[Hammarlund] SP-600 original frequency dial disc repaint

[James A. (Andy) Moorer]

Below are a couple of notes from Miles Anderson, K2CBY, who addressed the 
issue. I have been meaning to post these on the Hammarlund history web site 
but sorta never get around to it:

This will tell you more than you ever wanted to know about this particular 
subject.

James A. (Andy) Moorer
www.jamminpower.com


----- Original Message ----- 
From: "rrkrr" <rrkrr at comcast.net>
To: <Hammarlund at mailman.qth.net>
Sent: Monday, December 31, 2007 10:23 AM
Subject: [Hammarlund] SP-600 original frequency dial disc repaint


> Has anyone figured out how to repaint the original frequency dials on an 
> SP-600?  How was this done in the first place?  The discs are brass and 
> the dial numbers and reference markings are raised, ever so slightly, 
> above the background.  I'm guessing that the original dials were first 
> painted entirely white and then pressed face first against a (very) flat 
> metal plate that had been "inked" with black paint - much like inking the 
> type on an old printing press.  Has anyone tried this?  Better yet, is 
> there anyone out there doing this as a service?
>
> Bob K4ERR

================================================================
Note 1: 3/4/07

I thought I'd bring you up to date on the status of my SP-600 rebuild, on
which you were kind enough to answer my questions a few weeks ago.

The (formerly) white paint on both the Megacycle dial and the Bandswitch
dial had flaked to the point that they were an embarassment. Rather than use
paper dial overlays, I decided to try for a restoration of the originals,
using some of the techniques I had acquired as a 1/72 scale plastic airplane
model-builder.

I stripped the original white paint off both dials with acetone, using an
old toothbrush to get in the areas inside the letters.

Interestingly, the original black lettering remained intact. This leads me
to believe that the black finish is not paint, since acetone didn't touch
it.

I then spray painted both dials with white Krylon fast-dry enamel. (In
retrospect this was not a good idea since the Krylon goes on quite heavy and
is hard to control. I would have been better advised to airbrush several
thin coats of Testors hobby enamel.)

I oven dried the dials at 150 to 175 degrees F. for about 90 minutes.

I then went over all of the raised lettering with a 400 grit hobby sanding
stick. (This is a hard plastic wand about 5 inches long and about 1/4 inch
square. One end is spring loaded. A continuous belt of emery cloth 1/4 inch
wide is stretched over it.) If you are careful, you can sand off just the
white paint, leaving the raised lettering its original black color. (Finer
grit would have been better but so far as I know 400 is the finest grit
available in the sanding belts.)

(An alternative might be to glue 600 grit wet or dry paper to a flat surface
with rubber cement and rub the dial against it, pressing uniformly from the
rear.)

Inevitably you will remove some of the blacking from the raised letters but
being careful I held the "shiny brass" to about 10% of all the raised
surfaces.

Here is the innovation. I coated the exposed raised lettering with an acid
preparation called "Blacken-it" that model railroaders use. I applied it to
the dial with a Q-tip. The white paint and the existing blacking mask
everything but the raised letters that had been scraped down to shiny brass.
With as little as 5 minutes time and a definite minimum of work the
Blacken-it turns the exposed brass a shade of black that matches the
original finish and texture perfectly. (This leads me to suspect that I am
very close to duplicating Hammarlund's factory process.)

I had dinged the white paint at a few spots, and I touched these up with a
brush.

Finally, I coated the whole thing with Ace Hardware's satin finish acrylic
spray. This not only served to protect things, but the finish yellows over
time and it should eventually match the bandspread dial that did not require
refinishing.

The sanding sticks, belts and "Blacken it" are available from an on-line
hobby outfit called www.micromark.com.

Miles Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, NY 11963
k2cby at optonline.net

================================================================
Note 2: 3/7/07

First, a correction is in order. In the original post I recommended
overspraying with Ace Hardware satin urethane acrylic. That worked fine for
the first coat. But the second coat caused all the underlying white to
alligator. Unless you are aiming for a wrinkle finish dial, this step should
be omitted!

I wound up starting over again (obsessive-compulsive disorder). This time I
airbrushed Testors Model Master enamel hobby paint. It went on much better
than the Krylon spray.

For the paint removal process, this time I laid a sheet of 600 grit wet or
dry sandpaper on a flat desk top with the edge of the sandpaper flush
against the edge of the desk. Holding the sandpaper taut with one hand
(better to have glued it down) and the dial with the other, I stroked the
dial against the sandpaper, exposing about half the dial at a time and
applying a light but even pressure. It worked like a charm.

I followed the blacking process described below and then decided to quit
while I was ahead and not try to overcoat the finished dial

Yare welcome to post the tip. Rewritten in light of experience it
should read as follows:

The (formerly) white paint on both the Megacycle dial and the Bandswitch
dial of my SP-600 had flaked to the point that they were an embarassment.
Rather than use paper or plastic dial overlays, I decided to try for a
restoration of the originals, using some of the techniques I had acquired as
a 1/72 scale plastic airplane model-builder.

I stripped the original white paint off both dials with acetone, using an
old toothbrush to get in the areas inside the letters. The original black
lettering remained intact. This led me to believe that the black finish is
not paint, since acetone didn't touch it.

I painted both dials with white Testors Model Master enamel hobby paint
using an airbrish. (Spray can enamel is an alternative, but it goes on quite
heavy and is hard to control.)

I oven dried the dials at 150 to 175 degrees F. for about 90 minutes.

The next step is to remove the paint from the raised letters. There are two
ways to do it. The second method is much faster but it removes more of the
original blacking on the raised lettering:

(1) Go over all of the raised lettering with a 400 grit hobby sanding stick.
(This is a hard plastic wand about 5 inches long and about 1/4 inch square.
One end is spring loaded. A continuous belt of emery cloth 1/4 inch wide is
stretched over it.) If you are careful, you can sand off just the white
paint, leaving the raised lettering its original black color. (Finer grit
would have been better but so far as I know 400 is the finest grit available
in the sanding belts.)

OR

(2) Attach a sheet of 600 grit wet or dry sandpaper to a flat surface with
rubber cement with the edge of the sandpaper flush against the edge of the
surface. Holding the dial by hand, stroke the dial against the sandpaper,
exposing about half the dial at a time and applying a light but even
pressure. Continue rotating the dial until all the lettering has been sanded
clear of white paint.

Inevitably you will remove some of the blacking from the raised letters but
being careful I was able to hold the "shiny brass" to about 10% of all the
raised surfaces.

Here is the innovation. I coated the exposed raised lettering with an acid
preparation called "Blacken-it" that model railroaders use. I applied it to
the dial with a Q-tip. The white paint and the existing blacking mask
everything but the raised letters that had been scraped down to shiny brass.

With as little as 5 minutes time and a definite minimum of work the
Blacken-it turns the exposed brass a shade of black that matches the
original finish and texture perfectly. (This leads me to suspect that I am
very close to duplicating Hammarlund's factory process.)

The sanding sticks, belts and "Blacken it" are available from an on-line
hobby outfit called www.micromark.com.

Miles Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, NY 11963
k2cby at optonline.net