NikonGear'23
Gear Talk => What the Nerds Do => Topic started by: stenrasmussen on February 15, 2016, 08:53:49
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Another project came in.
Said lens suffers from loose brass collar/nut that currently lives a life rolling around on the aperture blades. Suffice to say the lens inoperable and my task is to try and fix it.
If anyone has a diagram or service chart/manual to share it would make my life easier. I will however get going and hopefully I can get to the bottom of the problem. Will post pics and updates here in due course.
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currently looking for a guide. looks like there are non available even on japanese sites :o :o :o
i will tell you once I saw something
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currently looking for a guide. looks like there are non available even on japanese sites :o :o :o
i will tell you once I saw something
Much appreciated :)
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In addition to your extensive Lens Medical Studies, you might have to learn Japanese, Sten :D
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i can write to sigma and request a repair guide. night worth a try :o :o :o
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In addition to your extensive Lens Medical Studies, you might have to learn Japanese, Sten :D
I am like a toddler...just looks at pictures and pretend I can read ;D
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i can write to sigma and request a repair guide. night worth a try :o :o :o
THAT would be an interesting exercise!
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So the little brass-fecker has been found, as has its securing screw. I am
hugely impressed by the build quality of this Sigma. Metal and such does not stand back related to Nikkors (real Nikkors).
Here are a few pics showing the process. The lens needs to be assembled again and I'll report back with end result.
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that looks stupid, how did that cam roller get off it's thread :o :o :o
maybe somebody forgot to use threadlock ::)
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that looks stupid, how did that cam roller get off it's thread :o :o :o
maybe somebody forgot to use threadlock ::)
That's the thing - I couldn't spot any remnants of threadlock stuff on the screw. Also, there's only ¼ of the screw length holding back the leverage from the remainder ¾ of the screw.
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Don't over-tighten that screw!
3 threads in is not enough for such tiny threads, normal design says depth of threads must be at least 1.5 x the diameter,,,
Maybe the lens was dropped, that's the usual case for these to break or loosen,,,
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Don't over-tighten that screw!
3 threads in is not enough for such tiny threads, normal design says depth of threads must be at least 1.5 x the diameter,,,
Maybe the lens was dropped, that's the usual case for these to break or loosen,,,
I know Erik, the lessons learned from previous overtightened screws have taught me to add just enough torque on the JIS.
A drop situation might very well be the cause.
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or maybe vibration (car/train/plane) :o :o :o
no thread locks whatsoever!
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I am happy to report that the lens is back in working order!
No threadlock added as I opted to return the lens as was - sans the dust between the lens elements and those loose parts :)
A couple of tips:
- There is a long thin flex cable that is best fastened before the circuit board is secured in place with the two screws (see pic below).
- There is a difference to the four screws securing the rear light baffle and contact block. The two going into the metal of the contact block has finer threads than the other two with coarser threads that goes into the plastic light baffle (pic below).
A couple of pics showing how I do the job with the flex cables added as well.
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Well done Sten!
No need to remove dust in lenses, doesn't matter since the image is not formed inside the lens, for ultra wide angle lenses a clean front element is mandatory and for most lenses a clean rear element is required.
I just love the reference with two different types of screws in the light baffle ;D - There are so many different screws all over that lens your not supposed to mix up ;D
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Thanks Erik!
Personally I am not obsessed with dust inside a lens but since this one goes back to my dealer for "used sale" I want to make the lenses I service as nice as possible.
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Impressive work.
Still don't understand why the screws have to be all different... and that's not only Sigma...
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The materials demand different threads to work, fine threads don't work in plastic, they get ripped out du to the area of material being too little - so you need more thread area, the threads are therefore deeper and longer in-between, a steeper angle that is.
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The materials demand different threads to work, fine threads don't work in plastic, they get ripped out du to the area of material being too little - so you need more thread area, the threads are therefore deeper and longer in-between, a steeper angle that is.
Sure Erik, metal and plastic do require different threads.
But how to explain different threads to metal, and not talking of fine vs coarse pitch, but metric with unc; bsw with unc, and so on...
