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Old 07-01-2020, 12:58 PM   #1
philipswanson
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Default Installing Rear Hub On A '40

Do you guys recommend installing the rear hub to the tapered spindle with some light oil or grease on the spindle to ease the fit or installing it totally dry?
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Old 07-01-2020, 01:06 PM   #2
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Default Re: Installing Rear Hub On A '40

Clean & DRY Only! DD
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Old 07-01-2020, 01:08 PM   #3
oldskool
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Default Re: Installing Rear Hub On A '40

needs to be perfectly dry , clean with lacquer thinner or brake cleaner
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Old 07-01-2020, 01:30 PM   #4
philipswanson
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Default Re: Installing Rear Hub On A '40

Thanks, that's what I thought. I just wonder why?? It's not like its going to come off because its secured by a nut and cotter key. So what is the logic of it being dry. Just wondering.
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Old 07-01-2020, 01:46 PM   #5
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Default Re: Installing Rear Hub On A '40

Friction is the answer here. Just like a tapered collett or bit for milling machine or large drill press or even ball joints. The nut is there to keep it together and provide that a force is always keeping it in contact. The keyway adsorbs shock and does transmit part of the load depending on how much "taper friction" is available. Valve grinding paste is good for lapping the hub to the axle shaft to provide a full contact surface. Clean off the grinding compound and clean completely and dry. Assemble and be happy for doing a good job.
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Old 07-01-2020, 01:56 PM   #6
51woodie
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Default Re: Installing Rear Hub On A '40

It has to do with the coefficient of friction. The axle drives the hub through the key, which is exposed to shear force when torque is applied to the axle shaft. The reason for a dry fit, hub to axle, is that the hub is driven up on the taper when the axle nut is tightened, to somewhere around 200 ft/lbs.. The friction is needed to aid in keeping the axle from shearing the key. If the axle/hub was lubed, then friction drops, there is more stress on the key, and a potential for failure. Some people will check the axle/hub fit with machinist blue to confirm there is good contact on the surface area. Don't forget there is a seal (looks like a fiber washer) that fits in the outside end of the hub, before the washer and nut go on.
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Old 07-01-2020, 02:41 PM   #7
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Default Re: Installing Rear Hub On A '40

Makes sense, thanks guys!
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Old 07-01-2020, 02:57 PM   #8
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Default Re: Installing Rear Hub On A '40

Just as a point of info.
If you don't have that little fibre seal,
you can make one out of an old piece of leather....like a belt.
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Old 07-01-2020, 05:05 PM   #9
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Default Re: Installing Rear Hub On A '40

My understanding is that if working properly, the drive is transmitted by friction between the hub and the shaft. In theory, the key isn't transmitting the drive. So imagine you left the key out. What would you do to make the friction drive work? Well, first of all you would make sure the surfaces are as perfect as possible. It is recommended to lap the hub to the shaft. I have done this myself, it isn't difficult. Then you would assemble it clean and dry. Finally you do the nut up very tight.

Obviously you do use the key, but you need to imagine it is not there. So no oil or grease, or lapping compound, nothing but clean metal to metal contact. And tighten that nut until something goes click.

Mart.
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Old 07-01-2020, 05:09 PM   #10
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Default Re: Installing Rear Hub On A '40

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my understanding is that if working properly, the drive is transmitted by friction between the hub and the shaft. In theory, the key isn't transmitting the drive. So imagine you left the key out. What would you do to make the friction drive work? Well, first of all you would make sure the surfaces are as perfect as possible. It is recommended to lap the hub to the shaft. I have done this myself, it isn't difficult. Then you would assemble it clean and dry. Finally you do the nut up very tight.

Obviously you do use the key, but you need to imagine it is not there. So no oil or grease, or lapping compound, nothing but clean metal to metal contact. And tighten that nut until something goes click.

Mart.

