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Thread repair

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#1 dusty99

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Posted 23 June 2020 - 03:29 PM

Hi everyone.  I recently picked up a Scope Orbit (the one I posted in the classic scope picture thread) and the aluminum hand screw end that keeps the EQ mount together is stripped.  The steel bolt itself seems fine.  Would cleaning the inside well and applying a thin coat of JB Weld then recutting the threads work?  Does anyone have other ideas?  There's not a lot of weight on this part, but it must be tensioned...

 

I have a couple of other questions about the Scope scope, but since this must be a pretty common problem faced with older mounts, I thought I'd ask it separately.  Thanks!

 

IMG 2201

 

 

ScopeOrbit60 800

 


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#2 Sean Cunneen

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Posted 23 June 2020 - 03:43 PM

Can you post a pic of the affected parts? What is your top pic of?Do you know the size of the thread/tap you would need? I would nix the jbweld idea. There wouldn't be enough surface to adhere to and I would think the jbweld would grind itself out in a very short time. I would want more info to be sure, but stepping up the bolt size or drilling and tapping a set screw might be an alternative.


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#3 Elaine Stachowiak

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Posted 23 June 2020 - 04:06 PM

thread repair kits:many sizes available. i have never tried the loctite product. I use to work in a machine shop and have used the insert types for good permanent fixes. maybe see if someone you know has some of these or ask around some machine shops.

hope this helps.

 

https://www.amazon.c...2944730&sr=8-17

 

https://www.amazon.c...rkle_mcd_asin_2

 

https://www.mcmaster...tallation-tool/

 

https://www.amazon.c...rkle_mcd_asin_2

 


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#4 apfever

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Posted 23 June 2020 - 06:25 PM

That part looks like a counterweight shaft tensioner.

The JB Weld isn't a bad idea for grins. JB could be touchy but you might try a short bolt of the right thread. Wrap the bolt with Teflon tape. JB your part. Place the part upright and thread the bolt in. Make sure you wrap the bolt the right direction with the T tape and have some shop sense about it all.  Run the bolt down till it bottoms on the table and sits 'neutral' on it's own weight, it's a 'feel' it sort of thing.  Consider a nylon bolt and T tape. The result might work fine as is or it should be a very easy tap to clean up. Make sure that part is CLEAN for the JB.  A greasy bolt wouldn't bother me too much. This would be big time better than tapping JB from scratch. 

 

It is up to you to consider the bolt getting JB welded to the part. 

 

The Heli coils would work but may not be as long as the original threads. I'm not a fan of them even for cars which is what Heli coils are primarily used for.  This one is a poorly done VW bus D port head spark plug hole.  I'm removing the Heli and going back to scratch with a weld fill in.  It's a full domed block 2000cc, factory internally clearanced, vanagon D head, original bus edition, builders prime choice to handle insane horse power.....oops sorry mods.  Not for sale Tim.

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Edited by apfever, 23 June 2020 - 06:45 PM.

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#5 Russell Smith

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Posted 23 June 2020 - 06:36 PM

If your not obsessed with original, stepping up in size could do the job.
Personally, I like apfever's idea.

#6 clamchip

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Posted 23 June 2020 - 06:46 PM

A Helicoil or Threaded Insert would be a good repair, but these two options may

be more expensive than the part itself.

You might take the screw to a hardware store and buy a regular nut to replace

your stripped nut. I recommend Ace Hardware if you have one close. 

You could try wrapping the right size copper wire on the male and see if you can

restore a tight fit. You would need to use just the right size.

I've seen fishing line used for this purpose on small fasteners.

 

Robert 


Edited by clamchip, 23 June 2020 - 06:48 PM.

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#7 DAVIDG

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Posted 24 June 2020 - 08:57 AM

 Another possibility is the low melting Aluminium alloy welding sticks that you can heat with a common propane torch. You put the shaft back in the threaded hole, heat the part and melt in the alloy. Let it cool and it reforms the threads.  There are a number of on line video of how it is done. You can get the welding sticks at Harbor Freight or order them online.  Here is  a video on how to repair the threads https://www.aluminum...actual-repairs/

 

               - Dave 


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#8 dusty99

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Posted 24 June 2020 - 10:00 AM

Thanks, everyone.  I have access to a MIG welder but didn’t want to have to refinish the piece, which holds the cradle together on one side and then takes the counterweight rod on the other (which is why a nut won’t do).  This setup means that every time you assemble and disassemble the scope it needs to be threaded/unthreaded, and due to the counterweight’s mass (maybe 5 lbs) it’s under some pressure.  On closer inspection there is a bit of thread damage to the rod threads, too. This is a bit of a design flaw but the goal must have been to keep the box small and tidily arranged, so the rod and weight needed to break down.  With summer getting busy again I may just post it for sale and see if someone with the time wants to do a real restoration, or I could wait until I have time to properly fix the threads.  I suppose I could add some metal inside the locking piece and tap two different threads on each side, then cut next-size down threads on the counterweight rod.  
 