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I don't know if we should make a new topic, we can always split it later if needed I guess,,,
Metric with unc; bsw with unc
BSW was the first real standard for threads,,, British
UNC was based on Inch as well but American US - Metic was based on Meters, European
Here goes quickly some of the differences as to understand the basis for some differences:
First threads where custom made locally, obviously this created some issues when replacements where needed. So entry of Standards BS US DIN ISO JIS etc. Also some still are by company, country, region or global...
Our company, ship engines, use selected few thread sizes, they come in a Standards Book, to obtain as few variants as possible, less stock needed and less spares needed in design, models in 3D drawings, in the factory, in stock all over world and on the ship, same goes for the tool sizes etc. since our engines are build in Asia we use a base of standards that is a mix of JIS and ISO, old DS Danish Standards and even ship standards,,,
The use of the actual threads demand even further differences, like the ultimate in strength are trapezoidal threads they have a very large area similar to with the plastic, but if used in metal naturally the screw can also have the trapezoidal shape.
We use a special variant of trapezoidal threads since we tighten the long screws, studs, with hydraulic jacks, so the nut must be able to be turned only using hand tools while the stud is stretched to obtain the desired pre-tension - Therefore we have a company standard for that thread, and the allowed variant sizes.
The car industry has used Inch sizes and some still do, they have a more coarse thread size generally, preferred since easy disassembly many years later, rust etc. is more easy but also re-use of assembly tools as well as spares like above is a huge consideration,,,
For Aircraft you need low weight but high strength so the design and solution is a shorter bolt and nut with finer threads, less steep angle to get the number of threads engaged high to carry the load,,,
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It now becomes obvious to me why tape is such a universal adhesive/fastener. Must be the reason why the little Nikkor 18-55 is taped together inside ;D
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He he yes! ;D Actually adhesive tape is used in almost all Nikkors,,,
Usually to hold some parts of the focus ring together or to hold a thin metal shield into position under the rubber of the zoom ring :o
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I don't know if we should make a new topic, we can always split it later if needed I guess,,,
Metric with unc; bsw with unc
BSW was the first real standard for threads,,, British
UNC was based on Inch as well but American US - Metic was based on Meters, European
Here goes quickly some of the differences as to understand the basis for some differences:
First threads where custom made locally, obviously this created some issues when replacements where needed. So entry of Standards BS US DIN ISO JIS etc. Also some still are by company, country, region or global...
Our company, ship engines, use selected few thread sizes, they come in a Standards Book, to obtain as few variants as possible, less stock needed and less spares needed in design, models in 3D drawings, in the factory, in stock all over world and on the ship, same goes for the tool sizes etc. since our engines are build in Asia we use a base of standards that is a mix of JIS and ISO, old DS Danish Standards and even ship standards,,,
The use of the actual threads demand even further differences, like the ultimate in strength are trapezoidal threads they have a very large area similar to with the plastic, but if used in metal naturally the screw can also have the trapezoidal shape.
We use a special variant of trapezoidal threads since we tighten the long screws, studs, with hydraulic jacks, so the nut must be able to be turned only using hand tools while the stud is stretched to obtain the desired pre-tension - Therefore we have a company standard for that thread, and the allowed variant sizes.
The car industry has used Inch sizes and some still do, they have a more coarse thread size generally, preferred since easy disassembly many years later, rust etc. is more easy but also re-use of assembly tools as well as spares like above is a huge consideration,,,
For Aircraft you need low weight but high strength so the design and solution is a shorter bolt and nut with finer threads, less steep angle to get the number of threads engaged high to carry the load,,,
Interesting insight
I'm curious about the start of the threads, a number of years ago cross threading was a problem I would find often , nowadays is very seldom, I wonder do the start of the screws has this been improved or with time I'm just being more careful
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Tools for making the threads have improved a lot, all quality screws today are rolled between dies flat or round.
One of the leaps in technology was the Torx instead of Heagon, Phillips and JIS screwdriver design for the bit, suddenly the machines/robots could spin faster and hold on to the screw by itself and not risking jumping out, there is a huge amount of area between the bit and screw so much more torque can be transferred and with very little wear on the Torx bit, each ot the Torx 'waves' are also angled at the end of the bit as to catch the Torx 'hole' in the screw head evn while rotating at high speed,,,
Now that demands a better 'running in' where the screw actually catch the thread in the hole, that's my best guess as to why,,,