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Eyepiece Set screw ETX90


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#1 RickScofield

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Posted 05 October 2014 - 04:51 PM

Hello all,
I am look for some advice,the threads for the set screw for holding the eye piece in place are striping out on my ETX 90. Does anyone have any idea how I can restore these threads? These threads are in plastic.

#2 MistrBadgr

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Posted 05 October 2014 - 06:04 PM

Hi Rick,

 

Hopefully, that is on your diagonal and not on the scope itself.  I don't think you can rejuvinate the threads in that size, but you might try the next size up.  When the threads finally strip out, take your thumb screw to the hardware store and verify its size.  I think it is 4 mm, but you probably need to check.  Get a 5mm screw and see if you can work it into the hole and cut a new set of threads with it.  My experience has been with loosing the screws, rather than cutting out the threads, but I can see that happening.

 

If they don't have a real thumb screw, which I have not found yet at my hardware store, at least not in stock, I have replaced missing screws using SS cheese head screws, which have a thicker head than a regular one.  I cut notches in the circumference of the head with a triangular file to give it some grip.  I also file the end smooth, where it will touch the eyepiece barrel to keep from scarring that.

 

The other option is to buy a new diagonal.  The Meade # 983A prism diagonals work pretty good.  I am assuming that the ETX 90 has a regular 1.25 inch back on it and not a back that is already the diagonal.

 

I would be interested in hearing of someone else has a better option.  You never know when you will need that kind of information.

 

Hope this helps,

 

Bill Steen


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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 RickScofield

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Posted 06 October 2014 - 04:23 AM

Bill,

Thank you for your response. I wish this was on the diagonal however this is the set screw on the telescope. It’s to the point now that it has hardly any retention resistance. I guess the day to day use of swapping eyepieces has proven to be too much for plastic threads. I have measured this screw at 9/64 or 3.57mm.      



#4 RickScofield

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Posted 06 October 2014 - 06:45 PM

Bill,
I made a trip to my favorite hardware store and found a good stainless screw with the same threads but rather than 3.57 MM , 9/64 this screw is 3.97 MM , 5/32. This worked out just great. I had to work with it at first but after a little effort and an extremly small amount of machine oil, I was lucky enought to get it to work out and more or less tap its own threads. I think this will take care of my problem but then only time will tell if that's true. Thank you for your advice it was right on.

#5 MistrBadgr

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Posted 06 October 2014 - 06:51 PM

Rick,

 

I also downloaded and looked at pictures of the ETX 90, and it definitely has a different layout than anything else I have run into....not bad, just different.  One thing I did read was the instructions for inserting an eyepiece.  It says to tighten the screw until firm only.  I guess that means just touching the eyepiece barrel to keep it from moving around, but not truthfully tight.  There is a thing with the plastic threads, apparently, which you have discovered.

 

Glad to hear you found a screw that will work.  Bigger threads mean more surface area to spread the forces around on.  I expect it will work better for you.

 

Bill


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#6 RickScofield

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Posted 06 October 2014 - 06:56 PM

image.jpg

#7 RickScofield

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Posted 06 October 2014 - 07:01 PM

Bill ,
A sincer Thank you for your time and great advice. I added the photo above for the record. I also want to thank Meade for this WEB SITE. What a great resource.

#8 MistrBadgr

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Posted 06 October 2014 - 07:48 PM

Thanks, Rick!  Glad to be of help and happy that you got yourself fixed up.

 

(Scopes work better when you fix up things like that anyway.  It puts a little of YOU in the scope!)

 

Bill


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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#9 Mark Sibole

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Posted 07 October 2014 - 05:32 AM

Im surprised the EP holder is plastic on the ETX.There must have been a design change over the years on it.It used to be aluminum.They must have implemented some cost cutting designs.Just use slight pressure on the EP so you dont strip it out again.In many cases you can just re tap the hole and replace the screw like you did.Glad your back in business.

 

Regards

 

Mark


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Mark Sibole
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#10 RickScofield

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Posted 07 October 2014 - 07:09 AM

Mark,

Thank you and I had issues with the threads on this from day one. When you look these over on-line they don't tell you what they are made of. I am sure its all about cost and margins but this is something that I would think should not be plastic. It's a failure point for sure. I'll be sure to be very careful with this and hope it doesn't happen again.     

 

Rick Scofield   



#11 Mark Sibole

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Posted 08 October 2014 - 06:12 AM

well if you have any further issues let me know.There isnt to much i cant fix to save money.

Im always around and always willing to help out someone in need.I dont know how many screws and things ive given away from my personal stock free of charge to help others out.Eventually I may have to call John and have him send me some misc stuff to keep on hand for people who need parts.


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Mark Sibole
MTSO Observatory
Fife Lake, Mi.

http://astronomy.qteaser.com

#12 RickScofield

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Posted 08 October 2014 - 08:13 AM

Mark,
Thank you, but I should'nt need anything else. I'm going to post a final picture, I modified my replacement screw.image.jpg

#13 MistrBadgr

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Posted 08 October 2014 - 12:33 PM

Now that is a real thumb screw!

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma




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