NikonGear'23

Gear Talk => What the Nerds Do => Topic started by: Seapy on February 06, 2018, 10:31:10

Title: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 06, 2018, 10:31:10
Not sure if this is the right place or under 'Lenses' but decided on balance here.

My 20mm took a tumble while attached to my D3, D3 is fine, lens not so good.  It crunched the front rim and it rattled, sheared a screw inside.  I tried to unscrew the front to remove the front but just made it worse, the screw head was jamming the AF and since I needed the lens I dug a hole in the already damaged front to allow the screw head to escape.  The damage is ugly.

(https://farm5.staticflickr.com/4755/39880376931_68c3cf27cf_b.jpg)

Now I have my lathe up and running, I have decided to make a new front for the lens.  I have found by removing the rubber grip on the focus ring and focusing at infinity I can access the three screws which retain the front piece of the lens.   The front piece is very simple and only about 10mm long by about 67mm diameter.   I don't have a lens hood for this lens but I believe the correct hood is very shallow.  Looking at my 16mm fisheye it's lens hood is built in, with a slip on metal cap which is very handy and quite robust.

I am considering making a new front which has a similar built in lens hood with a slip on metal cap.  This provides some protection for the front element and perhaps helps shade the lens somewhat from direct sunlight.  My preferred stock is 25mm thick so that would allow for a hood about 15mm deeper than the original front of the lens.  Is that worth doing?  I *could* use different stock and have a much longer hood but the 20mm lens is pretty wide on FX, I anticipate some vignetting or even loss of image at the corners if I go too long.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on February 06, 2018, 11:39:12
The usual approach is to cut a piece of thin cardboard, draw a line while looking through the viewfinder for 1/4 of the circumference and copy and mirror it around the lens for a full version, trim cardboard template until satisfied, test stopped down f/22 at close and far, CRC,,, transfer template to metal,,,
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on February 06, 2018, 12:30:45
I can try and ask for replacement parts :o :o :o
I am going to the Nikon warehouse soon anyway
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on February 06, 2018, 13:47:58
I'm pretty sure this is not a case of path of least resistance,,,  :o :o :o
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on February 06, 2018, 13:53:55
This is a shortcut to creating a template:


http://www.lenshoods.co.uk/hoods/Nikon-AF-Nikkor-20mm-f-2.8-D.php
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 06, 2018, 14:47:00
I'm pretty sure this is not a case of path of least resistance,,,  :o :o :o

 ;D Not looking for a standard solution!

Want to spend a few hours making swarf.

Thank you for the link Eric, good starting point, it will be a good guide for the cut outs, I think I will keep the flat top profile similar to the 16mm f2.8 fisheye, and parallel so I can make a and fit a matching slip on cover.  I have lot's of nice aluminium.  ;D

I had been fretting about cutting the filter threads, two threads 62mmØ at  0.75mm pitch my lathe can do metric but only 'officially' down to 1mm pitch.  However after spending a few hours with Excel spreadsheets I discover that ~43 threads per inch is mighty close and I can find a combination from my change wheels that gives me that... But I don't really need a filter thread, I don't use filters usually and if I make an integral lens hood with slip on cap, I don't even need a pinch lens cap.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 06, 2018, 14:50:20
I can try and ask for replacement parts :o :o :o
I am going to the Nikon warehouse soon anyway

Many thanks for the offer Richard.

On this occasion I don't feel that's my path.  Maybe one day I would really need something special?
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 28, 2018, 21:05:43
Well, my 20mm f 2.8 D has sat on my desk long enough, I took some measurements and headed for the shed...

I cut a blank then realised it had a hole in a bad place so cut another.  Faffed about mounting it in the lathe so it could be reversed and retain accurate alignment, it stays within 3 thou about 0.09mm that's good enough for me.  I have roughed it out and pretty well finished the back of the part.  I have decided to make the lens shade 75mm OD and pretty shallow.  I will assemble it and if need be I will relieve it as required to avoid any corner vignetting.

