Fundamentals: Screws and Drivers (1/3)

In the previous blog post we have outlined most of the essential tools for the repair and maintenance of classic Nikkors. Now, we will be discussing the best application for these tools so that you will less likely to destroy your lens by stripping a screw head or misaligning your helicoids.

Just like everything else in life you may mess up in your first few projects and that is OK. In my case, I messed up three projects because there is just not a lot of online materials for this and any useful information out there are scattered or can be irrelevant at times. The lack of proper tools when I first started was also a big contributor to my failed projects since I thought that it would be just as simple as fixing your average kitchen appliance. The good thing is, I have managed to fix the failed projects now.

This guide is not going to be organised in any order and I will be updating it from time to time as I find new ways and remember anything that I have done in a previous project or find something in another person’s practice. A good deal has been discussed on the previous post so please refer to that as well and I will try not to repeat anything that can be found there.

Screws and Drivers:

The rule is to use the right type of screw driver for the right head. If the tip of the screw driver does not fit the screw’s head properly and there is play then you are using the wrong screw driver. Forcing your way into it will just strip your screw head so stop and find the right size or modify your own.

Of equal importance is the direction in which you are turning your driver. clockwise to tighten and counter-clockwise to loosen, always remember this – “lefty loosey”.

For the plus (+) drivers, if you stick to the JIS screwdrivers you will be just fine most of the time since the groove for JIS screws seem to be the same across the board, hence the JIS standard. I have never heard of anybody having the need to modify the JIS screw drivers at all.

Things can get trickier for minus (-) drivers as the groove seem to come in different widths and lengths. If the tip does not fit the slot perfectly then the tip is too loose and to make it fit properly you will need to grind the tip a bit until it fits. Just make sure that you grind it carefully so that you will not grind away too much metal from the tip and end up with a tip that is too big to fit in the slot/groove.

The shorter screw drivers are used for precision & comfort so that you will have more control and your wrist will have less strain since you are using your fingers to turn them.

The longer screw drivers are used for larger screws that have seized due to corrosion or locktite. They will provide more torque because you are using your wrists to turn them instead of your fingers.

Always press on the screw with the proper amount of pressure. If there is not enough pressure then there is a chance that you will strip the head of your screw. Putting too much pressure will lead to slippage since you will lose control of the driver and this will leave a scar on any surface the tip will scratch or stab you in the finger (it happened to me once).

The older Nikkor lenses have the tendency of having excessive amounts of loctite used on the bayonet screws (and elsewhere) and you should be very careful when working on these. There will be times when you would need to put a drop of acetone on the screw to loosen whatever they have used on the screw or just apply the correct pressure and torque to loosen them.  I used to heat the screw with a butane torch to burn whatever thread lock they used on the screw but since I started using the longer shafted Vessel drivers, I do not find this necessary anymore. This screw burning practice is a very common hack for auto mechanics (specially on rusted screws).

Be specially aware that screws come in different sizes in accordance to it’s use as was discussed in the previous blog post. Below are illustrations of these screws and where they are usually found.

IMG_1524Above is a picture of M1.7 screws used for extra strength, usually found in these parts.

IMG_1431This shows M2 screws that are typically found in the bayonet mount and nowhere else.

IMG_1440M1.4 screws are generally used for the rest of the lens. This is the standard size for Nikon.

Please don’t mind my speech and humour because hay fever and Jägermeister do not go well together. Also note that I burned part of the paint of the aperture ring while I was heating it. I was in an awkward position and I cannot see very well without my glasses. This is the sort of thing that can easily happen when you are not careful so I hope that this will serve as a warning to you. Botching up a repair is this easy. All in the name of education! Please read and watch this article on how to work with Nikon bayonet screws (IMPORTANT!!!).

Also of equal importance is the type of screw heads being used. Below is an illustration from Conex.

screwheadtypes_400

Generally, internal screws should be of a flat head type so that it is flush with the surface to avoid fouling anything. The oval screws are used for the outer cosmetic parts such as the machined aluminium grip. Pan head screws can also be found from time to time. The rest of the types shown are rarely used if ever.

The materials used for the screws come in different types as well. Nikon used good quality stainless steel screws back in the days before the Ai-S lenses era. From the Ai-S lenses era to the current crop of lenses, Nikon used cheaper screws made from cheaper materials that corrode with rust. It is also worth noting that lenses made early on the pre-Ai era are of the minus (-) type.

