J-12 LTM: helicoil disassemble, how to ?

maddoc

maddoc

... likes film again.
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I searched here and the www for some information about disassembling the focus helicoil of a J(upiter)-12 in Leica screwmount but could not find anything. There is of course the very good instruction on clean and lube of the J-12 in Kiev/Coontax mount on-line available (which I have) but the mount is completely different from the LTM version.

I am stuck with just the focus helicoil after removing the rear lens-block, front lens-block, and aperture control mechanism (that I was able to disassemble, clean, lube, and assemble). Removing the upper index ring (three set screws) unsheathes a single, very tiny grub-screw on what appears to be the lower index-ring that has to be removed to access a second set screw. However, removing that single tiny grub-screw loosens nothing. So I am stuck and wonder how to get these parts apart to remove the old grease and re-lube the lens.

Thanks in advance for any hint/tip ! :)
 
I've looked everywhere for the LTM J-12 disassembly instructions with no luck. My black J-12 helicoid is so gummed up I inadvertently unscrew the lens while trying to focus.

I'll be watching this thread with great hope and anticipation! :)
 
I think you mean helical or helicoid. Helicoil is a product for repairing stripped threads

;)
 
Lawrence Sheperd said:
I've looked everywhere for the LTM J-12 disassembly instructions with no luck. My black J-12 helicoid is so gummed up I inadvertently unscrew the lens while trying to focus.

I'll be watching this thread with great hope and anticipation! :)
Click to expand...

I am hoping for some hint ...
 
I'm not aware of any resource on the web for this lens and Maizenberg doesn't cover it, as far as I can see. I know that doesn't help directly, sorry. It's not a lens I've had cause to disassemble either. If there's any way to contact Brian Sweeney, it's likely he's had one to bits!
 
Here is google translate from the Russian site Rangfinder.ru
1. Unscrew the rear unit .
2 . Unscrew the front block , mandrel for the apperture.
3 . In the hands of the lens barrel is without optics .
4 . Not to smudge and dust optics , front and rear blocks immediately bolted together without losing the adjustment pads . Close lid and put off to the side.
5 . screw out three radial locking screws on the aluminum frame of a distance scale ( it forward ) . Frame is removed and set aside .
6. screw out only a cog in the second aluminum frame ( with scale DOF) . I pre- made ​​label on the body of the helix against the screw on (just in case ) . Thereafter bezel unscrewed and set aside .
7. In the hands of a helicoid mechanism remains . On the sides of the rear Loosen the two set screws (located in the longitudinal keyway )
8. On the front side of the groove has a short , equal in length to move the diaphragm, and the locking screw on which the power aperture ring within this groove. This also need to unscrew the screw . At this point do not remember , but I can not see already ...)))
But the essence is this: I said risk is completely screwed position helix (corresponding to infinity) and the position of the aperture ring (actually stopper hole ) , and unscrew the helix .
9. Flushing thread helix gasoline and lubrication. I washed out locally , swab with gasoline, ie Do not soak , not flooded .
10 . When assembling the helix most importantly get the right turn ( multiple- thread ) . Achieved experimentally. Very desirable practice on a dry thread ( before greasing ) and visually " noted " the point of call. The main thing is that when fully tightened and risk coincided helicoid , and the hole for the locking screw of the diaphragm was in the right the right range .
11. Well later in the reverse order. Screwed back side locking screws and the front screw aperture ring . Further back aluminum frame is screwed to the end, in principle, we did risk - that's on it. Then fix the rim side cog .
12. Next install the front rim ( distance scales ) to need a place to fix the three screws.
13. Next is screwed optical units . First Front - until it stops, then back. Adjustment ring honey them , which we did not remove ))) .
Click to expand...

here is the original post just in case
1. Открутить задний линзоблок.
2. Открутить передний линзоблок, за оправку диафрагмы.
3. В руках остаётся корпус объектива без оптики.
4. Чтобы не пачкать и не пылить оптику, передний и задний линзоблоки сразу свинчиваю вместе, не потеряв юстировочные прокладки. Закрываем крышками и откладываем в сторону.
5. Отворачиваем три фиксирующих радиальных винтика на алюминиевой оправе шкалы расстояний(она передняя). Оправа снимается и откладывается в сторону.
6. Отворачиваем единственный винтик на второй алюминиевой оправе(со шкалой ГРИП). Предварительно я сделал метку на корпусе геликоида на против этого винтика(на всякий случай). После этого оправа отвинчивается и откладывается в сторону.
7. В руках остаётся механизм геликоида. По бокам задней части отворачиваем два стопорных винта(находятся в продольных пазиках)
8. На передней боковой части есть короткий паз, по длине равный ходу диафрагмы, и стопорный винт, ограничивающий ход кольца диафрагмы в пределах этого паза. Этот винт также нужно вывинтить. С этого места плохо помню, а посмотреть уже не могу...)))
Но суть такая: я отметил риской полностью завинченное положение геликоида(соответствует бесконечности)и положение кольца диафрагмы(точнее отверстия для стопора), и вывинтил геликоид.
9. Промывка бензином резьбы геликоида и смазка. Я промывал локально, тампоном с бензином, т.е. не замачивал, не заливал.
10. При сборке геликоида самое главное попасть в нужный виток(резьба многозаходная). Достигается экспериментально. Очень желательно потренироваться на сухой резьбе(перед смазкой) и визуально "отметить" точку захода. Главное, чтобы при полностью завернутом геликоиде и риска совпала, и отверстие для стопорного винта диафрагмы оказалось в нужном нужном диапазоне.
11. Ну далее в обратном порядке. Завинчиваются задние боковые стопорные винты и передний винт кольца диафрагмы. Далее задняя алюминиевая оправа навинчивается до упора, в принципе мы сделали риску - вот по ней. Потом фиксируем оправу боковым винтиком.
12. Далее устанавливаем переднюю оправу(шкал расстояний) на нужно место, фиксируем тремя винтами.
13. Далее завинчиваем оптические блоки. Сначала передний - до упора, потом задний. Меду ними юстировочные кольца, которые мы и не снимали))).
Click to expand...
 
Ezzie said:
I think you mean helical or helicoid. Helicoil is a product for repairing stripped threads

;)
Click to expand...

you are right of course !

ihorzu said:
Here is google translate from the Russian site Rangfinder.ru


here is the original post just in case
Click to expand...

Thanks a lot for the instructions !! Point #6 in the list is where I am stuck. If "cog" means that small grub screw then after removing that I can`t unscrew anything, the outer, lower ring with the DOF ring can`t be moved at all. This ring also has the M39 LTM mount at this base so I assume the position of this ring with respect to the focus helical is critical to obtain correct back focus.

here is the link to the original topic at rangefinder.ru: http://rangefinder.ru/club/viewtopic.php?t=11047
 
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I found the link to the thread at "The Classic Repair Forum" and via webarchive.org a snapshot of the page where Mike Kovacs (RFF member) described the CLA procedure (without photos, though):

http://web.archive.org/web/20060117...stuff.com/forum/read.php?f=21&i=35746&t=35735

Indeed, to separate the focus helical parts, after removing the distance scale (three grub-screws), the tiny grub screw in the DOF scale part (located above the "Made in USSR") has to be removed and the DOF scaled threaded out. I need to hold the inner helical with a spanner tool to apply enough counter when trying to unscrew the DOF scale.
 
Great info! Thanks to maddoc and ihorzu for the links and translations. I really like this lens on my Canon P (yes, my example fits, but you must mount it carefully) but the lens' wretched focus feel keeps it mostly in its case
 
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