Axles, just a thought

[daveymc29]

I sheared a shear-pin on an axle on my couple. I had a look at the pin and axle on the other side also. Both hubs appear to be pretty good shape, a couple of minor groves in each, but the axles both show evidence of having had the hubs shear a pin and then turned for quite a few revolutions, cutting several minor groves and each has one well pronounced grove. The axles run spot on with the new key and 125# torque. I'm thinking that to improve the contact area I could very carefully clean the groves and JB Weld them back up, file them to as near to original as possible and re-install the wheel and hubs. What would it hurt? It apparently has worked pretty well scored, so with the scoring removed, won't it work even better, maybe help prevent a repeat of shearing the key? Your thoughts?
Thanks as always, Dave another new guy.

[hardtimes]

Hey Dave,
The axle key is NOT the what should be keeping properly fitted hub and axle in proper relation to each other. Proper lapping and tightness of these two together WITH proper torque is what to strive for. Of course with worn out parts, shims with proper /adequate torque will also suffice. Do not put yourself in the position of depending on the key to hold these critical parts together.

[Joe K]

Hmm. I know what you're trying to accomplish (get to a "tighter" fit between taper and hub)

Make a logical extension to the thought - what if the "recess" were at the largest part of the taper? And you relied upon the outer 2/3rds of the taper to keep the hub on the axle? You've reduced the axle section in bending and proportionally reduced the strength of the axle as cantilever at the inner hub.

Or put the recess at the smallest 1/3rd of the taper. Now you've reduced the diameter and strength (and resultant compression to the taper) of the threaded portion of the axle holding the hub to the taper, just as if you turned down the threaded portion from 5/8" diameter to 9/16"

To reduce a section in the middle of the taper reduces BOTH of these to some smaller proportion.

Now the argument could be made that the scoring has ALREADY done this.

I say give it a try. You'll increase the unit pressure per square inch between the taper and the hub for the 2/3rds of the taper that remains and touches. And pressure on the taper translates through coefficient of friction to resistance of turning the hub on the axle.

Again I say - if you can achieve full torque on the nut - you're probably good to go.

and "transition" that recess at either end so as not to form a stress concentrating raiser at the juncture between recess and taper.

Interesting mind exercise - both in the consideration and in putting it to words.

Joe K

[BRENT in 10-uh-C]

Hard times is pretty much spot-on with his thoughts above. Contrary to what many do, there are many hubs that are worn out and need to be replaced due to wear inside the taper or grooves on the axle which if severe enough can set up stress risers.

[1930artdeco]

As long as we are on this topic. What is the best way to tell if the hub/axle mating surface is 100% correct and tight?

Mike

[BRENT in 10-uh-C]

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Originally Posted by 1930artdeco

As long as we are on this topic. What is the best way to tell if the hub/axle mating surface is 100% correct and tight?

Mike

Best way is to look with a bore scope. Even Harbor Freight sells tiny cameras to peer inside of such areas. Next way is to use Prussian Blue to check contact area.

[Mitch//pa]

Originally Posted by 1930artdeco

As long as we are on this topic. What is the best way to tell if the hub/axle mating surface is 100% correct and tight?

Mike

if one or both of the tapers are worn the drum would rub the backing plate or shoes.. the axle shims are for worn tapers but they can only make up for so much excessive clearance......

[Joe K]

I like the prussian blue. Even better using black magic marker.

I've made tapered centers for the lathe and used magic marker to blacken the center and check fit. For a lathe if you get 80 percent contact, that is considered good enough. (it will change when you use the lever to clamp the tailstock quill.)

Joe K

[hardtimes]

I agree with Prussian blue use/statements. Being of meager tools/skills (), I love the 'black magic marker' use idea and use it for many things. Hm, just wish that they weren't so darn expensive ,eh !

Now, to the 'both' worn statements and use of shims. Recently, I put NEW drums on my worn axles. Yup, had to use two shims and a little black marker to grind off the parts rubbing (backer to drum) surfaces. Quiet as a mouse now and got 175 lbs of torque on each axle nut comfortably !

[Mitch//pa]

i have used the prussian blue also

[RandyinUtah]

Correct me if my thinking is off on this worn axle subject. My thinking is if you have a loose fit between the axle and old original hub the problem is because the hub has expanded over the years. My thinking is the axle would not shrink to a smaller size over time due to compression. If one purchased new hubs the axle /hub taper would again be a tight fit and no need for axle shims. I previously had to use axle shims but they were not needed after I installed new hubs. I think my old original hubs had expanded over time. Please comment on my thought process.
Thanks Randy

[Joe K]

I think my old original hubs had expanded over time. Please comment on my thought process.

"Stretch" is the operative word. I think bolting the hubs on and pushing them up onto the taper stretches the hub centers and makes the hubs/drums end up too close to the backing plate.

New hubs, mean while, are made to the original Ford drawings - and should reflect what the car was when it was new.

Joe K

[Tom Wesenberg]

Here's what can happen if you don't have a tight axle nut. The key takes all the driving force rather than the axle taper tight fit to the hub. This axle is mint except for the wide keyway.

[1929]

My whole front end is in the shop at Antique Ford in Bohemia being repaired from very poor maintenance from the previous owner, he couldn't understand why his steering was very hard. The axle and radius rod, drag link, tie rod, perches, front spring, most front end has to be replaced, there was loose nuts and bolts and some wrong size bolts. After seeing all this on this car I can only believe that there has to maybe be about 75% cars out there that need work on the front ends due to improper maintenance and the age of these vehicles.

