Front Axle Repairs

Glenn C.

Glenn C.

Well-known member
What is the best method of repairing the worn king pin bores of the front axles ? Is there a procedure available for a proven method ? A few members of our club have expressed a desire to have their axles checked for straightness, along with resizing and re-calibration of spring perch bore to spindle bore of the axle.
We do have a NOS front axle available for comparison of measurements.

Your help and comments are always appreciated.
 
Hi Glenn,

Several Model A Front Axle Forum Articles with photographs and specifications were written and can be found under "Search"; and/or in Model A magazines.

In my opinion, the next step would be to present these detailed measurements and specifications to a reputable, experienced qualified machinist to inquire if he is interested in providing this work.

The "different" required machinist correction work for each individual axle will be about as "different" as sending 20 senior Model A owners to a dentist .... each with different bent, worn, and missing teeth ...... plus some with false teeth.
 
Thanks HL
Your response is appreciated very much. I read through the postings under the "search" tool, and found nothing in reference to our particular repair situation. There was several comments regarding spindles, and a few others referring to other matters, but nothing regarding procedures for restoring the "King Pin" fit to the axle. I have all of the "Restorer Books" except for Volume 9. So I will now check those and some other reference books that I have.
 
Hi Glenn,

In your reply, " but nothing regarding procedures for restoring the "King Pin" fit to the axle."

Once the king pin bore in a Model A Front Axle is badly worn such that the king pin is excessively loose, the worn bore will not resemble a perfectly oversized cylinder that can be fitted with a perfectly uniform diameter oversized king pin.

The uneven front axle king pin bore will have to be accurately re-bored out, accurately fitted with a new steel sleeve, and lastly install a brand new king pin.

For comparative thinking, this mechanical machinist procedure is really not that much different in theory from having a well worn Model A engine cylinder, where the unevenly worn cylinder is very accurately re-bored and accurately fitted with a new engine cylinder sleeve ....... followed by installing a brand new piston.

Hope this helps.
 
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I have heard of heating/quenching to shrink the hole, but others say it's not a good idea. I jerry rigged mine to get me thru driving season, then replaced the axle with a good one. Take a perch and king pin with you when searching, to check bores. If they're bent, that's easily straightened. Not sure regarding a twist. I put mine in a vise and leveled with a piece of heavy angle iron, then Use a magnetic angle degree tool available at hardware stores to check king pin angles.
 
The axle on my car was belled out from wear so I had a machine shop drill the axle oversize until round and then they made a sleeve and pressed it into the axle. Then using the new Kingpin they drilled the sleeve to size. If I was to do it again I would find a good original replacement axle.

John Poole
 
forever4 said:
How exactly does a king pin bore get "worn" or "excessively loose"?

There are no direct wear surfaces on an axle except the top of the ends where the thrust bearing rides, and on the beam where worn out shackles sometimes scrub.

Bent and twisted yes, but I have never understood how the king pin bore wears according to threads like these.

The wear is in the bushings of the spindle. The pin is a tight slip fit and is locked to the axle and does not rotate or translate. At least that is my experience with about a dozen Model A/B front ends I have torn down and/or built.
Click to expand...

Vince,

Not sure what caused it, but I have an axle with the ends all wallowed out. Surprised me too, but I can not deny the fact they are messed up.
Naturally it is one of the nicer looking ones that was not heated to get the perches out. I had it all cleaned up and was just test fitting stuff and could not believe they were moving so much. Good thing I caught it before I got further along. In the end, 4 axles and only one that I would use. The other 2 were real soft at the perches from heat so they were not what I would use.
 
Kevin in NJ said:
Axles are cheap and plentiful. Ask around for a good one.

You want one that has a snug fit and not been heated to get the spring perches off.

Front Axle Straightening
Click to expand...

We always seem to get these type of responses. As though there are 80 year old axles hanging off trees.

I have been at many auto flea markets in North Jersey and have seen very few axles , and the few that were found were in poor shape.

I would take that worn axle to a truck suspension repair shop and have them bore and re-bush it to new specs.
 
I am of the belief that the kingpin bores get egged out because owners are not keeping the lock pins tight.....they need to be checked every so often.....everything on an A vibrates loose........
 
forever4 said:
How exactly does a king pin bore get "worn" or "excessively loose"?

There are no direct wear surfaces on an axle except the top of the ends where the thrust bearing rides, and on the beam where worn out shackles sometimes scrub.

Bent and twisted yes, but I have never understood how the king pin bore wears according to threads like these.

The wear is in the bushings of the spindle. The pin is a tight slip fit and is locked to the axle and does not rotate or translate. At least that is my experience with about a dozen Model A/B front ends I have torn down and/or built.
Click to expand...

