Polish Axle Tapers?

TBone69

TBone69

Senior Member
Hey Folks,

Using Tom Endy's rear end rebuild article I have started the tear down and cleaning up of parts for rebuilding my banjo rear.

This is sort of a rhetorical question as I have another set of axles in better shape from another rear I parted out. I don't want to junk them if they can be used in the future

Do you think these can be cleaned up?
 

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They actually look very good. No sign I can see in the photos of ever shearing a key and being spun.
 
Consider that the hubs probably look as bad or worse.
If you can lap them and get 90% mating surface they would be reliable.
 
Pete said:
Consider that the hubs probably look as bad or worse.
If you can lap them and get 90% mating surface they would be reliable.
Click to expand...
Pete, I popped a key once & just tightened the nut REALLY TIGHT, and with gentle take offs, I drove 40 miles home!
Bill W.
 
BILL WILLIAMSON said:
Pete, I popped a key once & just tightened the nut REALLY TIGHT, and with gentle take offs, I drove 40 miles home!
Bill W.
Click to expand...

Actually, tests were run many years ago where the hub was lapped to 100% mating surface and installed with NO key. The car was driven for 1000 miles with no evidence of slippage.
 
From the photos the axles look serviceable to me. The threads look very good. I would just wire wheel them or bead blast them. Look carefully for a crack at the key slot after they are removed from the axle housing. The crack usually starts at the inboard end and will eventually work its way around the circumference and then break off. If you detect the slightest crack best to not use the axle.

Tom Endy
 
Hi T-Bone,

FWIW:

With very large vintage drill presses and very large vintage lathes, a key was never used on these tapered connections which were subject to far more axial stress than the far less stress caused by Model A rolling wheel on an axle ..... even when spinning on a hard surfaced highway.

The main difference was that the operators that used these tools were aware of the tremendous value of this friction fit when tightened "properly".

Many former Model A owners and many Model A pseudo-mechanics were fully capable of winning all of the Darwin Awards ever handed out for being totally uninformed.

The guy(s) who tightened your rear axles indicated in your photos were not aware of this tapered friction concept ............... or it was his wife's car that he was hoping that she would fall off of a cliff.

Removing axle "high" spots is the most important task to obtain maximum metal to metal contact ...... leave low spots on axle "as is".

If keyway is good, axle is not cracked, and axle nut is tightened per specs, it will work just great.
 
Thanks Folks. I'll inspect the key ways for cracks but they look to be in good shape otherwise.

A buddy of mine has a large enough lathe we can chuck these up in to spin polish them. Hope to get after Wednesday evening. I'll post up the results.
 
Pete said:
Consider that the hubs probably look as bad or worse.
If you can lap them and get 90% mating surface they would be reliable.
Click to expand...

Actually have hubs and drums from a different rear that look pretty good. I'll still lap them to the axles though,

Tom Endy said:
From the photos the axles look serviceable to me. The threads look very good. I would just wire wheel them or bead blast them. Look carefully for a crack at the key slot after they are removed from the axle housing. The crack usually starts at the inboard end and will eventually work its way around the circumference and then break off. If you detect the slightest crack best to not use the axle.

Tom Endy
Click to expand...

Thanks for the feedback and thanks for creating the rebuild article.
 
The gripping qualities of a taper is MIND BOGGLING!
Is there a FORMULA/EXPLANATION, in laymens' language, that explains it? It "may" be something to do with the INFNITE number of different circumferences, along the length of the taper, "competing" with each other??? The Dog sez I'm a crank NUT!
Bill W.
 
While we are talking tapers check out the taper on my drive shaft. The pinion came right off after removing the nut.

Looks like it had some previous damage from spinning the pinion. This explains the heavy grooves on the carrier. It also had a spun bearing but I have another one in good shape that I will be using.
 

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Make sure you check the drive shaft for cracks also. This one didn't make my day. Especially since it was a shortened drive shaft for a 4 speed. It was shortened at the other end though. Had to have a machine shop cut 4-1/2 inches from the taper end of another standard drive shaft and remachine the taper, keyway and threads.
All better now!
 

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TBone69 said:
While we are talking tapers check out the taper on my drive shaft. The pinion came right off after removing the nut.

Looks like it had some previous damage from spinning the pinion. This explains the heavy grooves on the carrier. It also had a spun bearing but I have another one in good shape that I will be using.
Click to expand...



The carrier bearing on the ring gear side has spun on the hub, otherwise it would not have come off. Both bearings should press on the carrier hubs with an interference press fit. The reason they spin is that the carrier pre-load was not previously set correctly, or not at all. A lot of rear axle assemblies are put together with no thought to pre-load. In a lot of cases the rotation is locked. Henry's 40 horses will break it loose when installed in the car. The result is a spun hub with material machined off the hub and the bearing stop. If not too bad the hub can be repaired by knurling.

Tom Endy
 
bettlesr said:
Make sure you check the drive shaft for cracks also. This one didn't make my day. Especially since it was a shortened drive shaft for a 4 speed. It was shortened at the other end though. Had to have a machine shop cut 4-1/2 inches from the taper end of another standard drive shaft and remachine the taper, keyway and threads.
All better now!
Click to expand...



I suspect the cause of the breakage is the misalignment of the stub shaft to the 4-speed installed. The only time I have ever encountered a broken drive shaft are those that were cut short and used in Borg Warner and Volvo overdrives, and I have seen a bunch. Many of the cottage industries that built them did not have accurate alignment jigs. Any off-set puts a load right at the front end of the key, and that is where they break.

The builders of Volvo overdrives in Bakersfield, CA (Rich and Mitch) understand about alignment and their units are jigged and in proper alignment. An old fellow, Bert Hiller, who I think has since passed away, knew the definition of alignment and his Borg Warner units were well built and in alignment.

Tom Endy
 
Back to what Pete said. An SAE 9 to 1 taper is considered to be a self locking taper, if properly fitted to the mating part. The keyway is only a fail safe to get you home till you can fix it. Rich
 
Tom Endy
When I looked back at the rear the broken driveshaft came from I found it had a couple of broken teeth on the ring and pinion. I think the previous owner sorta abused it a bit.
Dick
 
TBone69 said:
. . .A buddy of mine has a large enough lathe we can chuck these up in to spin polish them. Hope to get after Wednesday evening. I'll post up the results.
Click to expand...

I would suggest you use a new, flat India or sharpening stone and oil, not emery cloth to dress the tapers. You want to knock down any high spots, not just polish over them. Inspect the internal taper on the hubs for high spots, too. They can be dressed out by hand.
 
The ends look good to me, but before you start turning them down or otherwise removing material, make sure the hubs fit so that the end of the hub is a couple of threads out. Minimum should be the end of the hub is at the end of the threads so the big washer gives you room to tighten them down. If the hub is too far in, you will not get them tight, and the drums may even rub on the brake shoes or backing plate.
 
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