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How to avoid stripping Screws when disassembling a Camera


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#1 Terry Mester

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Posted 06 September 2010 - 10:05 PM

How to avoid stripping Screws when disassembling a Camera

I want to share with you three of my techniques to avoid stripping screw heads when opening up a camera. Firstly, what you need to do is FREEZE the screw head with ICE. To prevent the camera from getting wet, just place the ice cube into a plastic sandwich bag, and push that against the screw head for about 30 seconds. Freezing will make the metal harder, and less likely to strip. In addition to making the screw harder, freezing also causes the metal to shrink a bit which makes it easier to unscrew. You will need to keep re-freezing it every 30 seconds until the screw comes loose.

My second technique when unscrewing a stiff screw is to not apply constant turning / torque. Constant turning is what will lead to the screw head stripping. When unscrewing a stiff screw, you need to use QUICK JOLTS. You accomplish these jolts by only very briefly applying the turning / torque with the screwdriver for only a fraction of a second at a time, and then you quickly let your hand loose on the screwdriver handle to stop the turning. These brief turning jolts, combined with freezing, will eventually jar the screw loose without stripping the head. For my third technique, it is also necessary to push the screwdriver VERY HARD into the screw head in order to prevent it from slipping. The screwdriver slipping is what wears down and strips the screw head, but hard pressure avoids this.

I want to make a comment on those tiny screws which hold the lens dials onto the lens. Those tiny lens dial screws are likely "headless" set screws, and only consist of the cylindrical screw body with a groove on the end for the screwdriver. These screws are also likely only threaded into the dial itself, and only apply "pressure" onto the inner lens case to hold the dial in place. Those lens dial screws are also probably glued into place to keep them from coming loose -- so you need to pick away the glue before unscrewing them. After screwing them back into place, you can use a toothpick to apply a small amount of paper glue on the end which will keep them tightly in place.
[Note to novices: you turn the screw to the LEFT (counter-clockwise) to unscrew it. Remember the phrase: Righty Tighty - Lefty Loosey. It is extremely unlikely that you'll come across a reverse threaded screw that turns the opposite direction.]

There might be some screws hidden behind labels -- so you may need to carefully pry away some labels. Use a piece of masking tape to securely hold the screws in the order you remove them -- they're tiny and you don't want to lose any of them. These techniques worked with 100% success for me when removing all necessary screws to open up my Super8 camera, and they will also work for you. Good luck! :)
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#2 Sanjay Sami

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Posted 06 September 2010 - 11:18 PM

How to avoid stripping Screws when disassembling a Camera

I want to share with you three of my techniques to avoid stripping screw heads when opening up a camera. Firstly, what you need to do is FREEZE the screw head with ICE. To prevent the camera from getting wet, just place the ice cube into a plastic sandwich bag, and push that against the screw head for about 30 seconds. Freezing will make the metal harder, and less likely to strip. In addition to making the screw harder, freezing also causes the metal to shrink a bit which makes it easier to unscrew. You will need to keep re-freezing it every 30 seconds until the screw comes loose.


You can also use Freeze Spray. If you dont have freeze spray you can invert a can of dust off and spray the propellant (as long as it does not spray on the coated lens elements) and use that as a freeze spray.
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#3 Sanjay Sami

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Posted 06 September 2010 - 11:26 PM

You can also use Freeze Spray. If you dont have freeze spray you can invert a can of dust off and spray the propellant (as long as it does not spray on the coated lens elements) and use that as a freeze spray.


Incidently, freeze spray is basically dust off with a straw connecting the nozzle to the bottom of the can, so that rather than spraying the vapour collected at the top, it sprays the liquified gas.
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#4 Dom Jaeger

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Posted 07 September 2010 - 02:12 AM

Probably the most important factor in removing screws without stripping the heads is the tool used. It's crucial to use the correct screwdriver size to fit the screw, whether slotted, phillips head or pozidrive. With slotted countersunk screws the driver head should be slightly smaller than the slot, to avoid scraping against the countersunk seat.

The driver tip should also be undamaged. A phillips head screwdriver with the tip ridges all chewed or a slotted one with the corners rounded is a stripped screw head waiting to happen.

The easiest to damage are hex or allen screws, which can easily be rounded out, especially the tiny ones. Make sure you don't use an imperial driver on a metric hex or vice versa.
If the allen key or hex driver tip is starting to round off it's time to grind a new tip or buy a new one if you don't have a grinder. Much easier than drilling out the screw, I can assure you.

A lot of camera screws are held in place with loctite or varnish. The best technique to loosen them is acetone (nail polish remover) and then maybe a heat gun.

