the king pin now then likely it does not need to be reamed after instillation, but this is just a guess, the real answer comes after you install the bushings and test fit the pin.

Grigg

Grigg, unless a bushing is built pretty sloppy before installation, it will tighten up sufficiently to need reaming after it's pressed into the spindle. The inside diameter shrinks as the OD is compressed to go into the housing. Some bushings are made oversize deliberately to allow for that shrinkage, but a slightly out-of-round hole will sometimes create a tight spot. Piston pin bushings do the same thing quite often. They're a slip fit over the pin before they're pressed into a rod, but need honing after they're installed.
Jerry