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CGEM clutch knobs are stainless steel. Unpaint them!

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14 replies to this topic

#1 Michael Covington

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Posted 22 July 2019 - 08:27 PM

The black paint was scuffing off the clutch knobs of my CGEM, and I wanted the knobs to be more visible anyhow, so a couple of years ago I repainted them, with poor results.  I decided the first coat of paint must be loose and all the paint should be stripped off.  So I gave them 24 hours in a jar of paint thinner, followed by a lot of wire-brushing, and made a discovery...

They are not aluminum.  Nor are they ordinary steel.  They are a slightly warm-colored non-magnetic metal whose density is about 7.5 g/mL (my own rough measurement).  

They must be stainless steel, which is notoriously hard to paint.  I wire-brushed them thoroughly; followed up with a small, fast wire brush on a Dremel; and then polished with a buffing wheel.  They became as shiny as chromed motorcycle parts.  The best paint is no paint!

 

20190722-knob-in-situ.jpg


Edited by Michael Covington, 22 July 2019 - 08:31 PM.

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#2 OldManSky

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Posted 22 July 2019 - 08:30 PM

They look great that way.  And you were going to paint them white so they'd be visible...! :)


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#3 Michael Covington

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Posted 22 July 2019 - 08:43 PM

Next trick is to see if the knobs on my AVX are the same.  It may be about to go with me on an observing trip, though, so I won't do that immediately.  It would be inconvenient to get to the observing field and realize the knobs were still soaking in paint thinner at home :)


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#4 Scott in NC

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Posted 22 July 2019 - 09:39 PM

Nice!  Now they're not only much more visible, but IMO look way more attractive than if they were painted.  Great discovery, Michael! :waytogo:


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#5 Neptune

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Posted 22 July 2019 - 09:55 PM

Beautiful and  functional what more could you ask for. 


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#6 Michael Covington

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Posted 22 July 2019 - 10:00 PM

I'm tempted to get in touch with a Celestron engineer I know -- I wonder if even Celestron knew about this!  They are probably contract-manufactured in China and the materials are only loosely specified.

Before I do that I'll do my AVX and see if the knobs are the same material.  I think they are.



#7 TikiTom

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Posted 22 July 2019 - 10:00 PM

You may have some special knobs there. 

 

The knobs from my CGEM are kinda chewed up from the previous owner using pliers to tighten them and they look like cast aluminum metal under the missing paint and the 'bite' marks....


Edited by TikiTom, 22 July 2019 - 10:04 PM.


#8 Michael Covington

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Posted 22 July 2019 - 10:23 PM

Mine look cast, which is why I'm not 100% sure they're stainless steel, but I can't match them to anything else -- maybe someone who knows more about metallurgy will come along.  Cast stainless steel certainly does exist.  If they tarnish, I'll reconsider painting them or at least clearcoating them.

 

If they're not stainless steel, what are they?  


Edited by Michael Covington, 22 July 2019 - 10:25 PM.


#9 Michael Covington

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Posted 22 July 2019 - 10:34 PM

I'm no metallurgist, but looking around the Web, I see that cast stainless steel is common in China, and they have cheap grades of it that we don't.  Some of them are not actually stainless.  We will see if my knobs tarnish...



#10 TikiTom

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Posted 23 July 2019 - 10:31 AM

Mine look cast, which is why I'm not 100% sure they're stainless steel, but I can't match them to anything else -- maybe someone who knows more about metallurgy will come along.  Cast stainless steel certainly does exist.  If they tarnish, I'll reconsider painting them or at least clearcoating them.

 

If they're not stainless steel, what are they?  

Whatever they are made of, they sure do look nice all shined up. 

 

Mine are really chewed up, so I replaced them w/ the ADM versions....



#11 gregj888

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Posted 24 July 2019 - 10:07 AM

Carefull with the wire brush on stainless.  Get a stainless brush if you can.  Steel brushes can leave bits of steel in the part and those bits can rust effecting the finish.


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#12 Michael Covington

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Posted 25 July 2019 - 10:21 AM

Now I can confirm that the AVX knobs are the same way.  Mine didn't polish up quite as well, but they look better polished than painted.



#13 dcollier

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Posted 26 July 2019 - 07:04 AM

These knobs are notoriously hard to properly tighten.  Hence the comment of someone using pliers.  I have replaced mine with ADM clutch levers.  No More slipping clutches.  Easy to tighten.

 

https://www.admacces...utch-lever-kit/



#14 Michael Covington

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Posted 26 July 2019 - 08:39 AM

I never had any trouble tightening mine.  If they seem to require undue force, I'd check what is going on inside the clutch.



#15 starman876

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Posted 26 July 2019 - 01:58 PM

These knobs are notoriously hard to properly tighten.  Hence the comment of someone using pliers.  I have replaced mine with ADM clutch levers.  No More slipping clutches.  Easy to tighten.

 

https://www.admacces...utch-lever-kit/

I like the way those levers lookwaytogo.gif




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