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Celestron CG-4 Screw (bolt?) sizes

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#1 rolleikin

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Posted 22 August 2019 - 10:46 AM

Hello,

 

I have a CG4 mount and I need to replace the two screws (or are they called bolts?), but they do not have any markings as to their size, and there is no information in the manual. I am going to venture a guess that they are all metric, but what do I know?

 

The first bolt has a large plastic knob and it is the main way to tighten the Vixen dovetail. 

 

The second bolt is much smaller and has a metal thumbscrew end. I am not sure what is its main purpose other than hold the Vixen dovetail even tighter. 

 

If somebody could tell me what thread size they are and how long they need to be. I don't have any fancy tools to measure threads and such. 

 

I am attaching a picture. 

Attached Thumbnails

  • CG4 screws circled small.jpg.jpg


#2 vtornado

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Posted 22 August 2019 - 11:09 AM

I don't know either, but usually when I need to buy replacement bolts for anything,

I take the whole mount head into my friendly ACE store.  They don't mind me

rummaging through the fastener drawers.   I have replaced parts on these mounts,,

and most if  not all the bolts are metric. 

 

If you have a drill, and a small saw, you can make a circular hole in a small square of wood,

an glue this onto a hex cap bolt that you will use to replace the missing knobs.  Some home

depots have a box of defect lumber, that is almost being given away, and comes in small pieces.

Used cutting boards at good-will are also excellent scrap material.

Making this knob  will give you something to grip onto to hand tighten the bolt.



#3 Eye stein

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Posted 22 August 2019 - 11:29 AM

If you can remove them easily, take them to Lowe 's or Home depot store..hardware isle. they usually have a  board set up

with tapped holes etc. for you to try your bolt (they have both metric and standard sizes too!)

many threads are different to ,so you should at least find out the size  and length you need.

They sell various sizes too.

I always try them first. good luck and clear skies



#4 rolleikin

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Posted 22 August 2019 - 12:30 PM

If you can remove them easily, take them to Lowe 's or Home depot store..hardware isle. they usually have a  board set up

with tapped holes etc. for you to try your bolt (they have both metric and standard sizes too!)

many threads are different to ,so you should at least find out the size  and length you need.

They sell various sizes too.

I always try them first. good luck and clear skies

I cannot remove the bolts/screws. I lost them already. 



#5 rolleikin

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Posted 22 August 2019 - 12:32 PM

I don't know either, but usually when I need to buy replacement bolts for anything,

I take the whole mount head into my friendly ACE store.  They don't mind me

rummaging through the fastener drawers.   I have replaced parts on these mounts,,

and most if  not all the bolts are metric. 

 

If you have a drill, and a small saw, you can make a circular hole in a small square of wood,

an glue this onto a hex cap bolt that you will use to replace the missing knobs.  Some home

depots have a box of defect lumber, that is almost being given away, and comes in small pieces.

Used cutting boards at good-will are also excellent scrap material.

Making this knob  will give you something to grip onto to hand tighten the bolt.

I cannot take the bolts to Home Depot because I already lost them. Can't measure them anymore :(



#6 SkipW

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Posted 22 August 2019 - 02:16 PM

Bring the mount head to the store and find machine screws that fit. They're virtually certain to be metric.

 

If you can't or don't want to take it to a hardware store, you can get a plastic card for sizing screws, bolts, nuts, and small pipe for a couple of bucks.

 

These parts on the CG-5 are M8 X 35 mm and M4 X 25 mm - those lengths are the length of the threaded part. I'd bet they're the same on a CG-4, so that's where I'd recommend you start looking.

 

Once you confirm the size, you should be able to find knobs and thumbscrews online if not available locally (local would be unlikely). For instance...

 

https://www.amazon.c...WXTH576T06&th=1

 

[Edit to add] Oh, yes... the smaller screw is a safety. It's to keep the dovetail from slipping out if the main clamping screw gets loose.

 

Good luck, and please let us know what you find!


Edited by SkipW, 22 August 2019 - 02:22 PM.


