Drums: Where to mount the lathe chuck?

B

bikemaniac

Senior Member
Hi,

When removing any ovality of the brake drums, what is the best place grab the drums with the lathe chuck? Maybe somebody has a picture?

Lucas
 
Search "The Restorer" or find the "How to Restore Your Model A" booklet with the same article by the late Bob Renz of Albuquerque. He shows how to do this in a lathe. 'Sorry. All my issues are packed away.
Marshall
 
The fronts are the same as modern drums but the rears require an adapter for the brake drum tool that inserts and locates off the the place the axle goes into the hub. Don't let someone remove the drums from the hub to turn them !!! It is difficult to find someone in Southern California, I can only imagine the problem you are going to have finding someone.

Charlie Stephens
 
I do the rears on my AMMCO machine with the small arbor no problem. I think it would be difficult to turn fronts or rears on a normal lathe. If you do try it make sure to wrap the drum with something to dampen the drum or you will get chattering.
 
How big of a lathe are you working with? As with any restoration project, fixturing often takes longer than the actual task. The key you are shooting for is concentricity in relation to the bearing race. Fabricating a mandrel that allows you to turn between centers would be the easiest way. Then use a boring bar to access the surface.

If you are experiencing chatter when cutting, you are either using the wrong speed or the wrong cutter tool.
 
Here is what I do. Rear brakes I cut about 8 inches off a scrap rear axle (with a useable thread on the taper). With a nut and washer this will pull down into the hub taper and project an inch or two out the back. Centre drill this stub both ends -nut end and bearing end.
For all sorts of unknown reasons my projection was not centred in the bearing housing. To hold it central and rigid I turned a lump of steel for a neat fit in the bearing housing and bored it to slide onto the stub of axle. Put this into the bearing before tightening the taper nut. Then mount the axle stub between centres, use a piece of key steel clamped to the axle nut and projecting between the jaws of the 3 jaw holding the headstock centre to drive the drum unit.(use a good small G clamp for this, ensuring it will not hit anything) Set speed to 30 or 40 rpm to avoid chatter. Or a higher speed and anti chatter strap. Take suitable cuts up to 0.010 or so as necessary, using a fine power feed. TC boring tips work fine. Make a nice radius at the inside end of the cut by judicious manipulation of both hand feeds.
Front brakes are much easier. Hold the outside of the hub by inside jaws just catching the parallel part of the hub outside the bearing cone (I am going from memory here), Use a live pipe centre inside the inner cone. Bore away as per above for rear hub. A tiny amount of herring-bone chatter causes no problem and soon dissapears under braking.
A good 3 jaw chuck is all you need for good brakes and one thousanth accuracy is not necessary. I do clock it all up inside the drum and push and pull it all about watching the dti for flex and movement to ensure rigidity before boring.
This description is long winded and pics would help, but I am on a phone and pics are elsewhere.
All this applies to my 5 foot DSG lathe without bothering to lock down the cross slide gibs. If I did and used a thicker boring bar I could use a lot more speed. As it is each surface took about 20 minutes with an 0.003 inch feed per rev. Too slow for a brake shop but fine for a hobbyist
I hope it helps. Once you have made the fittings you will be everyone's friend!
SAJ in NZ
 
Another thing about turning drums in a conventional engine lathe, It will tend to chatter a lot. You can eliminate some of this by wrapping a long rubber bungee around the outside as a vibration damper. Actually, It may be best to give them to a jobber, auto machine shop.
Terry
 
Terry said:
Another thing about turning drums in a conventional engine lathe, It will tend to chatter a lot. You can eliminate some of this by wrapping a long rubber bungee around the outside as a vibration damper. Actually, It may be best to give them to a jobber, auto machine shop.
Terry
Click to expand...

Terry, the biggest thing that causes that vibration chatter is too fast of surface speed, and not using a HSS tool w/ a negative rake cutter. The other issue is most Jobber Stores or Machine shops no longer have a brake lathe with a .750" arbor since a Model A, the early VW Beetle, and a few AMC products from the 50's are about all that need an arbor that small of size.
 
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