Packard Forum Index » Post-War (1946-54)

When mounting a drum on a brake lathe, should the wheel bearings be removed?

I would think so; you wouldn't want all the metal particales getting into your bearings.

I believe that they are removed.

Cause not only roundness.

But all that grinding would get in the bearing

When I was doing such things, I remember for both bearings all of the elements, that is, inner race, rolling elements, and cage, are removed as two independent assemblies. Both outer races are left installed in the hub. After turning the hub is thoroughly cleaned before the, now repacked, bearings are installed, followed by the seal.

dp

The adapters on a brake lathe are designed to seat in the cones of the bearing outer races, so leave them in. You can wash and pack the bearings while the lathe is running to pass the time. As David says, just wipe everything out well when you are done.

Many thanks for the info. I have sent two different sets of front drums to two different local shops to cut. One pair has a soft pulse, and the other a rather violent machine gun like shudder. When adjusting the shoes I cannot get a nice swish, but rather a grab and release, as I would expect with an out of round drum.
In both sets I left the bearing races in the drums as you guys indicate. Just searching for reasons why I can't seem to get at least one set round.
Neither set has been cut beyond spec. So, I am just searching for an answer. Thanks again, you guys are great.

Not all brake lathes are created equal. Like any equipment there are high and low end machines. Having turned many drums on different machines in my life time I have also seen operator abuse.If you can find one that grinds rather than cuts you will have a superior job done. In this age of throw away it has become harder to find to qualified machinist, But dont give up.They are out there.

To add to my last suggestion. Sometimes the drum may be loose on the hub. To overcome this put the wheel bolts with spacers on to hold the drum tight on the hub

Look at the surfaces and see if poorly machined/have "chatter". Lay a straight edge across on quadrants. Shine a light behind. Shouldn't be any coming through.
You can take a suitable inside caliper and measure for roundness.
I'd take them back, if I wasn't satisfied.
Like they say, this used to be common, but not so now. Many parts places don't even have a drum machine any more.
If they know how to run the machine they would know if the bearing needed removed or not.
I don't really recall, I haven't had a drum turned for ~4 decades now, rotors not even much. New ones are as cheap but not for "P"s. I'm pretty sure watching my friend at NAPA, too long ago, the race stays to fit/center the drive end. But I wouldn't bet anything on my memory.

Drum turning machines are crude compared to an engine lathe. Often the mechanic will assume that the drum is running true after he mounts it.That isnt always the case. Im a retired master machinist, and I always turned my own on a regular engine lathe. They should be checked with a dial indicator before cutting. If the new machined surface is eccentric relative to the bearing race, it would cause the condition that you describe.