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Dear all
I am quite new in this forum and I would appreciate your help.
I am driving a 43 Dodge WC 51, restored condition. But there are still things to do.
My brake drums are not round inside and must be machined, principally no problem.
The question is, does anybody have experience how to set up the drum in the machine without damaging it?
Thanks in advance, Michael

G,Day Michael .The drums should be done on a lath in a brake workshop. It sounds like your drum,s are out of round . Don,t know if they can be re rounded.If you look at the outer/inner edger of the brake drum there is a chamfer ,approx 1- 2 mm . If it is not there your drums might be over size . You can get away with o/s drums by making the shoes {Lining,s } a bit thicker . Also if there are big score marks in the brake drums tell the bloke that is machining your shoes to leave the the deepest score marks in . Other wise they will machine them down and you will have to look around for new drums . A few deep score marks will not have much effect on your trucks braking. I don,t know if new brake drums are available .The more they take of the less life you will have left in your brake drum,s . Ray

The answer to the specific question you ask is that the drum is left mounted on the hub and the bearing outer races or cups are left in place. There are a series of tapered sleeves that are provided in increments so as you will have what is required to support the hub on the bearing outer races. This ensures that the drums are machined true to the bearings which is the critical factor.
That is the way it was done years ago from what I recall. I doubt they've changed.

David

Thanks Ray and David
But I don’t understand the matter of the sleeves. Maybe my English.
I thought that, when they mass produced the drums, they took the inner bore as reference to turn the braking surface on the machine. And this inner bore is also adjusting the drum on the outer diameter of the hub. Am I wrong?
Cheers Michael

Mass production is different to maintenance. In mass production you are dealing with a large number of identical components. In maintenance you have to deal with small numbers but a wide variety and so the need for adaptor sleeves. Drum machining is not done on a standard lathe it is done on a specialised machine dedicated to that purpose.
Take your drums/hubs/bearings to a professional.
As Ray stated, the job should be done in a brake workshop.

David

Gutten Tag Michael,
the only way to acurately machine your brake drums is with the drum installed on the hub. The inner races of the wheel bearings act as the alignment on the spindle of the machine (as they do on your truck). this ensures that once machined the drums are perfectly aligned to the axle and therefore your brake shoes.

DO not try to machine the drums with out being installed on the hub.

Ignore the "mass procuded" thoughts. Mass production simply means each part is within preset specifications. It does not translate to perfection each time and it is particularly true in the case of brake drums.

Cheers

Ian

LIke the others have said machine drum when attached to the hub. A new drum measures 14.125". The max amount you can machine them too before you need new drums or oversize shoes is 14.215". at that point though is is recommended to replace them. if you buy replacement drums that are used, buy them with the hubs. if you buy brand new drums they need to be installed on your hubs then machined.
This is still true on modern truck with disk brakes when replacing rotors.