Mounted on a length of scrap shaft, roughing out the outside.

(https://farm5.staticflickr.com/4712/40498938022_bac839df68_b.jpg)

The original black plastic lens front propped behind the new part.

(https://farm5.staticflickr.com/4747/40541556301_c0f34be261_b.jpg)

This is the lathe cutting metal into swarf!  ;D

(https://farm5.staticflickr.com/4712/40498938022_bac839df68_b.jpg)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on February 28, 2018, 22:29:10
Looks like s good shape is already coming to life ;)


Remember to make the inside rippled or do you plan to use flocking,,,


I also prefer the flat top and bottom like on the Fish


Nice when you put the lens front end down ;)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Akira on February 28, 2018, 22:31:36
Robert, now you started to make us wonder again!
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 28, 2018, 23:13:57
Looks like s good shape is already coming to life ;)


Remember to make the inside rippled or do you plan to use flocking,,,


I also prefer the flat top and bottom like on the Fish


Nice when you put the lens front end down ;)

Plan to put grooves in like the plastic original,  then hopefully anodise mat black.  I would like to make a Fish cap like the 16 with the Nikon logo... Face down it won't fall over, that's for sure!

I am told it's best to store these lenses face down to help avoid oil on the blades, is that right?
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on February 28, 2018, 23:14:58
Robert, now you started to make us wonder again!

That's the plan Akira! LOL   ;D
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Matthew Currie on March 01, 2018, 00:32:00
Nice recycling of dead ball bearings there too.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 01, 2018, 01:07:52
LOL, throw nothing away...  Well keep handy bits of metal anyway.

I needed a 14mm spacer and that bearing is 14mm bore, perfect.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 01, 2018, 08:13:18
.....I am told it's best to store these lenses face down to help avoid oil on the blades, is that right?


I would say it doesn't matter  :D
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on March 01, 2018, 09:30:50
temperature will probably have a bigger impact  :o :o :o

modern lenses shouldn't matter except for probably the 55/2.8 or lenses that are known to be troublesome with oil on iris.

it is true for lenses that were lubricated the old way using whale oil or other less stable old style grease. i am cleaning older and older lenses these days (pre-war Zeiss) and you can see the pattern on how the grease migrated just by looking at the mold marks where the fungi has left marks after eating the oil.

storing a lens with the aperture wide-open or close will also have an impact. i thought that this was an old wives' tale until I began working on the first Nikkors and older RF lenses. for automatic aperture lenses, the spring will weaken when left tense for a very long time, I had to replace springs a few times because of this. for RF lenses, the iris may be stuck with corrosion from the oil when stored wide-open. i know this sounds silly but I can now say that there is some truth to this.  ::) unfortunately, some people will forget about a lens and the next time the lens is exercised will be a couple of decades later...by a grandson or stranger.  :'(
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 01, 2018, 09:53:34
Thank you both, the trouble with things like this is that as Richard says, it is a long term thing.  The open - closed iris had not occurred to me, I can see the reason it could matter, springs can take a 'set' if left expanded or compressed for long periods, age hardening may also play a role.  Are you saying better open, or better closed?
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 01, 2018, 10:51:22

,,,,,,,storing a lens with the aperture wide-open or close will also have an impact. i thought that this was an old wives' tale until I began working on the first Nikkors and older RF lenses. for automatic aperture lenses, the spring will weaken when left tense for a very long time, ,,,,,




Yes it does loose tension over time from not being used, however it also loses tension from use, it's called creep.


So saying it is one or the other from storage open or closed,,, difficult/impossible call IMHO,,,
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on March 01, 2018, 11:08:11
Thank you both, the trouble with things like this is that as Richard says, it is a long term thing.  The open - closed iris had not occurred to me, I can see the reason it could matter, springs can take a 'set' if left expanded or compressed for long periods, age hardening may also play a role.  Are you saying better open, or better closed?

depends, really. so long as the spring isn't tense. :o :o :o
the "old wive's tale" that i have been hearing since the 80s was to store the lens with the iris left at mid-range of the opening, maybe about f/5.6. i shrugged it off as BS before.

