[R-390] Painting Knobs

[Bob Camp]

Hi

The “cheap” approach to cleaning up something like this is a vibratory system. They get used for a lot of things, including polishing brass collected from your local range. They come in all sorts of sizes. 

The trick is picking the correct media to use for the material and “crud”. It’s not always obvious what that might be. It could be anything from corn cob chunks right through weird shaped ceramic pieces. Some level of research (and possibly experimentation) will always be involved. 

Once you have it set up, you toss in a knob or lots of knobs (depending on how big the machine is). Fire it up and come back in hours / days. Maybe switch out the media and run it with something else for a while. 

No, it’s not fast, but it does get the job done. There also isn’t a lot of hand labor involved.

Fun !!!

Bob

> On Aug 12, 2024, at 11:38 AM, Barry <n4buq at knology.net> wrote:
> 
> Tom, 
> 
> I really wish I had glass bead or other media blasting available. That would have saved me so much time! 
> 
> After getting as much of the existing paint as I could with Aircraft Paint Remover, I resorted to hand-sanding with 320-grit silicon carbide paper. That left a shiny but not too slick of a finish. I really don't know why the primer didn't stick to it. 
> 
> I went with full gloss and not sure if that was the best choice (I don't remember what sheen I used long ago) but it looks okay. If this paint job does fail with use, then at least it's easy enough to remove... 
> 
> Thanks again, 
> Barry - N4BUQ 
> 
>> Barry,
> 
>> I have done several sets and just finished up one the other week. I used to wire
>> wheel the old paint of but have since transitioned to using my glass bead
>> cabinet. This provides a little "texture" for the paint to grip to but not
>> enough to show through to the finished coat.
> 
>> I have also used the self etching primer with good results. For the last two
>> sets I used Rustoleum semi gloss / primer in one. This worked well also.
> 
>> Tom
>> W3TA
> 
>> On Monday, August 12, 2024 at 10:13:31 AM EDT, Barry <n4buq at knology.net> wrote:
> 
>> As I've mentioned over the past several months, I'm in the process of
>> refinishing the knobs (as well as all the other front-panel parts) for my R390.
>> I stripped, sanded them and used Rust-Oleum Self-Etching primer and painted
>> them with Rust-Oleum enamel.
> 
>> The Rust-Oleum Self-Etching primer and Rust-Oleum enamel worked very well on the
>> front panel, escutcheon, meter covers and, as far as I know, the large knobs. I
>> had reason to remove the paint (again) on the larger knobs and the paint and
>> primer stuck quite well; however, I've discovered that the primer doesn't seem
>> to stick very well to the smaller knobs.
> 
>> While working on the smaller knobs, I noticed a small chip in the paint on one
>> of them that exposed the bare metal. I don't know exactly how that chip was
>> made but I think I dropped one of the knobs onto the table top which might have
>> hit it just right. I noticed I could take a sharp putty knife and some of the
>> surrounding paint could be removed all too easily. Another knob had a very
>> small spot where the bare metal was exposed as well.
> 
>> I decided to dump those two (and a third one that had some small defects in the
>> top coat) into a can with acetone and, after a short soak, I pulled them out.
>> The paint had wrinkled quite well and was very easy to remove (it virtually
>> fell off); however, the primer also came off very easily which was different
>> than some of the other pieces I'd painted. In fact, the primer and paint stuck
>> very well to each other but the entire paint/primer fell away from the metal.
> 
>> I think those knobs are die-cast aluminum so I can't explain how/why the primer
>> wouldn't have stuck to those the same way as the other aluminum parts but I
>> just don't know.
> 
>> Anyone have a similar experience and, perhaps, have a suggestion for a better
>> primer? I think the factory used conversion (Alodine?) process on most all of
>> the aluminum parts and that would probably be a "best" solution. I had some
>> parts done that way many years ago around here but it was pretty expensive and
>> I'm not sure it's even still an option around here.
> 
>> Thanks,
>> Barry - N4BUQ
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