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Old 07-01-2020, 08:03 PM   #11
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Default Re: Installing Rear Hub On A '40

It is kinda hard to keep the grease out of the bore in the hub since you have to pass the spindle through the freshly packed wheel bearing area. I like to load the bearings plenty and the end of the axle needs to pass through and will get some grease on it. Tried to keep that to a minimum but some gets in I'm sure.
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Old 07-02-2020, 03:36 AM   #12
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Default Re: Installing Rear Hub On A '40

You need to take extra care. make sure the grease is in the bearing, clear it away from the central part. make sure you get an straight shot at it and if you get some on there, take it off, clean the axle and the bore and do it again.

It can be done.

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Old 07-02-2020, 05:03 AM   #13
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Default Re: Installing Rear Hub On A '40

Question and I don't mean to high jack, but it relates to this discussion.

I used NOS axle shafts and they were perfect, shiny metal. I lapped one side, but didn't install the hub. The follow day, it appears to have a coating of the lapping compound on the stub even though I thought I cleaned it off very well.

Besides chemical cleaners, would it be OK to run a 3M pad or Roloc on the stub to clean it? I don't want to do anything that will mess up the taper.
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Old 07-02-2020, 05:26 AM   #14
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Default Re: Installing Rear Hub On A '40

Clean it off with "lacquer thinner or brake cleaner" (post #3) or acetone.
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Old 07-02-2020, 06:27 AM   #15
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Default Re: Installing Rear Hub On A '40

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Clean it off with "lacquer thinner or brake cleaner" (post #3) or acetone.
I tried brake cleaner and it's not taking off the compound. I'll use a little more elbow grease.
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Old 07-02-2020, 07:32 AM   #16
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Default Re: Installing Rear Hub On A '40

Tim. In my experience, when a shaft is machined properly, the finish is nice and shiny. Some machinists can get a finish that is mirror like. When two parts are lapped together with compound, the finished surface is "ground" away at the high spots by the lapping compound, leaving a dull surface, similar to the surface of 1000 grit wet paper. An example is lapping valves to their respective seats. The seat of a new valve is nice and shiny, but when the valve is lapped, you will see a dull mark the width of the mating surface on the valve seat. Unless you have some real special compound, I think you have it cleaned with what you have done. IMHO.
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Old 07-02-2020, 08:09 AM   #17
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Default Re: Installing Rear Hub On A '40

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Tim. In my experience, when a shaft is machined properly, the finish is nice and shiny. Some machinists can get a finish that is mirror like. When two parts are lapped together with compound, the finished surface is "ground" away at the high spots by the lapping compound, leaving a dull surface, similar to the surface of 1000 grit wet paper. An example is lapping valves to their respective seats. The seat of a new valve is nice and shiny, but when the valve is lapped, you will see a dull mark the width of the mating surface on the valve seat. Unless you have some real special compound, I think you have it cleaned with what you have done. IMHO.

OK, I thought about that and I think/hope you are right. It did seem like there was some lapping compound left over. I'll look it over real good before installing the hub.
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Old 07-02-2020, 11:56 AM   #18
philipswanson
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Default Re: Installing Rear Hub On A '40

The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? With the nut torqued to over 200 pounds, how much slippage could there be with or without a wet or dry axle taper? Have we seen keys break?
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Old 07-02-2020, 12:31 PM   #19
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Default Re: Installing Rear Hub On A '40

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Originally Posted by philipswanson View Post
The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? With the nut torqued to over 200 pounds, how much slippage could there be with or without a wet or dry axle taper? Have we seen keys break?
It is termed a "friction fit". Anything between such as oil or grease or ANYTHING,--reduces the friction and will most certainly break the key and probably ruin the axle.
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Old 07-02-2020, 01:24 PM   #20
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Default Re: Installing Rear Hub On A '40

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Originally Posted by philipswanson View Post
The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? Have we seen keys break?

Is this evidence enough? The hub turned on the axle because not nearly tight enough. Rolled the key right over in the slot...destroyed axle. No myths here! It's exactly the same theory that a Morse Taper works on. That key DOES NOT drive the hub! TIGHT for good reason! DD


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