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How to remove 15.5" glass porthole from it's brass frame. Without breaking it :0)

hawkerdon

By hawkerdon
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hawkerdon

hawkerdon

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I'm an old guy, 79 this year. Years ago built a 6" newtonian from a kit and now am in my second childhood and working on an 8". I also purchased a ship's porthole, frame and all, it must weigh 50#. There is corrosion between the glass and the brass and the screws that hold the lockring in place over the glass are frozen. Presently I am soaking them in WD 40. I've thought about heating the brass which should expand the frame. Would like to get the screws loose first.

If anyone that has already tackled this job has anything I am open for suggestions.

Thanks,

Hawkerdon

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Mr Q

Mr Q

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Hello Hawkerdon and welcome to the SGL.

Because WD-40 is primarily a lubricant, it would be better to use a "rust/corrosion" disolver specifically designed to do this. These products have a penetrating oil vehicle that eats into the rust/corrosion, then disolving it. Because the penitrating vehicle evaporates fairly quickly, several applications may be needed to free the screws. Using heat as you mentioned can be risky in that it may rapidly heat the glass and crack it. When you use the above product, apply a new dose every hour or so and lightly tap the area with a hard object to set up a vibration that helps the penitrating vehicle to work deeper and faster.

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glowjet

glowjet

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Hi Hawkerdon and welcome to SGL, that is 79 years young by the way and and three years my senior, nice to have some company in our age bracket, try " Plusgas " to see if it will loosen those screws, it has been on the go for years, probably get it from Halfords or a garage accessories shop, failing that you will have to drill them out and re-tap the holes and fit new brass screws, although I would prefer to use stainless types :)

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Merlin66

Merlin66

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Welcome on board!

I assume you just want the glass, and not the frame?

Just drill the screws out and then gently saw/ grinding wheel the rim to allow the brass to separate...

back in the 70's the only glass we could get in South Africa for amateurs was porthole glass... we used to trepan various blanks 6" to 10" for the local ATM'ers.

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Charon

Charon

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Hi and welcome to the forum. 'Problem' is with WD 40 is that it evaporates and leaves a residue, during my time at sea we tended to use a spray called 'Phospro' which worked better, whether this spray is still available is another question.

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hawkerdon

hawkerdon

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THANKS for the Hearty welcome. Appreciate the helpful suggestions. Most of the screws are out, though very grudgingly. For future refference: Soaking the screws a couple days in WD40 then tapping them lightly with a hammer and steel rod (one end ground to fit the screw slot) plus a big screwdriver and a strong hand and wrist has worked. Getting the glass out will be another challenge.

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