[Hammarlund] SP-600 original frequency dial disc repaint
rrkrr
rrkrr at comcast.net
Tue Jan 1 08:10:05 EST 2008
James,
Thanks very much for the info. Now I understand the reason for the
raised markings. This is probably quick and easy to do in an
established manufacturing process.
Bob K4ERR
James A. (Andy) Moorer wrote:
> 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
>
>
>
>
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