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Hole drilled too large in dob tube... What is my best option to proceed?

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19 replies to this topic

#1 Starman81

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Posted 10 August 2020 - 04:02 PM

I was drilling a hole to install a navigation knob on my STS 11. The knob has an M12 bolt. My set of drill bits is imperial (non-metric). 3/8" wasn't large enough but close. I didn't have a round file big enough to enlarge the hole gradually and lost patience and used the 1/2" drill bit and made a mess. M12 bolt is 35mm and about 5mm longer than I needed it to be (couldn't find 30mm one) - should probably just use a nut and the whole thing is not very secure due to the too large hole and bolt that's a little too long. 

 

What is my best option to proceed? Some things to keep in mind:

 

- Inside of tube is flocked

- Navigation knob position selected was the optimal position for me--would like to re-use the hole position if at all possible

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#2 Pinbout

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Posted 10 August 2020 - 04:06 PM

washers, spacers... its a knob... lol.gif


Edited by Pinbout, 10 August 2020 - 04:06 PM.

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#3 Stevegeo

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Posted 10 August 2020 - 04:20 PM

Find a nice STAINLESS STEEL  washer  for looks outside  , a rubber washer inside .. for some give 

 

After all, it's just a KNOB.. 

Stevegeo.  


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#4 SonnyE

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Posted 10 August 2020 - 04:21 PM

"- Inside of tube is flocked"

 

No, both sides are flocked. Because the hole goes all da way through.

 

Like Pinbout sez, washers. I would get fender washers, and paint them flat black.

Or, if you can find them, Black Nylon washers.

It is, after all, just a knob. Nobody is going to know but you, and around 100,000 cloudy niter's.

 

I don't think it will show up on a Car Fax Report.

 

Maybe you should get help with the next hole?



#5 JohnBear

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Posted 10 August 2020 - 04:44 PM

Options:

1. Buy new OTA tube - if you really want it to look like new.

2. A knob with a bigger bolt

2. A couple washers, and maybe some JB Weld.

3. A nut pop rivet (not sure if they have metric; but maybe a new knob with SAE bolt)



#6 Starman81

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Posted 10 August 2020 - 05:04 PM

Thanks guys... I knew I was gonna get some flack! 😂

21 holes drilled in either the tube, cradle or rocker and only 2 bungled up. For me, that's good.
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#7 stargazer193857

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Posted 10 August 2020 - 05:06 PM

Bending washers to the curve would be ideal, but I have no idea how. I was thinking a square sheet before I knew which hole you were referring to. Washers sounds easiest and most predictable. They might bend the tube a bit. JB weld could fill some curvature on both sides.

#8 John Fitzgerald

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Posted 10 August 2020 - 05:09 PM

Get nylon washers and dye them black by boiling in a bit of Rit dye.  They will easily bend to fit the tube.



#9 MitchAlsup

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Posted 10 August 2020 - 07:25 PM

I agree with the washer solves the problem.

I also agree that a rubber washer would work better than a shiny washer inside.



#10 Tak North

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Posted 10 August 2020 - 07:51 PM

Lots of rivets and sheet metal patches - now's the time to consider steampunk.

 

I7toPx.jpg


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#11 N3p

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Posted 10 August 2020 - 08:10 PM

Lots of rivets and sheet metal patches - now's the time to consider steampunk.

 

I7toPx.jpg

 

 

Thanks for publishing that image Tak North, it's giving me new ideas.


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#12 JohnBear

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Posted 10 August 2020 - 08:26 PM

Yeah! Steampunk telescopes are the Best!


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#13 kfiscus

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Posted 10 August 2020 - 09:29 PM

Black neoprene washer.



#14 dave brock

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Posted 10 August 2020 - 11:59 PM

Or if you don't want to buy washers, cut 1/4" off the bolt.



#15 JohnBear

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Posted 11 August 2020 - 12:54 AM

 

Or if you don't want to buy washers, cut 1/4" off the bolt

Its a Metric bolt - so that'll be 6.35mm off. 



#16 John Fitzgerald

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Posted 11 August 2020 - 09:07 AM

This is much about nearly nothing.  The bolt can be cut off and the cut end filed smooth,  or use washers.  Very simple.  Also, a half inch hole is less than a mm oversized for a 12mm bolt.  No problem.


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#17 ed_turco

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Posted 11 August 2020 - 10:55 AM

Bending washers to the curve would be ideal, but I have no idea how. I was thinking a square sheet before I knew which hole you were referring to. Washers sounds easiest and most predictable. They might bend the tube a bit. JB weld could fill some curvature on both sides.

You put a washer in a vise and use a hammer to bend it.  Shouldn't cost much to make loads of mistakes.
 



#18 Stardust Dave

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Posted 12 August 2020 - 02:43 PM

Tak North ,what is the structure shown in the pic?    I have a wild guess , could be wrong.



#19 Luke82

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Posted 12 August 2020 - 04:00 PM

Soyuz, 

 

If you want the bolt nice and snug in the hole consider a nylon shoulder washer.

You'll have to drill the hole out more to fit the should washer in... so steady hands for that part or you'll need an even bigger shoulder washer. 

Curvature of the scope may be an issue but I'm sure with a bit of heat you could get it to shape. 



#20 Starman81

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Posted 12 August 2020 - 04:06 PM

The addition of a couple washers did the trick. Due to the relatively large circumference of the tube and the small size of the washers, there is virtually no gap.

 

Thanks for all the recommendations. 




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