I am currently servicing an early Contax 2a from 1951(?) and a few weeks ago, a couple of Nikon S's and some springs on the Nikon S's had to be re-tensed to make them thing work. I was referring to the high speed pawl and the long spring underneath. on the Contax, the spring for the slow governor has lost its tension so its a stop faster than ideal. these cameras were probably stored for decades like this and this is the result.

i grew up in a watch repair shop where I was an apprentice and we would sometimes get watches older than some countries in Europe, Asia or Africa and some of the springs just lost their tension so the escapement won't work anymore. I guess it is inevitable. nothing lives forever trouble-free, including machines.

of course, constant use like what Erik mentioned can also contribute to this. our neighbor next door is a camera shop and they did spring changes or re-tensing on the then-current-model FMs, etc on a constant basis (from pros i assume).

I asked somebody at Nikon and he advised that storing a lens with the bayonet facing down is generally thought of as the best because it is structurally the strongest part of the lens. this has nothing to do with oil but probably more to do with the delicate gearing of current AF lenses specially if they are heavy. ::)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 01, 2018, 11:32:42
Yes I agree :)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on March 01, 2018, 11:43:37
i asked him this because there was a very long discussion on a forum that I was active in long ago about storing lenses. the biggest no-no according to him is storing new AF lenses on its side specially the ones with VR as they can be misaligned. he also told me that the VR element is so sensitive that it can get misaligned just through constant use and will have to be sent to Nikon to re-calibrate on a regular basis.  :o :o :o maybe this is true if you are a pro. i went to the Nikon warehouse for repairs and true enough, the lenses are not stored sideways but up or down. the ones on the workbench are a different story, maybe because they will not be stored like that for a long time ::) i got into the storage room because i wanted to try their 50/1.2 but thats a different story.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 05, 2018, 18:10:52
The lens front is now finished apart from the cap and final coating.

Cutting the petals was tricky, I made a little template for the cut outs but in the end I had to do it by measurement.  I couldn't get rid of the vignetting at the corners.  I needed to make the cutouts symmetrical by measurement.  That worked by hand filing and repeatedly test fitting.

(https://farm5.staticflickr.com/4742/40595210122_0eb3b9057f_b.jpg)

(https://farm5.staticflickr.com/4619/39926752694_a33704fc51_b.jpg)

(https://farm5.staticflickr.com/4751/39741223345_e4e85c0657_b.jpg)

The lens shade looks a little scrappy in these pictures but it's mostly reflections, rubbed down and painted I am sure it will be quite nice.  My 16mm fisheye is quite battered and scraped around the front end so it should match!.

What would anybody recommend to paint the lens hood with?  I was intending to get it anodised but I wonder if a matt black spray paint might be better?

I am intending to make a push on (clip on?) cap similar to  the 16mm Fisheye cap.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Matthew Currie on March 05, 2018, 19:22:41
Matte black paint doesn't wear terribly well, but on the plus side it's dead easy to freshen up.  I've used brush-on semi-gloss Rustoleum to clean up the edges of AI-milled lenses and the like, and it works pretty well there.  I would guess that a similar thing in spray would be pretty effective here as long as you don't worry about the edges wearing off almost immediately.  If you wanted to get fancy you could even do the outside with more gloss than the inside.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 05, 2018, 19:36:56
Thanks Matthew,  I think I have some black Rustolium in aerosol.  I use Rustolium quite a bit, I have some primer which is specially for aluminium.  I will try it!

I forgot to mention above that I have ribbed the inside of the hood to help reduce the internal reflections, hopefully.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 05, 2018, 20:14:52
Humbrol Enamel is quite strong, and not IR reflective  ;)

33 is Matt Black
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Hugh_3170 on March 06, 2018, 02:20:37
I have also had good results with Humbrol 33 (Matt Black) on top of aluminium etch primer (I got some such primer from a panel beater/motor car painter).  Rub the primer down really lightly with very fine grit paper - around 800.

