Machining Buick finned drums

I know this has been posted about many times, but without specifics needed. I don't have a lathe in my garage, so I need to take the drums to a shop with specific instructions on what to do.

I know the 45 fin Buick drums with Lincoln (2" wide shoe M/T) brake plates require machining the OD lip of the drum (both iron and aluminum) to clear the back plates. How much has to be taken off, and where? Reports vary. The drums I have (on '46 front hubs) were supposedly set up already for this, but still hit the backing plates. Both the inner iron liner and supporting aluminum have been machined down to about 1/8 inch above the outer as-cast surface that supports the fin ring.

Does a grove need to be machined still further BELOW that as-cast surface? How deep and how wide? Does such a grove cut into both the aluminum and iron?

The attached image from a older tech seems to show this.

Steve

 

i usually leave the cast iron liner alone , and cut that aluminum out down to the bottom of the groove. then give it a try.....cut more if you need to

 

^ Yeah you don't need to touch the liner. Just eliminate the aluminum lip on the top side of the liner down to where it's level with the rest of the aluminum, if that makes sense. It's really clear when you hold the backing plate up against the drum..

 

Not really adding much to the thread other than asking for clarification as I will need to be looking at this myself soon.

Do you mean remove the metal indicated on the EXPERTLY edited image?

 

no! the aluminum right on the cast iron liner

 

Sorry, decided to be more helpful and go take some photos of my set to see if this helps.

Matching the drum to the backing plate, the plate rests where the small Xs are on the first photo. So, the part to be removed is highlighted and buts up to the bit where the Xs are.

Hopefully this is helping the OP.

 

that's it!

 

Many thanks 36-3window. To help the OP check out this link and specifically post #13.

http://www.jalopyjournal.com/forum/showthread.php?t=782579

This is a magazine article walking you through the process. Seems painless.

 

I had my machine shop take a total of 0.620 out of the drum edge for it to fit with no rubbing. See pictures below I did use the same set up with the 48 lincoln rear backing plates this is the reason why we had to trim so much from the drums.

Frenchy