I’m a little bit puzzled that the mount has such a heavy counterweight in the first place.  It’s a lightweight 60mm with an 800mm focal length, and works just fine on my little Unitron altaz.  Maybe the same Mount was used for longer scopes, but this one would be fine with a counterweight half that size.

 

Dave: thanks for pointing me to the HTS2000.  I had no idea something like that was out there!


Edited by dusty99, 24 June 2020 - 10:02 AM.


#9 RichA

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Posted 24 June 2020 - 06:22 PM

Hi everyone.  I recently picked up a Scope Orbit (the one I posted in the classic scope picture thread) and the aluminum hand screw end that keeps the EQ mount together is stripped.  The steel bolt itself seems fine.  Would cleaning the inside well and applying a thin coat of JB Weld then recutting the threads work?  Does anyone have other ideas?  There's not a lot of weight on this part, but it must be tensioned...

 

I have a couple of other questions about the Scope scope, but since this must be a pretty common problem faced with older mounts, I thought I'd ask it separately.  Thanks!

 

 

 

 

Your idea is a good one, tough to do right.  But I've done it.



#10 rigelsys

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Posted 24 June 2020 - 06:39 PM

I'd suggest drilling the hole out to a larger size for a spacer, then drill and tap a hole in from the side for a set screw.  Press the spacer with the right threads (if you can't find a threaded one, get a smooth one and tap it yourself) into the larger hole.  Now run the tap drill in from the side to dimple inthe spacer for the set screw tip to index into and run the set screw in to lock the spacer in place.

 

simple and affordable :-) 



#11 dusty99

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Posted 24 June 2020 - 09:22 PM

That’s a good thought, and it already has a set screw on the cradle side.

#12 Senex Bibax

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Posted 25 June 2020 - 07:46 AM

I've successfully used helicoil inserts to repair threads in aluminum alloy, motorcycle crankcases for example


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#13 badback

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Posted 01 July 2020 - 05:36 PM

I've been a mechanic most of my life. gramps.gif

I've seen this problem on EQ mounts numerous times.

 

Other than someone cross threading this aluminum piece, which

would not be easy to do (due to coarse threads) that "set screw"

is likely the cause of your stripped thread grief. I strongly suspect

that in this scope's history (perhaps when it was first assembled)

this set screw was tightened a bit too much and it buggered up

the steel shaft threads. If the set screw was overly tightened

(or even semi-tight) it could have become mushroomed. That

would have made it difficult to unscrew far enough to prevent further

thread problems to the steel shaft while attempting to remove the

aluminum piece.

 

So... when the aluminum piece was eventually unscrewed, the still

in place tight set screw, would further damaged the steel shaft.

Then, when the aluminum piece was re-installed, it's threads were

likely damaged even more due to the steel shaft's now damaged

threads. Eventually the aluminum piece became fully stripped.

gaah.gif

 

Been there, done that. Seen it. Fixed it many times.

 

 THE FIX idea.gif :

1: Heli-Coil the stripped aluminum piece.

2. Make sure the set screw doesn't interfere with the Heli-Coil threads.

    Either unscrew the set screw out far enough, or ground it down so

    that it doesn't  cause future problems.

3: If the steel shaft is too "screwed up" lol.gif you might consider buying

    a  thread file. I've used em' for years. The can, and have been,

    invaluable parts savers for me on many occasions. Very very useful:

 

thread files.jpg

 

    Finally: "Screw the steel set screw." ranting.gif

    Now use Locktite to hold the aluminum piece in place after adjustment.

    Works like a charm and no more stripped threads.  waytogo.gif

 


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#14 dusty99

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Posted 01 July 2020 - 05:48 PM

Sounds like a couple of helicoils will be where I start.  Thanks, all!



#15 mich_al

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Posted 01 July 2020 - 11:26 PM

I've used the Locktite thread repair stuff with great results.

https://www.amazon.c...=osi&th=1&psc=1


Edited by mich_al, 01 July 2020 - 11:29 PM.



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