View Full Version : Brake drum Machining

08-21-2009, 04:34 AM
Has any one made or used a jig for holding brake drums while they are machined? We bought a 1960 Morris Minor last week and I made a shaft up with a spigot on it to bolt the brake drums to for machining, assuming the centres were all the same size, got the first one done, then the next one didn't fit, neither did the next and the last one had a hole about 30 thou smaller again! Turned out that the second and third were the same size so I turned down the spigot to suit, the third drum I packed out on the spigot, trued it up and bored its centre to suit the spigot, then turned it around and bolted it up and bored it. There must be an easier way does anyone know it?

John Stevenson
08-21-2009, 04:53 AM
On some of the cheaper stuff that has these tin flanges cast into the drum I bolt to the faceplate with a big packer to try to beef them up and stop the vibration.

Used to do loads but on modern vehicles it's cheaper to buy new drums if they are anything like worn.

Doesn't apply to vintage vehicles as much but I don't get as many as I used to.

Did 3 drums last week for a vintage Alvis, two were just a lick and polish with emery cloth but one needed a skim as the lining had come off and the alloy shoe had welded itself to the drum in big smears.

Drum was still good, it was stuck on and not gouged out.
Problem with these are they are only 2" deep but 15" diameter and running at anything over 27 revs leaves vibration marks even with 3 leather belts strapped round them.

Once the chatter starts it's hells own to get it out and the next cut just picks up on the existing marks and repeats it.
Trick is to work from the inside out because the inside corner is the strongest, most supported point and if you can start off with a good cut, chances are it will stay good.
Another bonus is you are working out into fresh air so you can safely leave it to trundle on without a wreck at the end :rolleyes:


08-21-2009, 04:54 AM
I use a three jaw chuck :D

They usually ring like crazy, if so I wrap some rubber around the outside to dampen them...You can usually get rubber strips from places like clark rubber, then you have some rubber on hand to cut washers out of to fix leaking taps.. :)

08-21-2009, 05:48 AM
The trick for reducing the chatter is to use some stick on wheel weights spaced around the drum and then wrap it with a belt or just electrical tape.

A 1960 Morris Minus? That was my first car. I feel your pain. :D

08-21-2009, 07:28 AM
Too far from the nearest trustworthy brake shop Will? I'm lucky that Darren is just across town.
Replicate the brake lathe with a Threaded shaft (An old axle should be good.), a large cup with 5 fingers or so(for the rear of the drum), a cone,(for the front of the drum), some spacers and a nut. Use the heaviest boring bar you have or make a purpose one and as John suggested, bore from the inside out -- slow revs slow feed. Everything as rigid as possible.

08-21-2009, 08:32 AM
'60 Moggie? Wish I still had mine:


Ground up resto-mod with all 1275 cc Spridget driveline with Sprint cam, twin 1 1/2" SU's, tube headers, disc brakes in the front, tube shocks in the rear, 13" Minilite wheels with fat tires instead of the stock bicycle tires, Austin America bucket seats, E-Type Jag speedo, (optimistic, eh?) MG Blaze Orange paint. The pic is 35 yrs old.

08-21-2009, 09:41 AM
And did yer keep the "Trick" original front suspension?? :rolleyes:

Regards Ian.

08-21-2009, 10:20 AM
Speedy has it. I have done the same as you. I messed and messed with trying to true up a brake drum on my lathe and it took a while. Now since, I have been given a drum rotor lathe but..... here is what I did.

Use the biggest threaded rod that you can get and will fit through the drum. Chuck it up in the lathe. Next put on the 5 point support as Speedy noted. Next put on the drum and then a cone that will keep the drum centered up. The cone makes up for differences in drum location bore. Next a nut to hold the cone into the drum.

Finally find the largest boring bar that you can and lock that thing on the cross slide as rigidly as you can. Dont hang any more bar out than you have to. And If you have a thick heavy rubber band, wrap that thing around the outside of the drum to keep the vibrations down. Or as Evan noted stick on wheel weights can work as well.

Dont turn the drum larger than spec. Same with rotors. I finish my work by running a scotch bright type pad in a little angle grinder and buff the surface to knock any record groove sharpness down. If you do it right this sharpness will be minimal anyway.

I'll try to see if I can get a photo to post.

Good luck rock~

08-21-2009, 11:17 AM
And did yer keep the "Trick" original front suspension?Oh he11 yes! Torsion bars: OK. Brass (or was it bronze?) lower trunnion/swivels: not so good. Armstrong lever shocks; bad! I got 'em working a little better after experimenting with the internal valving and different grades of Bel-Ray motocross fork oil.

A front anti-sway bar off of some long forgotten european car helped a bit along with a homemade rear panhard rod as well.

Doc Nickel
08-21-2009, 02:58 PM
How to turn a brake drum? I put it in my Ammco 3000 brake lathe, of course. :D

Does a lovely job, but takes up way too much space for as often as I use it...


08-21-2009, 03:08 PM
How to turn a brake drum? I put it in my Ammco 3000 brake lathe, of course. :D

Does a lovely job, but takes up way too much space for as often as I use it...

Yabut...worth it. I won't even turn them on my lathe. I took my last set of rotors to the local auto parts and let them do it...the mess is awful. It's not the cast iron, but the iron oxide, brake dust...plus the awful hard burnished surface. A dedicated machine deals with this crap well.

On the other hand, the last set I took in, one of the goobers there must have had a swarf piece under the arbor it was mounted on. Went in straight and came back turned lop-sided or something as they pulse like they were warped. Didn't have time to deal with it at the time and now I figure they would laugh if I asked them to re-turn them two years later. It's hard to get good help.