[Boatanchors] Restoring a vernier dial

[JAMES HANLON]

Dave,

You wrote:

I am really new to the art of restoring boat anchors and I need some
advice.  I have a National Velvet Vernier dial that is over 50 years old.
It turns smoothly, has no backlash and stays where I stop it.  My only
complaint or concern is it takes a fair amount of force to turn it.  It is
not one of those dials you may spin to reach the other end of the band!

The unit is a small one.  The dial front plate measures 3 7/8" by 2 3/4".
The tuning knob is not quite 1 1/2" in diameter.

A couple of questions.

What , if anything, should I spray into the insides of it to clean and
lubricate it?

2nd...  The chrome ring insert in the knob is rusted,  Any thoughts on how
to restore it?

3rd  The black crackle paint is worn off.  I suppose I can buy a spray can
of it to repaint after I sand it.  If so, which brand.

last ... The cardboard logging scale is in need of replacement.  Does
someone sell these, or should I get on the computer and attempt a
reproduction?

Thanks for any help that you may have for me.

73,

Dave, K4TO

What you have is a National MCN Dial and it uses an HRT-M knob.  It has a 5:1 Velvet Vernier drive mechanism.  The force that it takes to turn it is natural to this Velvet Vernier mechanism.  I have several of them from WW2 and later, and they have all been this way since I first acquired them in the early 50s.  I'd advise that you not spray your dial with any lubricant.

The full-sized HRT knob is 2 1/8" diameter.  The smaller HRT-M version is listed as 1 7/16" diameter.  I don't have any advice on restoring the chrome ring, I've never seen one that was rusted.  Maybe one of our Boatanchor chemists could offer some advice.  Or perhaps you could polish it smooth and paint it if you like.  There's a slim but non-zero chance that you may be able to find another HRT-M knob on ebay or one of the other trading sites.  It will usually accept a 1/4" shaft.  Likewise I don't have any great knowledge of black crackle paint.  I did touch up the panel of a BC-348 a few years back with some black crackle spray pain from my local hardware store and it worked satisfactorily, but the can is no longer on my shelf in the garage, so I can't recommend a brand.  Probably if you just get whatever is available it will be alright.

National went out of business a long time ago, so I doubt that you will find an original replacement for the scale.  The picture and description of the MCN dial in my 1952 ARRL Handbook show that it came with 3 calibrating scales (uncalibrated arcs) and a 0 to 100 logging scale.

The MCN is really quite a nice little dial and well worth restoring.  It will probably reward your efforts with many more years of good service.

73,
Jim, W8KGI