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CG5 mountng knob/bolt replacement ?

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#1 BruceGFL

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Posted 30 March 2013 - 07:33 AM

Good Day All, I have an older CG5 mount with the accessory tray nearer the bottom and the Celestron non-computer driven equatorial mount. This morning I discovered the grasping handle of the knob in pieces lying in the tray, shattered from age I guess. Would a new part from Celestron fit and be of the same screw pitch?

http://www.celestron...-four-prong....

Thanks for any and all help

#2 jbalsam

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Posted 30 March 2013 - 09:53 AM

Hey Bruce. Do you have a thread-checker? If so, measure the threads and let me know what they are. I'll measure the threads on my CGE bolts (the one you linked to) and let you know if they are the same.

#3 Geo.

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Posted 30 March 2013 - 06:54 PM

Not sure what you mean by the grasping handle of what. The CG-5 is principally metric. The parts that have plastic hand wheels are the dovetail saddle clamping bolt. That's M8x 1.25. The tripod hub retaining bolt - M10x 1.5 and the Az fine adjustment screws, think these are M5 or M6. The 3/8-16tpi is the bolt that secures a fork mounted scope to the equatorial wedge. The holes in the fork base are 3/8-16.

Try here: http://tinyurl.com/cogz7jn

#4 BruceGFL

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Posted 01 April 2013 - 05:13 PM

JBalsam, apologies but I do not have a thread checker. Thanks for the offer though.

Geo. To be more specific, I meant the grasping knob which fits around the center mounting bolt. This bolt comes up through the center of the tripod and secures the equatorial mount to it. It looks like a tooth gear with 4 projections or teeth for grasping. Apparently the bolt head was press fitted into this plastic knob to make it easier to spin without using a wrench. Sorry if I'm making this more confusing. With what was left in the accessory tray, it must have looked like the one in the Celestron link above. The now revealed bolt head is definitely 9/16th. Hope this helps.
Thanks Everyone !

#5 BruceGFL

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Posted 01 April 2013 - 06:36 PM

I've just realized a photo is worth those 1000 words so here is a the bolt and the center hole it comes up through to secure the equatorial mount to the tripod. Actually now that I have measured it, I was wrong is guessing that part in the above Celestron link is it.
But imagine this bolt with that 4 tooth plastic handle pressed over the bolt head and you have it. Any ideas??
And should this bolt be smooth in the middle as it is. I purchased this mount and tripod second hand so I do not have any manuals.

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#6 BruceGFL

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Posted 01 April 2013 - 06:40 PM

Apologies but I do not know how to add multiple photos so the next two will come separately.

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#7 BruceGFL

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Posted 01 April 2013 - 06:41 PM

One more

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#8 BruceGFL

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Posted 01 April 2013 - 06:44 PM

And

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#9 Skrenlin

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Posted 01 April 2013 - 06:47 PM

That's the bolt (that used to have a hand-nut on it) that screws the mount down onto the tripod? I'd take it to your hardware store. There are plastic finger knobs made now that are press fit on to most bolt sizes.

#10 skywolf856

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Posted 01 April 2013 - 07:07 PM

That looks like a home made captive screw.
The threads are filed down in the center to allow screwing thru a tapped hole then attaching to another thread above that while the body of the filed down screw passed through the first threaded hole without binding.

#11 BruceGFL

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Posted 01 April 2013 - 07:43 PM

Hi Skrenlin, you are correct. That is the bolt which had the four tab spinning plastic knob pressed on to the top. Which is now shattered, a problem I have not idea how it happened.

Skywolf, yes, where it passed through the tripod top plate is threaded along with that silvery part on the equatorial mount. So you think it should be smooth in the middle for snugging up?

#12 Agatha

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Posted 01 April 2013 - 08:36 PM

Bruce,

I agree with Skywolf 856, it looks like a homemade bolt for the purpose. That's just fine. Yes, it is normal for the middle part to be smooth. It allows you to push it up to the mount base and then start threading/tightening it. I'm assuming that there is a washer or spacer of some sort for the bolt near the head end.

Best, Linda B.

#13 BruceGFL

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Posted 02 April 2013 - 03:26 AM

Linda,
Yes there is a washer at the bolt hear, I appreciate your input.


Best Regards, Bruce

#14 BruceGFL

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Posted 02 April 2013 - 03:27 AM

Linda,
Yes there is a washer at the bolt head, I appreciate your input.


Best Regards, Bruce

#15 Geo.

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Posted 02 April 2013 - 06:07 PM

That's not homemade that's China made! They take a standard 10-1.5 metric bolt and machine off some threads. Generally when this happens to me I find a short piece of 1/4" steel rod and braise it to the top of the bolt to replace the plastic. Overtime plastic looses its plasticizers, get brittle and fails. Off gassing plasticizers are give you that "new car smell."

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