Is A .861 Reamer Too Large For A .859 Kingpin?

Is a .861 reamer too large for a .859 kingpin? Would there be too much slop in the bushings?

 

.002 would not be excessive.

 

I haven't replaced kingpins in 25 years (on a '53 F-100) so I did a quick internet search. This site says reamer can be .001-.003" larger than bushing.

http://econolines.ipbhost.com/index.php?showtopic=1963

 

Well I paid for a .859 reamer that got lost in the mail. I've got a chance to get a .861 reamer for way less than the cost of a second .859 reamer.

You should have seen how that reamer got lost in the mail. I received a flat rate USPS, empty box with a small, .859 hole in the side of it. The only thing that was left in the box besides the packaging was the plastic bag that held the reamer which coincidentally had the same .859 hole in the side of it. A real Duesy...

 

I respectively disagree.

As a retired machinist and having installed king pins on more cars than I'd like to remember, I don't think it's a good idea. .002"-.003" is a lot of looseness and would cause too much looseness with the king pin which would only get worse with wear.

The proper fit for a king pin, on most designs, is a finger push with no looseness. Do it right the first time.

 

As a former Aircraft machinist I wonder just how much clearance you recommend on something like this other than "a finger push with no looseness"? I am not being facetious, I have worked with clearances all the way down to 7 decimal places with the usual being in the .0005 +/- .0002 range. A sliding fit can be construed as .0005 by one person and .005 by another with that additional zero making a huge difference. I am just curious.

 

.002-.003 is too much. This quote is from a Wikipedia page on fits. I use an adjustable reamer which allows for any fit you want. Reaming a bore to .861 using a .861 reamer will be difficult at best for a non-professional, which I assume the OP is.


"The tightness of fit is controlled by amount of interference; the "allowance". Formulas exist to compute this allowance (planned difference from nominal size) that will result in various strengths of fit such as loose fit, light interference fit, and interference fit. The value of the allowance depends on which material is being used, how big the parts are, and what degree of tightness is desired. Such values have already been worked out in the past for many standard applications, and they are available to engineers in the form of tables, obviating the need for re-derivation. Thus if a loose fit is desired for a 10 mm (0.394 in) shaft made of 303 stainless steel, the engineer can look up the needed allowance in a reference book or computer program, rather than using a formula to calculate it. For non-commercial parts, there are 'rules of thumb' for Steel and Aluminum. For tight fits the bore diametrical tolerances for a press fit with a rod constraint are given by subtracting .0001-.0003 inches (1-3 tenths; slang for ten-thousandths). The rod tolerance, with a bore size constraint, can be found by adding 1-3 tenths to the given bore diameter. For slip fits the bore diameter must be .0005-.0008 inches wider than the rod. Transversely, the rod must be .0005-.0008 in. under the given bore diameter. These broad guidelines save the trouble of having to calculate or look up tolerances for a single instance piece."

 

while the extra .002 may not give you any trouble , i have to agree with TagMan... get the correct size reamer. do it right the first time and make it last. why have .002 of "wear" built in?

 

I plan on haveing my local engine rebuilder hone the installed bushing honed to fit the kingpin. I was quoted $25-30. I have had spindles reamed and I prefer the honing. OMO

 

I feel the need to repeat myself. I bought the right size, but the damn thing punched its way out of the box it was shipped in. I don't enjoy throwing $100 dollars away on empty USPS flat rate boxes.

 

Remember that it will probably cut slightly larger than .861 as well.

 

I expect it to cut larger even with a genuine .859 reamer. Speedway is starting to sell the .859 reamer now, and they list in the description that it cuts the bushing to .860.

 

If the .859 reamer will give you the right clearance as you said, then the .861 will be .002 too big. A tighter fit of .001 or less clearance is commonly accepted as the correct fit for kingpins. Try MSC or McMaster-Carr for a reamer, they might have a cheaper alternative in the right reamer for you.