#7 rolleikin

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Posted 22 August 2019 - 02:33 PM

Bring the mount head to the store and find machine screws that fit. They're virtually certain to be metric.

 

If you can't or don't want to take it to a hardware store, you can get a plastic card for sizing screws, bolts, nuts, and small pipe for a couple of bucks.

 

These parts on the CG-5 are M8 X 35 mm and M4 X 25 mm - those lengths are the length of the threaded part. I'd bet they're the same on a CG-4, so that's where I'd recommend you start looking.

 

Once you confirm the size, you should be able to find knobs and thumbscrews online if not available locally (local would be unlikely). For instance...

 

https://www.amazon.c...WXTH576T06&th=1

 

[Edit to add] Oh, yes... the smaller screw is a safety. It's to keep the dovetail from slipping out if the main clamping screw gets loose.

 

Good luck, and please let us know what you find!

Thank you. As soon as I get home I start digging. Just using your data as a starting point, I found both hand knobs at Amazon for about 11 bucks together, but I will try to do some measuring at Home Depot, first. They all look weird at me when I show up with various tripods and telescope parts, but I am used to it, by now. 



#8 SkipW

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Posted 22 August 2019 - 03:35 PM

They all look weird at me when I show up with various tripods and telescope parts, but I am used to it, by now. 

Me, too! I don't particularly care, though; it only makes sense to do that and sometimes it means a sale for them. I doubt you're going to be accused of shoplifting an equatorial mount when you leave the store with it!

 

My local HD has some drawers labeled "hard-to-find-parts" with some knobs and thumbscrews in there, near the drawers full of things like stainless-steel socket-head cap screws. The chances of finding a knob or thumbscrew of the specific metric size and length you're looking for in there are slim, but it doesn't hurt to look.



#9 mdbradshaw

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Posted 22 August 2019 - 04:32 PM

I can give you a concrete answer once I get home tonight.  Both thread and length.  I can probably find you a much cheaper source for replacements as well.


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#10 mdbradshaw

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Posted 22 August 2019 - 09:42 PM

SkipW was correct.

 

The larger bolt is M8x1.25 thread (standard metric 8 mm) by 35mm long, knurled knob style bolt.  If you search the web for "M8 35mm knob" you'll find hundreds of versions, pick your favorite.  Cheapest i found on Amazon was a 2 pack for $5.20, but you can go with 40mm long and find a single for $3.50.

https://www.amazon.c...d/dp/B07R4723RP

https://www.amazon.c...d/dp/B0094DF4G4

 

The smaller bolt is M4x0.7 thread (again, standard metric 4 mm thread) by 25mm long thumb screw style bolt.

2 for $4...

https://www.amazon.c...d/dp/B01N3QTMTZ

 

You might find them cheaper at something like McMaster Carr or Fastenal, and you can find them cheaper if you don't need the hand knobs (use normal screws instead).


Edited by mdbradshaw, 22 August 2019 - 09:45 PM.


#11 rolleikin

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Posted 23 August 2019 - 09:35 AM

SkipW was correct.

 

The larger bolt is M8x1.25 thread (standard metric 8 mm) by 35mm long, knurled knob style bolt.  If you search the web for "M8 35mm knob" you'll find hundreds of versions, pick your favorite.  Cheapest i found on Amazon was a 2 pack for $5.20, but you can go with 40mm long and find a single for $3.50.

https://www.amazon.c...d/dp/B07R4723RP

https://www.amazon.c...d/dp/B0094DF4G4

 

The smaller bolt is M4x0.7 thread (again, standard metric 4 mm thread) by 25mm long thumb screw style bolt.

2 for $4...

https://www.amazon.c...d/dp/B01N3QTMTZ

 

You might find them cheaper at something like McMaster Carr or Fastenal, and you can find them cheaper if you don't need the hand knobs (use normal screws instead).

Fantastic, Skip.

 

Thank you. I already placed an order with Amazon and I should have them in my hands by Sunday. Hopefully this thread will be archived so others may benefit from your research.

 

Thanks again. 




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