Hub Hardness and Cutting
 

A friend of mine is helping me redo my brakes and we were having a hard time cutting one of the hubs on the lathe even with a carbide bit. He remarked that "some hubs cut nice, others are very difficult."

This led me to think: why is that? Ford obviously hardened the hubs originally but why are some harder than others?

Re: Hub Hardness and Cutting
 

Do you mean "cutting the drums"? I see no reason to cut the hubs. sometimes cast iron drums can get quite hard if they are overheated.

Re: Hub Hardness and Cutting
 

chrs, if you are talking about original steel drums, they are very difficult to machine. They squeal and chatter terribly.
If you're talking about the rear hubs for a wheel bearing repair, they are hard at the diff end and as soft as cheese at the outer end. Ford's hardening process here left a bit to be desired. That said, they did last for a surprisingly long time. If they were hardened properly, we would never need to repair them even after all this time and who knows how many miles. From Ford's perspective in the day, that would have been overkill.

Re: Hub Hardness and Cutting
 

I am talking about truing the hubs on a lathe. You take off metal until it is hitting everywhere.

Re: Hub Hardness and Cutting
 

Ummmm, you don't need to take it that far. Just a skim pass of no more than 0.005-0.010 is sufficient. This generally trues the area around the hub bolts which is all that is needed. The issue with taking too much off of the hub is it locates the drum closer to the Brake Housing (Backing) Plate and it also affects the riveting process of the bolt due to the bolt shoulder being too long.


BTW, an interesting bit of 'trivia' that I learned awhile back. We have all used the term swage when we discuss installing new brake drums. Actually, when you study the A-1107 and A-1118 Ford print, it refers to the term 'Rivet' when it states to "Rivet over after assembly" on the print (see below). So when you look for the definition of 'swage', it is actually the special tool that is used to rivet the hub bolts -and not the procedure itself. Funny thing though, you 'rivet over' the rivet. :D

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Re: Hub Hardness and Cutting
 

Definition of swage:
https://www.merriam-webster.com/dictionary/swage

Re: Hub Hardness and Cutting
 

I got my definition from a machinist handbook. I wonder where Webster got their definition?? :D :D

Also, I wonder why Ford Engineers used the term Rivet instead of Swage??

Re: Hub Hardness and Cutting
 

Some online instruction advise to "clean up the hub mating surface" on a lathe to give a square/perpendicular/level mount for the new drums to go on. THEN at the end the drums are "trued" in usual fashion.

I can see the desire - but as Brent says "How close does it have to be? One imagines it is possible to "true" the hub far closer than any wheel or tire (especially) applied to it.

Some perspective here...

Joe in NH

Re: Hub Hardness and Cutting
 

So you face the rear hub true and then bolt it on an axle that is 80+ years away from being true with the taper running concentric to the centerline. You may end up better or WORSE than where you started.

If you are into overkill you might as well pull the rear axles and true the tapers. Then deal with all the problems of using those dreaded spacing shims on the axle.

If you want to talk overkill without pulling the rear axles, prudence would have you crazy with dial indicators figuring out what combination will make things perfect with that particular hub mated and indexed by the key-way on that particular axle. You could end up facing those hubs on an indexed plane NOT exactly 90 degrees to the axle center-line. Lunacy! But the drums would then run true... :rolleyes:

Re: Hub Hardness and Cutting
 

Mike, to a certain extent I do agree with you however I am of the opinion that the foundation for drums/hubs running true to the centerline is set by the axle housing race, the hub bearing, and the ID bore of the rear hub where the bearing rides. If everything is within specifications, the axle shafts will be in a perfect centerline.

As far as axle shims, when I am rebuilding the axle housings, I generally remove about 0.030" from the mounting face where the brake housing (backing) plate attaches. This mounts the brake housing plates further inboard and away from the drum. That way the hub can ride further onto the shaft taper without the need for shims.


With regard to truing hubs, not every hub we find is actually cost effective to restore. Some have seen a mechanic weld hub bolts, some have seen bearing races spin internally, and quite a few rear hubs have the bearing area out of spec. This is generally a taper in the race area, or the area is worn too much, ...or both. I have an aluminum plug that we place down inside the hub's race area. With your hand over the opposite side of the hub, you should be able to hear a 'pop' created from a vacuum when the plug is quickly pulled out of the hub. If not, the drum will not be in centerline with the brakes nor the axles.

Re: Hub Hardness and Cutting
 

I've installed many new brake drums but I've never trued the hub beforehand. What's the point? The drum is turned once the studs are riveted so they are true. Rarely do I have to take any more than about 0.010 - 0.015 at the deepest point to clean them up.
IMO, this is overkill on steroids.

Re: Hub Hardness and Cutting
 

Generally speaking, the hub flanges are bent 'proud' where the hub bolts were riveted onto the drum as this is a high pressure point. When you skim the hub flange just enough to flatten this area, you have a greater area of the hub flange concentrated over a larger brake drum flange surface. This should add to rigidity.

Is it overkill? I suppose it boils down to whether you are repairing or restoring. For me personally, I try to restore all assemblies back to factory specifications or tolerances first, and then replicate aesthetics. Not everyone shares that desire, ...and I totally get that.

Re: Hub Hardness and Cutting
 

Lots of the flanges get bent over the years. We take a small cleanup skim cut as needed before putting on new drums. If the hub bearing surface is a bit worn they get the sleeves and later style bearings.