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Equipment Discussions >> Mounts

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Mr Greybush
scholastic sledgehammer
*****

Reged: 05/16/13

Loc: Virginia
stripped threads 8" sct
      #6130618 - 10/11/13 09:28 AM

I have a stripped threads in 1 outer OTA hole. What can I do to fix it.

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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: stripped threads 8" sct new [Re: Mr Greybush]
      #6130648 - 10/11/13 09:47 AM

Well, the only question I have is "What does it do that it needs fixing?"

There are several things you can do.

First is to chase it out with a tap. You can buy an inexpensive set of taps at places like Harbor Freigh (complete sets, metric or SAE, but you have to know the standard of course).

If the hole is just cross threaded, this is all you need to do.

Next, you can drill out the hole and tap it for the next larger size.

Third option is to drill it out large enogh for a Helicoil insert but this is usuallly for larger holes and I don't know if there is any hole this big on an SCT.

So, most likley your only option is to tap it out for the next larger size.

If it is something like a finder bracket hold, you may be able to fill it with liquid Metal, re-drill it and retap it.

I don't know if I would trust this for a dovetail screw, but for an accessory screw it would be fine.

If you can get to the inside, the last option is just use a longer screw and pull the corrector off and put a nut on the inside.

Almost all of the repair methods are going to result in metal particals in the OTA and honestly I would pull the mirror to do it because you need to cover the baffle so that metal particals don't get into the grease.

But all of this goes back to my original question.. What screw is it, and do you really need to repair it????

Did you perhaps loosen one of the OTA screws and it won't tighten now? The hole for these are not tapped. They are backed up by a nut. If you loosend one, the nut is loose.

You can leave it alone, or you can pull the corrector to get at the nut so you can hold it while you tighten it.

If you removed the screw, the not is in there Agent Mulder, and you have to go in and get it out.


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Mr Greybush
scholastic sledgehammer
*****

Reged: 05/16/13

Loc: Virginia
Re: stripped threads 8" sct new [Re: Eddgie]
      #6131059 - 10/11/13 12:53 PM

Thanks for the reply I'm having a professional do it. I'm not taking a chance of messing it up and for $75 its worth it.

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WillCarney
Pooh-Bah
*****

Reged: 10/08/09

Loc: Bloomington, ILL
Re: stripped threads 8" sct new [Re: Mr Greybush]
      #6131161 - 10/11/13 01:34 PM

Quote:

Thanks for the reply I'm having a professional do it. I'm not taking a chance of messing it up and for $75 its worth it.


Probably best if you never done it. I had experience so I had no problems drilling two holes in my C-8 SCT and threading them for a second finder bracket. Now I have two mount places for standard finders. William

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Billydee
professor emeritus
*****

Reged: 01/23/08

Loc: Winter Haven, FL
Re: stripped threads 8" sct new [Re: WillCarney]
      #6131463 - 10/11/13 03:59 PM

John L.,

By the time you would get everything together to do it yourself it would have probably cost your $100. You did the right thing to contract it out.

Luck, Bill


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Mr Greybush
scholastic sledgehammer
*****

Reged: 05/16/13

Loc: Virginia
Re: stripped threads 8" sct new [Re: Billydee]
      #6131686 - 10/11/13 06:10 PM

Bill I would loose about $15.00 in gas but the headache and if I did something wrong no amount of loss will make up for it when having someone do it for me. The guy said that he would tap it and replace it with a 5mm screw which sounds right. True?

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Geo.
Carpal Tunnel
*****

Reged: 10/01/08

Loc: Upstate NY
Re: stripped threads 8" sct new [Re: Mr Greybush]
      #6132204 - 10/11/13 11:12 PM Attachment (3 downloads)

Sounds like it's a trunion arm screw, a #10-24. These holes are not drilled radially. 5mm is a closer thread than a #12.

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