Any brake drum will have a diameter, reground or not.
Arcing is just a process that clamps the shoe in a jig, the radius is set to that of the drum, and fed into the sanding drum in an "arcing" motion; the surface of the shoe is skimmed off with a round drum sander.
I'm actually using my machine right now.
Did all 4 on a BN-4 last week.
Just tore down an MGA this morning for a major on the brakes.
If I have to do the shoes on it, I'll try to get a little video.
: Arcing brakes is an old process that was
: much more common when 1) cars had
: 4-wheel drum brakes, 2) was more common
: when shoes were relined rather than
: replaced, and 3) was pretty much phased
: out when shoe linings became bonded and
: asbestos was identified as a health
: issue. I have an acquaintance who
: learned the process in trade school 35+
: years ago but never actually used what
: he learned.
: Regardless, the goal is to get a much
: better fit between the shoe lining
: material and the inside of the drum.
: The idea is simply to maximize the
: contact area to get the most stopping
: power. I am willing to give it a try
: on this brake job if I can do it at
: home by improvising. If the fit is
: pretty good to start with I won't do
: Doug L.
: --Previous Message--
: So what's the deal with arcing the
: I've never heard of this before. I've
: recently put new shoes on mine.