I generally find heat a better option than freezing, especially steel screws in aluminium. The coefficient of expansion for aluminium is twice that of steel so the screw hole expands more than the screw. Also freezing with ice can only alter the screw temperature by probably 15 or 20 degrees Celsius at most, and it can be hard to only cool the screw head. If you cool the surrounding aluminium it will shrink more than the screw will.

For corroded screws I give them a drop of a rust inhibitor/metal lubricant like CRC 2-26 and let them soak. If they still stick I'll use heat.

The tips about using brief jolts and pressing down hard are spot on.

If you do strip a screw it is probably best to take the camera to a professional. Drilling out small screws is very tricky. You need to drill precisely down the centre of the screw and then use an easy-out. The screw is almost always harder than the surrounding metal so a deviant drill easily veers off and destroys the threaded hole. And you also need to keep the swarf out of the mechanics.

A word of advice about film cameras in general - if you see a screw that has been sealed with a drop of paint it is often a critical adjustment screw and should not be tampered with. I would also advise against undoing the set screws on lens barrels unless you know what you're doing - sometimes they too are holding in place a critical setting.
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#5 John Sprung

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Posted 07 September 2010 - 03:17 PM

This is by far the best stuff for anything that's stuck, corroded, or rusted:

http://www.kanolabs.com/




-- J.S.
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#6 Tom Jensen

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Posted 07 September 2010 - 06:12 PM

Heat always worked for me as well. You have to bust loose Locktite and that can be pretty tough. Also have replacement screws is pretty handy.
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#7 Terry Mester

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Posted 08 September 2010 - 12:01 AM

Probably the most important factor in removing screws without stripping the heads is the tool used. It's crucial to use the correct screwdriver size to fit the screw, whether slotted, phillips head or pozidrive. ...

Yes, you definitely need the proper screwdrivers. I purchased a set of precision screwdrivers -- down to 1mm -- before beginning the job. The Lens Dials were 1mm screws.

...
I generally find heat a better option than freezing, especially steel screws in aluminium. The coefficient of expansion for aluminium is twice that of steel so the screw hole expands more than the screw. Also freezing with ice can only alter the screw temperature by probably 15 or 20 degrees Celsius at most, and it can be hard to only cool the screw head. If you cool the surrounding aluminium it will shrink more than the screw will. ...

The more the screw and case shrink the better. It doesn't matter if they shrink at different rates. The more the shrinkage, the more the bonds of friction will break, and the looser the screw will be in the seat. The hotter the metal is, the softer it is, and the more likely to warp or break. This happened to me when heating a rusted bolt on my car with an acetylene torch. The bolt sheared off. I had no problems with freezing my camera. :D

...
I would also advise against undoing the set screws on lens barrels unless you know what you're doing - sometimes they too are holding in place a critical setting.

It was necessary for me to remove the outer Lens in order to remove the front cover of my Sankyo Super CM 400. Although I trust myself to do this delicate job, many people should best not try such work. :o
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#8 Chris Millar

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Posted 08 September 2010 - 03:07 AM

Big to differ on the reverse threads - they are reasonably likely in cine cameras (compared to still at least)
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#9 Alessandro Malfatti

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Posted 15 September 2010 - 08:30 PM

Why not use an upside-down compressed air can, and let a few drops fall on the screw in order to freeze it? The liquid evaporates almost instantly, so no worries getting the camera wet.
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#10 Terry Mester

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Posted 16 September 2010 - 09:58 PM

How "cold" in terms of "temperature" is this spray? I can't see this spray as doing anything more than just freezing the screw head. You would need the whole screw to be frozen. An ice cube has a very large capacity to suck the heat out of the screw and seat, and you don't need to wait for the screw to dry to unscrew it. Delay results in the metal warming back up.
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#11 Alessandro Malfatti

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Posted 17 September 2010 - 04:19 PM

How "cold" in terms of "temperature" is this spray? I can't see this spray as doing anything more than just freezing the screw head. You would need the whole screw to be frozen. An ice cube has a very large capacity to suck the heat out of the screw and seat, and you don't need to wait for the screw to dry to unscrew it. Delay results in the metal warming back up.


Hell, you tell me:

If the can is held upside down, then its contents are expelled as a liquid. This liquid evaporates very quickly at standard temperature and pressure, chilling anything in contact with it. This process can produce very cold temperatures, easily sufficient to cause frostbite. Similar cans with dip tubes are marketed as "freeze spray," and will expel liquid when held right side up.


It's about 78% Nitrogen, 20% Argon and 2% other stuff. I think it's pretty cold. ;)
But you can always try it on yourself...
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