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Cave-Astrola 8" f/7 Model B Deluxe restoration / upgrade

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#51 Dave Cook

Dave Cook

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Posted Yesterday, 11:13 PM

Whew!  Did all the tube polishing this afternoon.  I went through the #34, 36 and 38 polishes with the matching foam pads on the Bosch orbital sander.  It's REALLY glossy now - check out the reflected things in the photo (click to zoom in).  This process took up some of the first plus most of the 2nd playoff game (yeah I'm the one who doesn't watch much football around here!). Next up will be putting Black 2.0 on the inside of the tube, and then onto installing the inner rotating rings.
 
Shiny tube after polishing
 
On a slightly related note, I designed and printed a rack for imperial T-handle hex keys.  When you're a home machinist with Chinese equipment everything is metric, but the Astrola project has caused sudden high use of imperial hex wrenches.  All I had were loose L-shaped ones, so I finally got a proper 11 piece Wiha T-handle set.  Throwing them in a drawer is like playing Barrel of Monkeys.  Turns out, Wiha doesn't have a rack for them and you can't find one for an 11 piece set on Thingiverse.  My design has optional magnets in the base or snap-in legs that fit in the recesses for the magnets.
 
Now somebody has to explain to me why Wiha has one orientation of the flats on the hex for 10 of the wrenches, and a 30 degree different orientation for the 3/8" wrench. <*fumes*>. Discovered this too late, so there will be a reprint.  Cad file here:  https://cad.onshape....03f52dd8bfca454
 
Making holder for T-handle hex keys

Edited by Dave Cook, Yesterday, 11:15 PM.

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#52 Thomas_M44

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Posted Yesterday, 11:26 PM

 

Today the polishing goodies showed up.  I got sampler packs of the Chemical Guys polishing compounds and their foam polishing pads.  They actually have 7 different levels of firmness on the pads (overkill anybody??) but I figure the 3 pads in the smaller sampler pack should be fine.  The pads have standard hook-and-loop on the back.

 

Man, I hope you're wearing a *really good* respirator that fits well.

 

Metal polishing can be a real mess, and pose a serious inhalation toxicity danger.

 

The polishing compounds can be hazardous themselves, and many older aluminum alloys actually can contain a substantial amount of lead, and/or other toxic metals you *definitely* don't want to breathe frown.gif

 

I'm likely "preaching to the Choir" about the above, but I simply care, and thought it worth saying, if even only for the benefit of others reading the thread.

 

But yes, on another note: your work is looking great Dave waytogo.gif


Edited by Thomas_M44, Yesterday, 11:29 PM.

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#53 Dave Cook

Dave Cook

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Posted Today, 01:03 AM

Actually this stuff is all for polishing the paint, which produces next to no residue compared to the sanding (everything done outdoors btw with my 3M cartridge respirator).  The Chemical Guys auto paint polish is probably too fine to be very effective on metal.  And yeah, the aluminum in Cave's castings is not the modern stuff, no telling what's in it.  I've been pretty careful about not doing anything that would make a lot of fine aluminum dust.  Rocketry folks know that very finely ground aluminum (we're not talking machining chips here) is actually a viable propellant additive, and having a lot of it floating around is an *explosion* hazard.  Powdered aluminum below a certain size is actually a regulated product because of that.

 

Another thing people should know about older telescopes is that lead based paint was not banned until 1978, near the very end of Cave Optical production.  It's a fair guess that the original paint on many older mounts (Cave, Parks, Criterion, etc) would have lead content.  A good reason to prefer the Citristrip, which doesn't throw dust into the air, vs wirebrush or sandblasting.




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