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CGEM II stripped azimuth adjustment knob threads

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12 replies to this topic

#1 Vinnyvette01

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Posted 19 July 2019 - 12:50 AM

Synopsis:
Looks like my CGEM II azimuth adjustment knob threads are beginning to strip from inside the mount's housing. There is lots of play from both azimuth adjustment knobs. It's only a matter of time when they will no longer thread properly.

Question:
The azimuth knobs are 8mm threads. I'm contemplating retapping the mount housing azimuth adjustment threads to 10mm and adding the 10mm ADM altitude adjustment T knobs in place of the standard 8mm azimuth knobs. Is there a better solution? **I do not want to use a helicoil kit.** I want to fix it right the first time. Also, what size are the azimuth adjustment knobs on the CGX-L? Maybe I can use those if they are 9mm or bigger.

Any input is much appreciated!

Edited by Vinnyvette01, 19 July 2019 - 12:53 AM.


#2 macdonjh

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Posted 19 July 2019 - 07:54 AM

If you don't want to use a helicoil, perhaps your only other option to drilling and retapping is to use something like JB Weld, then redrill for 8mm and retap.  Why don't you want to use a helicoil if you're considering drilling and tapping for 10mm?  The helicoil has to be more durable than the aluminum casting of your mount's housing.



#3 mich_al

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Posted 19 July 2019 - 11:25 AM

Search 'thread restorer loctite' : it's a product I've used with great results on similar applications, probably available from other manufacturers too.  It is an epoxy product that you coat the threaded portion with, after applying a release agent, and insert in the damaged threaded hole.  After a short time (monitor VERY close) the you separate the two part and allow to further cure.  Easier than some others yet still allows them if you don't like the results (but you probably will).



#4 elinchrom

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Posted 19 July 2019 - 03:23 PM

This is how I fix my CGEM:

https://www.cloudyni...zona/?p=8316668

basically, I just use a larger bolt center drill and tap with 8mm thread.



#5 Vinnyvette01

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Posted 20 July 2019 - 07:54 AM

If you don't want to use a helicoil, perhaps your only other option to drilling and retapping is to use something like JB Weld, then redrill for 8mm and retap. Why don't you want to use a helicoil if you're considering drilling and tapping for 10mm? The helicoil has to be more durable than the aluminum casting of your mount's housing.



#6 Vinnyvette01

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Posted 20 July 2019 - 08:05 AM

I figure since the azimuth adjustment knobs will be loosened and tightened everytime I polar align and the helicoil can't bottom out into the mount, the helicoil could potentially back out. Maybe JB weld will hold it in place permanently. I could test it on a spare piece of aluminum first.

#7 Vinnyvette01

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Posted 20 July 2019 - 08:08 AM

This is how I fix my CGEM:

https://www.cloudyni...zona/?p=8316668

basically, I just use a larger bolt center drill and tap with 8mm thread.



#8 Vinnyvette01

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Posted 20 July 2019 - 08:12 AM

I like the idea of having a steel insert in there. That's what Celestron should have done in the first place!
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#9 Vinnyvette01

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Posted 20 July 2019 - 08:14 AM

If you don't want to use a helicoil, perhaps your only other option to drilling and retapping is to use something like JB Weld, then redrill for 8mm and retap. Why don't you want to use a helicoil if you're considering drilling and tapping for 10mm? The helicoil has to be more durable than the aluminum casting of your mount's housing.



#10 Vinnyvette01

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Posted 20 July 2019 - 08:15 AM

I think redrilling and retapping with epoxy is just a bandaid though. That epoxy will chip out over time.

#11 mclewis1

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Posted 20 July 2019 - 08:32 AM

If you don't want a heli coil consider using an EZ Thread or E-Z loc threaded insert.  A properly installed heli coil should not ever come out but these other options are a bit more robust and are usually installed with a thread locking compound to further prevent any backing out.

 

A threaded insert is the right way to fix the altitude or azimuth bolt issues (it fixes the damaged threads and provides a much better quality thread for the continued use of the bolt when it's under load).


Edited by mclewis1, 20 July 2019 - 08:34 AM.


#12 Vinnyvette01

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Posted 20 July 2019 - 01:56 PM

If you don't want a heli coil consider using an EZ Thread or E-Z loc threaded insert. A properly installed heli coil should not ever come out but these other options are a bit more robust and are usually installed with a thread locking compound to further prevent any backing out.

A threaded insert is the right way to fix the altitude or azimuth bolt issues (it fixes the damaged threads and provides a much better quality thread for the continued use of the bolt when it's under load).



#13 Vinnyvette01

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Posted 20 July 2019 - 02:11 PM

I like this idea. Those E-Z Loc inserts can be purchased as a full kit (E-Z LOK EZ-450-8) and are available in size M8-1.25 ID x M12-1.75 OD. They are made from carbon steel, are specifically for use in metal, and are a half inch in length. I will need to measure how deep the mount's azimuth holes are. I'm hoping they are more than a half inch deep so I can countersink to a half inch for the inserts. That will allow the inserts to bottom out and mate against the existing stripped 8mm hole. I will use red Locktight to ensure the inserts will not back out.

Thanks for the info, mclewis1 and "clear skys"!

Edited by Vinnyvette01, 20 July 2019 - 03:13 PM.



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