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PST One stripped fastener

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#1 BinoGuy

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Posted 14 May 2019 - 04:43 PM

So we tried opening the PST to verify the prism was perpendicular to both the etalon and eyepiece, but Coronado clearly does not use hardened steel for their screws.  A few very gentle attempts and the hex head is reamed out.  The rest of the screws came out fine but the lid (side) is very firmly still attached.  So now I'm stuck, I could close it up and say it is as good as it is (short of sending a new scope to Coronado for an expensive check up) or I can try drilling.  I expect I can remove the shavings without a problem but I fear it would reduce future options.

 

Thoughts?



#2 jwestervelt

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Posted 14 May 2019 - 05:35 PM

I don't know what the screw looks like that you are trying to work with, but usually drilling is effective because the screw goes through an unthreaded hole in one piece and into a threaded hole in the bottom piece.  Drilling is done to remove the head of the fastener so the top piece is no longer secured, but then you need to put a wrench on the remaining stub of the screw and back it out of the hole.  You don't usually try to drill out the whole screw since that will damage the threads in the piece. 

They do make reverse twist drill bits designed for biting into the screw and backing them out.  But obviously any work you do is at your own risk.  :(


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#3 Eddgie

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Posted 15 May 2019 - 07:17 AM

https://www.amazon.c...=gateway&sr=8-1


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#4 DAVIDG

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Posted 15 May 2019 - 09:14 AM

 They used a glue on the thread of the screws. So try this, first  find a flat blade screw driver that will fit snugly into the stripped out hole. You may need to file one down so it is just the right size and tap it down down into the hole for tight fit.  With the screw driver removed  take a soldering iron and place it against the head of the screw. You need to get it good and hot so it may take 10 minute or so of heating to soften the glue. Then try to unscrew it with the screw driver down in the hole.

 Another approach that has also worked for me is if you have a Dremel tool, you can use a cut off disk that comes with them and cut a slot in the head of screw that again a flat blade screw driver will fit in. Again I would heat the screw and try unscrewing it when hot.  Good luck !

 

               - Dave 


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