An alternative is blackboard paint for larger areas, but I do like the matt Humbrol - it is good for hiding witness marks in the metal.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Akira on March 06, 2018, 02:39:24
I'd like to see it finished in black anodize with the internal part painted in mat black using either of the suggested paint.  :)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on March 06, 2018, 02:59:29
Humbrol's matte black is better than Tamiya's. Testrol's not so bad too  :o :o :o
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 06, 2018, 10:05:58
Akira's option seems to me the best way, I am planning to anodise my pano head but cost is a factor which is getting in the way right now.

I will look at anodising kits first but rather lack confidence to get involved in chemistry.  Don't want to ruin the appearance of my work by spoiling it with a shoddy anodising job.

You can get aerosol etching primer, Rustoleum themselves do an aluminium primer but it's brush on, sort of rubbery?  It balls up if you don't leave it with a single stroke of the brush, almost like rubber glue or Evostick, can make a right mess, being rubbery it doesn't rub down either. £5 for a tiny tin, the last one I had got knocked over by accident...  >:(

I have a Humbrol agent in town, will have a chat with them.  I can always strip the paint and get it anodised in the future when funds improve.  For now I just want it black so I can use it.

I have looked at flocking the inside of the shade and the inside of the cap,  apparently a very simple process but not sure it's a good way forward durability being one concern.  I think the inside of my 16mm fisheye lens cap is coated with flocking, it grips nicely but before making it I would need to know exactly how effectively thick the coating would be, applied manually it may vary. The cap might not go on if it's too tight or might be loose/fall off if too slack, the difference will probably be small between one and the other.

I have looked at the 16mm fisheye cap, it consists of three parts, a tube, a threaded retaining ring and a thin disk, 1.4mm, with the "Nikon" lettering which is retained in the tube by the threaded ring.

I don't really want the complications of making mine in three pieces, screw cutting such fine threads in such delicate pats seems a wast of effort for little gain, however, I will find it very hard to make the disk part as thin as the Nikon one because it may not machine easily, it will tend to bend away from the lathe tool, even with very light cuts, so I am limited how thin I can go by making it in one piece.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: richardHaw on March 06, 2018, 10:52:20
anodization doesnt really cost much  :o :o :o
you just have to contact the correct people  ::)

my friend made tattoo machines and he had his done by a bike parts maker. basically when the bike shop is going to anodize something they will just include his parts with theirs.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 06, 2018, 11:14:47
anodization doesnt really cost much  :o :o :o
you just have to contact the correct people  ::)

my friend made tattoo machines and he had his done by a bike parts maker. basically when the bike shop is going to anodize something they will just include his parts with theirs.

The nearest anodising company to me has a £45 minimum order, which from my description they don't think my pano head parts will cost nearly that much, I feel the pano head would be worth it but I have had a lot of expense recently and have to exercise frugality for a while.

If I do anything which needs galvanising there is a railing company nearby I know the owner and they are happy to send my bits away with theirs, I will ask around, this is an engineering town, the home of British nuclear submarine manufacture.  I would be surprised if nobody sends stuff away for anodising but the key is finding somebody small.  No chance of walking into the shipyard expecting anything except a boot up the backside!  ;D  ::)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 07, 2018, 10:35:44
I have made the lens cap.

The bit of metal which I cut out originally for the hood, (and rejected because there was a drilled hole in the side) has come in for the cap.  It was just big enough and there was just enough thickness to make the cap.

Chucking such a delicate thing in the lathe was something of a challenge but I got there.

This is the lens front with the cap, which still need painting, the 16mm fisheye lens in the background.

(https://farm5.staticflickr.com/4801/25798112517_0f36319f4f_b.jpg)

A self portrait?  ;D

(https://farm5.staticflickr.com/4742/25798113257_72dc6b082d_b.jpg)

...and sharper!  Could have looked happier...  ::)  >:(

(https://farm5.staticflickr.com/4746/26797479508_fa045f9fa4_b.jpg)

Am going to get a piece of black vinyl cut to match the 16mm lens cap with "Nikon" in the middle.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 07, 2018, 17:17:34
Have the Humbrol paint, but left the parts with my local sign shop who are making the vinyl lettering for the front.

