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help! Stripped screw head in skywatcher focuser - trying to upgrade

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#1 laurelg9

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Posted 27 July 2021 - 02:03 PM

Ugh.  I purchased a two-speed focuser upgrade that came today and in the process of trying to remove the cover for the focuser, discovered that one tiny screw is stuck in there and the head is dangerously close to getting stripped. I'm unsure how to proceed. Can I spray WD-40 into that part of the focuser and not have it mist all over my secondary? or in the OTA?  

 

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#2 Couder

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Posted 27 July 2021 - 02:26 PM

Many screwdrivers are worn. I suggest getting a new or newer one, be sure it fits tightly. There are several sizes and types of Phillips screws. Take one with you to the store and make sure the new one fits. Hold pressure on the handle, turn slowly. If it is stubborn, sometimes it helps to try and tighten a tiny bit first. Doubt any liquid can get past the head. If you're concerned about it getting all over, don't spray - put a dab on a toothpick and put that against the bottom of the screwhead. (Hold it so the screw is facing head up towards you.)


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#3 ScottW

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Posted 27 July 2021 - 02:26 PM

Laurel,

 

Take the focuser off the tube.  Heat the plate with a hairdryer.  

Place screwdriver on head of screw apply torque and tap the handle end with a hammer.  Somewhat like an impact wrench. 

Or use a hammer drill and phillip bit.

Liquid Wrench might work better than WD-40.

 

Scott


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#4 Mike G.

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Posted 27 July 2021 - 02:56 PM

worse comes to worse, you can drill the head off then remove the plate.  at that point you should have enough of the threaded shaft sticking up to grab with some vicegrips and turn it the rest of of the way out.  but try the other methods first.



#5 photomagica

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Posted 27 July 2021 - 03:12 PM

Couder and Scott have provided great advice. I've had to deal with lot of stuck screws. For fine mechanisms (anything on  a telescope), SuperLube spray tends to be a very good penetrant. I orient the mechanism so that the screw is facing up, drop the liquid on with a Q-tip and leave it overnight. Before attempting screw removal I wash the penetrant out of the screw slots with alcohol and dry the slots with canned air, since I don't want the screwdriver to slip. You can also sprinkle a tiny amount of very fine carborundum in the slots, which will noticeably increase the grip on the driver blade.

 

I also replace soft screws, frequently found on Chinese equipment or even other equipment since China made fasteners are everywhere, with a better grad of stainless screw if I can.

For extreme cases I have a hammer driven impact screwdriver. 

 

Bill



#6 Tangent

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Posted 27 July 2021 - 03:43 PM

Looks like a combination (slotted + philips) head round screw.  Try using a slotted screwdriver with a head size that fits the screw properly - buy a new screwdriver if needed, or grind/file an existing oversized screwdriver so that it fits.   When you turn the screwdriver, make sure to use some strength to press it into the screw so that it doesn't cam out of the screw as you rotate the screwdriver.  It can help to wear rubber-palm gloves to get a good grip on the screwdriver.

 

A penetrating lubricant should not be necessary, but if you ever do need lubrication in a tight space (or on a delicate piece of machinery like a telescope), squirt a little lubricant into a small container, then transfer a small amount using the end of a dental pick or toothpick.



#7 spacemunkee

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Posted 27 July 2021 - 03:54 PM

Another possibility, if you have any, is a square tip driver. Some screws are made to accept like ones on electrical devices, or screw may be just right to accept one with a tight fit, and won't want to push out like a Phillips. Worth a shot, but of course don't just end up doing more damage if it seems iffy..



#8 ScottW

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Posted 27 July 2021 - 04:13 PM

Laurel,

One more thing to try.

Reinstall and snug all the screws and then try to loosen the stuck screw.  

 

Good luck,

 

Scott



#9 chanrobi

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Posted 27 July 2021 - 04:14 PM

First,

 

Do NOT use Wd-40.

 

Second, get an impact driver set with a philips head that is the *correct* size. This will allow you to apply maximum pressure down the length of the bolt via a hammer and it will turn the bolt for you at the same time.

 

Do NOT, I say again, do NOT try to turn that bolt any further without an impact driver!

 

https://www.youtube....h?v=xIkpjfR_LD0


Edited by chanrobi, 27 July 2021 - 04:16 PM.


#10 chanrobi

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Posted 27 July 2021 - 04:15 PM

Laurel,

 

Take the focuser off the tube.  Heat the plate with a hairdryer.  

Place screwdriver on head of screw apply torque and tap the handle end with a hammer.  Somewhat like an impact wrench. 

Or use a hammer drill and phillip bit.

Liquid Wrench might work better than WD-40.

 

Scott

There is a tool that does exactly this, but x1000 better, see above
 



#11 laurelg9

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Posted 27 July 2021 - 04:33 PM

Thanks, all.  I came back to this thread more than once to try things.  I worked it loose, and soon will have a really nice upgrade of a 2-speed focuser.  And, it's clear tonight, excepting some wildfire smoke high up.  


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#12 laurelg9

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Posted 27 July 2021 - 05:03 PM

Though -- lol -- I may need to start another thread. I put this all back together and the focuser tube rattles in the contraption that holds it.  I can tighten the screw to tighten the tension, but then the focuser won't go up and down.  What gives? Argh. 



#13 MitchAlsup

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Posted 27 July 2021 - 05:23 PM

Though -- lol -- I may need to start another thread. I put this all back together and the focuser tube rattles in the contraption that holds it.  I can tighten the screw to tighten the tension, but then the focuser won't go up and down.  What gives? Argh. 

Yes, indeed, you use the torque on each of the 4 screws to 

a) take up the slack,

b) set focuser knob friction and stiction.

 

So snug up each screw a little at a time, then feel the draw tube and rotate the focuser knob and decide to tighten a bit more of to loosen a bit. The final set point of these screws for proper tension will be on-the-order of 2-3 degrees of rotation on the screwdriver body.

 

Do not be surprised if it takes you 2 or 3 nights before you get it to the tension where "you never need to touch the screws again". And when you get to that point, you an fix the screws with a tiny drop of nail polish on each screw to hold it where it is.


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