Hi John ~
I take it that the platter is already off or at least removable at this point,
and the platter itself isn’t level with the hub?
My approach, one of any number of ways that people might come up with, but this
is what comes to mind, would be to fabricate a temporary substitute
spindle/arbor that passes fully through the hub spindle socket, perhaps with
about four inches of substitute arbor exposed on both sides of the platter.
This is not meant to be used in the phonograph but just for straightening the
platter. To make it a precise fit, both for truing purposes and to avoid hub
socket damage, duplicate any taper in the original spindle, onto the new turned
arbor. You’ll also need to replicate the cross pin if there is one, so the
platter can lock onto the substitute arbor. Come to think of it, this might be
necessary if your fit is otherwise precise.
WORK HOLDING: Ideally, a decent sized lathe, say 6” to 10” (“ is max diameter
of what the lathe can turn), with a three or four jaw chuck in the headstock
and a Jacob’s chuck in the tailstock, each chuck securely tightened on your
substitute arbor. You can use the lathe’s own tool post or any kind of fixture
to gauge the deviation of the warp in the platter as you HAND turn the
arrangement. This will show you clearly where the platter is high or low, and
how far from true it is. With the substitute spindle, securely held providing a
rigid mass to work against, you can then more accurately manage how far you
push the platter, and where to push it. If necessary you can make a large clamp
from a piece of 4” x 4” x 3/4" thick wood (to press against the underside of
the platter), and a similar piece to clamp to the platter surface, which in
turn can be clamped together, sandwiching the platter tightly, with a large
carpenter’s clamp, which will also afford you a convenient handle to make your
Don’t overdo it. Mark the platter edge with a sharpie or chalk (easily
removable), at the approximate limits of where the distortion appear to be, so
if you have to adjust the clamp and try again, you don’t lose track of where
you’ve been. You can mark 1, 2, 3, etc., for each adjustment. You’ll be hand
turning the platter & substitute spindle several times, probably before you get
it where it needs to be. It also takes some keen observation to decide whether
you’re pulling the platter up from or down in relation to the hub. If you get
it wrong, don’t worry, as long as your end result is true.
The point is, you have to work against mass and have a way to control your
manipulations. You may find that moderate heat helps, but be careful not to
overdo it or you can have the project go drastically wrong. The idea of a tack
weld isn’t unreasonable, but you end up with something that’s far from factory
condition, and if it’s otherwise a nice machine, a detractor.
Regarding Harvey’s recommendations for freeing a stuck platter, I would add
that PB Blaster has always worked better for me than Liquid Wrench or any other
penetrating oil product. I would recommend also not to use a steel hammer, but
a sufficiently heavy brass one, or a hard plastic mallet. Otherwise you risk
getting a flat spot on your spindle top. An alternative would be to place a
piece of hardwood over the spindle before you whack it. Harvey’s recommendation
to support each side and hold it under tension is good.
If you don’t have the means to do the warp repair yourself, share this
recommendation with a machinist that you can trust, and see what they think.
They may have a better idea.
Best of luck keeping another worthy phonograph in good shape,
On Dec 8, 2016, at 4:15 PM, John Selph via Phono-L <firstname.lastname@example.org> wrote:
> Anyone know of a way to repair a “sprung” platter? Apparently someone
> attempted to remove the platter on a VV 1-1 by prying and the platter is now
> warped. I was thinking of possibly using a press to apply pressure and
> placing a tack weld on the “high” side of the platter/hub connection. Would
> this work?
> "Once in the wilds of Afghanistan I lost my corkscrew, and we were forced to
> live on nothing but food and water for days." W. C. Fields
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