You should also be careful with the pitch of the screws. Pitch is the space between ridges in the screws threads. Usually, M1.4 screws will be 0.3, M1.7 screws will be 0.35 and M2 screws will be M4. Be very careful since using the wrong pitched screw will result in a ruined thread.

If a screw’s head is badly corroded or you have stripped it accidentally, you should only use a screw or bolt extractor to remove it. Always remember to buy the correct type irregardless of brand. The best that I have used is this one on the picture below:

IMG_1504

To use it, simply drill a hole that is 1mm-1.5mm deep on the screw’s head (and into the shaft) with your Dremel. Also make sure that you lubricate the spot with WD40 or alcohol so that the drill bit will not overheat or else it will dull the tip of the drill or snap. Drilling too deep into the screw will result in flaring of the screw and screw hole when you use the extractor so be careful.

Next, put the extractor on a hex screw driver and twist it the opposite way, and always remember the saying – “lefty loosey”. The screw extractor will bite into the drilled hole and use friction and torque to force the screw out. Used properly, you can even remove a headless screw. This is the cleanest way to remove any stuck screws. Avoid using gimmicky tools like Moody Tools’. They are just a waste of time and money (I bought a set) and it does not come with any documentation at all. It may work for some people but for what we want, it is useless and over priced.

The extractor that we just discussed can be bought online in Rakuten. You can use similar ones but just be sure that it is the 1mm type and is similar to what I am using.

To extract stuck screws with an exposed head that is taller than 1mm, a set of nejisaurus screw extraction pliers does a quick, clean and amazing job. Just make sure that you buy the smallest one. These are special pliers with a notch in the front part of the jaw to grab screw heads. I even managed to remove a headless screw with this once. So long as there is something that is exposed and is tall enough to grab, the nejisaurus will get it.

For screws that are so corroded that twisting it will just result in the head snapping off and leaving the rest of the screw’s shaft inside the hole, start by drilling the hole with a drill bit that is slightly smaller than the hole or screw, as an example use a 1mm bit for a 1.4mm hole. Doing this will bore through the stuck screw shaft. Next, use a hand tap that is similar to the size of the hole to cleanup any stuck material or left over screw parts and to repair the damaged threads.

As an alternative to the technique just described above, you can also drill the hole with the correct diameter and tapping it with a slightly larger tap. For example, for a 1.4mm screw hole use a 1.4mm drill bit and tap it with the next bigger sized screw (1.7mm). Doing this will turn the hole into a 1.7mm hole so the screw size will also change. You can also do this for the threads that are so badly worn that the right sized screw turns up being too lose and will not even engage the threads, resulting in a free-turning screw.

Just remember that these techniques are best done on parts and surfaces of the lens that will not be seen since they will obviously look improvised and should be used as a last resort.

There will also be times when the correct screws cannot be obtained and you are only left with modifying a screw to fit. What I do is I put the screw in the Dremel’s chuck and shape the screw with a file and sandpaper with the Dremel acting as a makeshift lathe.

For working with the Dremel corded rotary tool, it is advisable to purchase the mediocre Dremel Workstation. It is basically a small drill press but will also hold the Dremel in place while you use it as a grinder. It is not perfect because it wobbles here and there but there are no cheaper alternatives at the moment.

To be continued…

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Helping support this site will ensure that this will be kept going as long as I have the time and energy for this. I would appreciate it if you just leave out your name or details like your country and other information so that the donations will totally be anonymous it is at all possible. This is a labor of love and I intend to keep it that way for as long as I can. Ric.

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66 Comments (+add yours?)

  1. orangeelephantphoto
    Dec 29, 2015 @ 05:17:15

    Useful & interesting, thanks!

    Reply

  2. richardhaw
    Dec 29, 2015 @ 06:45:06

    Thanks!!! The next one will be on the topic of lubrication. I will see if I can write it tonight. (If I finished repairing the 80-200 f/4 ai-s early)

    Reply

  3. Ron
    Dec 29, 2015 @ 19:25:39

    Great stuff, thanks Richard 🙂

    Reply

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  59. Carlos Fernandes
    May 16, 2017 @ 21:38:33

    Hello Richard

    You should also be careful with the pitch of the screws. Pitch is the space between ridges in the screws threads. Usually, M1.4 screws will be 0.3, M1.7 screws will be 0.35 and M2 screws will be M4.

    Let me ask a question about this sentence: “M2 screws will be M4”. Is this correct ?
    What is usually the thread for the M2?

    Thanks
    Carlos

    Reply

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