I happens when some one does not tighten the lock bolt tight. The king pin starts to turn and move with every little bump or turn of the steering wheel. It takes time, but it does happen. I have seen it many times when I was working on cars and trucks for a living.

But once again like a lot of problems on here, some one did not do the job right.
 
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I want to thank each of you very much, especially Kevin & Chuck for their earlier postings. I am personally opposed to boring of the axle ends to renew the fit of the king pin, due to the fact a person would be removing parent material. Shrinking of the axle bores "might" be the preferred alternative, but then again, you still have to ream the bores to the king pin fit, which again is removing parent material.

I was going to machine a forming die that match the forged end of the axle, and would be used in a 30 ton press after the axle end had been heated with a torch. But again, not being a metallurgist, this procedure could be chancy at best, not knowing what temperature the material should be taken to. The axle would have to be cooled very slowly in a pail of Zeolite to maintain the molecular structure and strength of the material.

Heating with a torch will do one good thing for sure, and that is to show if there are any cracks present. I believe these distorted axle ends are "stretched" oblong and are not worn by loose pins. You have a huge force being applied top to bottom on the axle end, when you take in the leverage to the outside of the tire diameter.
 
Unless you have experience in bending metal, I'd excuses yourself and find someone how does... Some metals heat can in fact make it weaker and should not be used. Get an expert..
 
forever4 said:
How exactly does a king pin bore get "worn" or "excessively loose"?

There are no direct wear surfaces on an axle except the top of the ends where the thrust bearing rides, and on the beam where worn out shackles sometimes scrub.

Bent and twisted yes, but I have never understood how the king pin bore wears according to threads like these.

The wear is in the bushings of the spindle. The pin is a tight slip fit and is locked to the axle and does not rotate or translate. At least that is my experience with about a dozen Model A/B front ends I have torn down and/or built.
Click to expand...


True, Vince, if the unit has been greased regularly through the years. I did have a problem with a later model Ford where the car had not been greased in years and the wedge pin was missing, probably since a prior backyard bushing replacement. The bushings had frozen up and the king pin was rotating in the axle bore instead. That bore was really messed up.
 
It maybe the right side that ovals out mostly from hitting the curbs, the early king pin lock bolt (round type) only locates the king pin and does not hold it secure, early 29 the wedge lock bolts were used.
 
It is a shame now, a lot of good shops that were in business had those kind of experts, but for some reason, age has stepped in and they are dying off.
 
A few years ago, I selected 6 straight axles from my collection and proceded to repair the king pin bores, as well as 1 that had a worn spring perch bore. I bored the damaged bores out, to a size that retained enough steel in the axle not to weaken it, but to also allow enough thickness in the sleeve so it also wouldn't squeeze out. I turned up the sleeves from a few old unrepairable rear axles that I had. I then pressed the sleeves in to the axle, and then did a final hone to size to suit new kingpins, and 1 spring perch. I would not heat the axle and quench the ends, as this can alter the hardness and temper of the axle, and make it weaker, and maybe even brittle in the kingpin bore area. If this cracks or breaks, then there's not a lot holding the kingpin and spindle on your car.
 
I believe some axle bore become enlarged when an individual with an acetylene torch and a big hammer heats up the axle and proceeds to pound out the king pin when they are stuck or rusted. He mushrooms the king pin and then continues his hammering till he enlarges the bore of the axle. I have bushed several in a mill and pressed in bushings with a .060 wall and re-drilled lock pin hole.
 
I have no problem with taking the twist or bend from a front axle cold, but after reading the posts of all you guys, I have become gun shy with the thought of using heat to reform the axle ends without extreme knowledge and experience with metallurgy. It may be alright to experiment on one, but it would have to be tested in a lab. Would A Brinell Hardness test be adequate, where a comparison along the axle be used as a datum ?
 
Heat and the axle....

My thoughts.

My experience when figuring out the axle straightening was simple. The axles that were never heated took like 18 hard pumps to make like 1/8" of movement from the perch to the end (they bend at the perch mostly). An axle that is heated for perch removal the 18 pumps feel like you are moving butter and cause over 1/2" of movement.

So if ordinary bumps and bangs of driving and parking can move the axle that is hard, how fast will minor stuff cause the axle to go out when it is heated?

If you drive a little and not fast you are probably fine. If you like to drive the car as can be driven then you probably need to seek out better. My opinion is the guys with heated axles (this includes the dropped ones) are unlikely to ever check the axle after it is installed. So we really do not know how well an axle that was heated stay straight in service. Bear in mind any reports on straightness need to be qualified on use of the car.
I want to not worry so I will spend the time and money to get a better axle.

Be informed, make informed choices with the best facts you can find.
 
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