Skimming a wheel hub brake drum surface

[canuck750]

I have a pair of Benelli 650 Tornado hubs that have some significant wear in the brake drum surface. I sued the axle, spacer and nut to secure the hub into the chuck, my 6" chuck does not have reversible teeth and I could not figure out how else to hold the hub in the lathe, probably a bodge way to do things, appologies to the professionals out there.



I am not a machinist  and have no idea how much of the drum surface can be skimmed. I cut a couple thou off the grooved drum surface and left it at that.
I know its not good practice to skim a hub but these were in real bad shape.



There are still some small grooves in the drum face but I am reluctant to go any further.

How much is too much?

[Chuck in Indiana]

Looks like a practical solution to me. A couple of thou though? That ain't squat.

[canuck750]

Thanks Chuck,

Jim

[toolittletime]

Looks like a practical solution to me. A couple of thou though? That ain't squat.

 :1:

[Huzo]

I have to confess to a bit of embarrassment giving you advice Canuck, but here goes...
You will have a lot of trouble getting the drum to spin with the axle remaining in line by regular chuck mounting.
It is possible to get it into a chuck and put a clock on it, but that is not the best way.
The real solution is to put the axle in the lathe and put a small centre in each end. The axle can then be placed between centres in the lathe with the drum spinning on its own axle. It will need to be dogged so as to be able to be driven.
Needless to say, if you do not do it this way, you will almost certainly have a few thou of run out, and the lever will pulse like buggery.
Chuck suggests that a couple of thousand is acceptable, but I'd wager that 1/2" of lever travel equates to something like that amount at the shoes, so conversely, if you are out by 2 thou' the lever will move considerably in use.
No bloody good...

[canuck750]

I have to confess to a bit of embarrassment giving you advice Canuck, but here goes...
You will have a lot of trouble getting the drum to spin with the axle remaining in line by regular chuck mounting.
It is possible to get it into a chuck and put a clock on it, but that is not the best way.
The real solution is to put the axle in the lathe and put a small centre in each end. The axle can then be placed between centres in the lathe with the drum spinning on its own axle. It will need to be dogged so as to be able to be driven.
Needless to say, if you do not do it this way, you will almost certainly have a few thou of run out, and the lever will pulse like buggery.
Chuck suggests that a couple of thousand is acceptable, but I'd wager that 1/2" of lever travel equates to something like that amount at the shoes, so conversely, if you are out by 2 thou' the lever will move considerably in use.
No bloody good...

Good advice

I will give that a try

[Huzo]

If you put a rolling centre in the headstock and a dead centre in the tailstock, you'll be able to spin the drum on it's own races.
That WILL work..

[Rough Edge racing]

 Sometimes, at least in the world of older British bikes, a round brake drum often goes out of round after building the wheel . Sometimes it's because the spokes were over tightened...Getting a built spoke wheel brake drum cut  requires a big lathe or jigged on a mill of some sort..
 I'm an untrained machinist who does all sorts of stuff with the wrong tooling....You do need to support the mandrel at both ends..

[Sheepdog]

I have seen maximum drum diameters posted on the drums on some brakes...I guess so technicians are aware of the safe limit. Or maybe it is posted in the owner�s manual...

[Don G]

Rough Edge is correct, the wheel should be assembled then the drum trued, find an auto repair shop with a brake drum lathe, I have an old Bear unit that I regularly turn motorcycle drums on, even with the tire mounted. DonG

[Antietam Classic Cycle]

Rough Edge is correct, the wheel should be assembled then the drum trued, find an auto repair shop with a brake drum lathe, I have an old Bear unit that I regularly turn motorcycle drums on, even with the tire mounted. DonG

 :1:

[neverquit]

I have some experience with these things and I am impressed with the comments and suggestions that have been posted.  There are lots of knowledgeable and intelligent people on this forum.  My suggestion is simple, since you have already done it, lace the wheel back up and very carefully try it.  Once the wheel is mounted on the bike you can put it up on a stand of some sort and spin the wheel while gradually applying brake pressure to detect any obvious defects before an actual road test.

[Sheepdog]

 I just checked my ‘71 Triumph shop manual. It states, “Do not skim more than .010 in. from the drum. If the diameter exceeds more than given in the GENERAL DATA (the maintenance/rebuild data in the front of the manual) by more than .010 in. the drum should be renewed.” I expect this isn’t far off of the Benelli spec...