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Secondary mirror collimation hex screws rounded

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#1 Kitchy65

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Posted 21 May 2019 - 12:21 PM

Own a used 150mm skywatcher dob.

 

On attempting collimation i've noticed all 3 adjusting screws are rounded off...as they are recessed I have no idea how to remove them to replace.

 

Any advice would be great..



#2 clusterbuster

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Posted 21 May 2019 - 12:48 PM

maybe a pair of small vice grips could do it.

 Mark



#3 earlyriser

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Posted 21 May 2019 - 12:52 PM

You could epoxy an allen head wrench into the hole and remove the screw after the epoxy cures. Use a small enough amount to avoid bonding the screw/wrench to the sides of the recess.



#4 csrlice12

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Posted 21 May 2019 - 12:55 PM

Start here...

https://www.google.c...ce=browser-type


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#5 SteveG

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Posted 21 May 2019 - 01:02 PM

Remove the spider assembly from the tube. Loosen the large center screw. Now the 3 smaller screws should be loose. You can try to thread them out from behind using your fingers, until you get enough of the Allen head exposed.

 

Or purchase the tools linked above.


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#6 trapdoor2

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Posted 21 May 2019 - 01:16 PM

Before you tear it all apart, go to Bob's Knobs and purchase a set of collimation knobs for your scope.

 

http://bobsknobs.com...ge66/SWdob.html

 

Once you have the originals out (I'd use SteveG s method above), replace them with the Bob's Knobs. Done!


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#7 earlyriser

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Posted 21 May 2019 - 01:26 PM

Remove the spider assembly from the tube. Loosen the large center screw. Now the 3 smaller screws should be loose. You can try to thread them out from behind using your fingers, until you get enough of the Allen head exposed.

 

Or purchase the tools linked above.

We have a winner. You could probably even do this without removing the spider assembly.


Edited by earlyriser, 21 May 2019 - 01:36 PM.

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#8 Kitchy65

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Posted 21 May 2019 - 04:16 PM

Thanks for the advice



#9 pyrasanth

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Posted 21 May 2019 - 04:44 PM

This thread reminds me as to how poor the quality of some steel has become. Unless your tools fit exactly it is really easy for a metric tool to have a very poor fit in an imperial socket or vice versa- the heads will round especially with Allen heads. I feel we just need to be careful and use the right tools.


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#10 David Castillo

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Posted 21 May 2019 - 05:46 PM

Or, if you're frugal, like me, buy (3) M4-.7X40mm Hex bolts, and (3) wing nuts that fit. ( Home Despot has them).Take the wing nuts almost to the bolt end, put a small dab of CA glue on the last few threads at the head of the bolt,and snug the wing nuts up (and leave them set for a while). Now you have a collimation bolt with an wing nut to finger adjust your secondary. Mine have served me well for more than 10years. I had to shell out around $6 total -I'm Sorry Bob, but no sale for you!


Edited by David Castillo, 21 May 2019 - 05:54 PM.


#11 mjulihn

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Posted 21 May 2019 - 07:01 PM

Remove the spider assembly from the tube. Loosen the large center screw. Now the 3 smaller screws should be loose. You can try to thread them out from behind using your fingers, until you get enough of the Allen head exposed.

 

Or purchase the tools linked above.

Yep, this should do it!




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