While I was getting the paint I enquired if they had any flocking which I could use to coat the inside of the lens cap to help hold it on to the lens hood, in a similar fashion to the 16mm fisheye.  They had, but green, imitation grass for modelling.  I explained what I wanted it for and the lady disappeared for ages, returning eventually with some red coated paper, apparently it's intended to represent red carpet in dolls houses!  Anyway it's 7 thou (0.17mm) thick.  I will need to machine about 8 thousandths of an inch from inside the rim of the lens cap so it will grip the lens hood snugly.  I think I will also put some on the inside face of the cap  too, it will improve the appearance and make it softer on the edges of the lens cap.

A very nice shop... they had brass strips and thin sheet brass, will be back there soon!  ;D
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 07, 2018, 17:18:56
He he Very nice  :D
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 07, 2018, 17:27:19
Sort of fresnel fisheye!  I did think of extracting the circle for an avatar... I just look too mean in that shot.  >:(
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 08, 2018, 21:43:04
Have painted it with an aerosol of black stone chip I happened to have.  Might not work, but if it does it should be robust, I used the Humbrol #33 for inside the hood.

The vinyl looks good on the front of the lens cap, I have used flocked paper for the inside, it's a bit tight to get on and off but it's fine once it's on.  Seems good, the paint needs a second coat.

Probably tomorrow I will final refit the front of the lens.

(https://farm5.staticflickr.com/4781/40654109322_10c30e8c76_b.jpg)

(https://farm5.staticflickr.com/4782/40654109822_1878a6ae66_b.jpg)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 08, 2018, 21:59:26
A very unique Nikkor ;)


I’m sure you will get orders for lens caps for Fish,,, people often loose their caps and on the AF it’s plastic so you have customers I’m sure  :D
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 08, 2018, 22:38:08
Good point Erik, never thought of that.  ::)

Are the hoods on the AF the same as the hoods on the f2.8 MF?  The MF are ~61mm Ø.  I guess thats what the 61K means in front of "Made in Japan" - 61mm cap.

I might just make myself a spare for practice.  Keep the original in the draw.  I am not good with caps, I am always one or two missing, they usually turn up but not always.

I made a leather one for the 80-200 because the hood is screw on and I don't like keep taking it on and off. 
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 09, 2018, 00:10:57
Impetuous is my middle name!  Couldn't wait for the paint to harden, I have fitted the lens front and integral shade to the lens.  I have to say it looks quite handsome, though I say it, I shouldn't.

(https://farm5.staticflickr.com/4778/40698335791_a7d4f4369f_b.jpg)

(https://farm5.staticflickr.com/4798/40698334571_aaf68bde41_b.jpg)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Erik Lund on March 09, 2018, 00:37:01
Here id an old thread with home made lescap for 16mm
http://nikongear.net/revival/index.php/topic,4825.msg88899.html#msg88899 (http://nikongear.net/revival/index.php/topic,4825.msg88899.html#msg88899)


Old One is 64k ;)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Akira on March 09, 2018, 03:04:23
Amazing result...and the lens cap!  Thank you for all the report and congrats!
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Hugh_3170 on March 09, 2018, 04:41:45
Great outcome - well done.

It really looks the part.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Bruno Schroder on March 09, 2018, 08:58:32
Robert, it looks quite handsome :)
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Bent Hjarbo on March 17, 2018, 00:02:08
I am impressed, look awesome.
Interesting to follow your projects, very skillfully made.
Title: Re: AF Nikkor 20mm f2.8 damaged front.
Post by: Seapy on March 17, 2018, 00:12:36
Thank you all, I just enjoy making stuff and fixing things so they work!

Finally got myself an avatar. ::)

11 years since it was taken photographing football (soccer).