[dave in australia]

One other cause for the taper not gripping and relying on the key is some form of lubrication between the axle taper and the hub. I heard some old timers say to use a bit of grease on the axle before installing the hub. This doesn't allow the axle and hub to grip each other through friction, which is what a taper relies on. When I bought my tudor, this was one of my rear end tasks, as well as a lot of work on the brakes just to get them up to a safe standard. Never assume the prvious owner knew anything about A's when they worked on them, let alone knew anything about mechanics in general.

[Joe K]

The question of lubricating machine tapers has been discussed in the machine taper world. See http://www.practicalmachinist.com/vb...tapers-233868/ for a three post entry regarding why or why not to lubricate morse or other machine tapers.

Quick overview: tapers are generally lubricated lightly on even self locking machine tapers primarily to allow disengagement without galling after the work is done.

I'm not so sure I would be that generous. Maybe a small amount of WD40 or other light lubricant? Maybe for no other reason than to exclude water and prevent rust?

Although rust would "fix" the bond, wouldn't it? And make the taper even less likely to come apart? But that would make new brake pads more difficult too, of course.

Joe K

[Mitch//pa]

Originally Posted by Joe K

The question of lubricating machine tapers has been discussed in the machine taper world. See http://www.practicalmachinist.com/vb...tapers-233868/ for a three post entry regarding why or why not to lubricate morse or other machine tapers.

Quick overview: tapers are generally lubricated lightly on even self locking machine tapers primarily to allow disengagement without galling after the work is done.

I'm not so sure I would be that generous. Maybe a small amount of WD40 or other light lubricant? Maybe for no other reason than to exclude water and prevent rust?

Although rust would "fix" the bond, wouldn't it? And make the taper even less likely to come apart? But that would make new brake pads more difficult too, of course.

Joe K

brake shoes

[Chris in CT]

[QUOTE=Joe K;1040312]The question of lubricating machine tapers has been discussed in the machine taper world. See http://www.practicalmachinist.com/vb...tapers-233868/ for a three post entry regarding why or why not to lubricate morse or other machine tapers.

Quick overview: tapers are generally lubricated lightly on even self locking machine tapers primarily to allow disengagement without galling after the work is done.

I'm not so sure I would be that generous. Maybe a small amount of WD40 or other light lubricant? Maybe for no other reason than to exclude water and prevent rust? [Quote]

Hi Joe, I note that the link you posted above contains the opinions of guys like ourselves who are basically hobbyists, and not experts on taper design and application. Permit me to give a loyal and friendly opposing view to the proposition that tapers should be lubricated:

Tapers are designed to be "work holding" apparatus, used to extend or connect shafts in such a way as to maintain full strength of the assembly without introducing any free play, lash, or lost motion into the extended assembly. They need to be clean and dry, and free of rust or any surface contamination in order to function as they were designed. Many are held in their fixed positions by drawbars (or push-nuts in the case of the Model A).
Certain Morse Tapers are only connected by the force of pressing the male taper into the female taper receptacle, relying on a "tang" or rectangular tab at the end of the taper as insurance against rotation if the tool should "hog" into the workpiece, or vibrate loose.

Any form of lubrication will only work to break the integrity of the bond between the male and female parts of the joined taper assembly.

What causes galling is the rotation of the male taper inside of the female portion. Tapers are designed to be separated by direct linear force pulling the male away from the female taper, frequently assisted by a sharp rap to the male end of the taper (or to a loosened drawbar, or to an ejection pin).
There will be no galling to a properly removed taper if it is clean and contamination free.

And...no jokes about male and female tapers, please!

Chris

[Joe K]

Originally Posted by Chris in CT

And...no jokes about male and female tapers, please!
Chris

Funny. You google "lubricate tapers" and you get several web pages on "earcandling."

We mess with machines, they do strange hot things to their ear canals?

As I said, I wouldn't necessarily buy into the Practical Machinist Forum argument and your overview a cogent look.

Confirmed by https://books.google.com/books?id=F9...0taper&f=false which states "don't oil the taper shank of the centers, spindle-adaptor sleeves, and drill-chuck shanks, as a film of oil prevents them from seating properly."

Notice the wording. "A film of oil." I still like the thought of a quick wipe and wipe off with a light oil - if for no other reason than to remove perspiration and the oil from one's skin that one might otherwise leave on the taper.

And in defense of a little lube, there might be something to establishing that "stretch" of the hub radially we discussed earlier, a necessary part of "putting on" a hub. One can't establish a pressure psi without stretching the hub below it's yield point, or possibly above. One imagines that without ANY lubrication that pressure would be highest just under the nut, and in decreasing levels of psi as one approaches the axle full diameter.

This phenomenon reason that a post-driving recommendation is made to "touch up" the hub nut torque. One imagines that the rolling action tends to "even out" pressure across the taper and in doing so, relieves some of the tension under the nut. Tension that is restored in the re-torque.

And a lubricant may help this "evening out" to occur faster? And more positively to it's final tension/pressure?

MANY ways to look at this.

One has to be careful in use of the Internet as a reference source. Just about ANYTHING has been said given enough time and discussion.

Sort of like the mind-exercise considering monkeys randomly typing at a keyboard: eventually, given enough time, they will type ALL known documents?

Including the incorrect ones?

Joe K

[hardtimes]

Originally Posted by dave in australia

One other cause for the taper not gripping and relying on the key is some form of lubrication between the axle taper and the hub. I heard some old timers say to use a bit of grease on the axle before installing the hub. This doesn't allow the axle and hub to grip each other through friction, which is what a taper relies on. When I bought my tudor, this was one of my rear end tasks, as well as a lot of work on the brakes just to get them up to a safe standard. Never assume the prvious owner knew anything about A's when they worked on them, let alone knew anything about mechanics in general.

Hey Dave,
X2 ! The idea of lapping is to get 'perfect' matching surfaces between these two. Any lube on either surface would defeat this purpose, IMO.