J-12 LTM: helicoil disassemble, how to ?

[maddoc]

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 ! 🙂

 

[jarski]

this probably helps you forward.

 

[maddoc]

this probably helps you forward.

Thanks for the link but that is the one instruction I know and have. Unfortunately, the LTM mount/helicoil part is completely different ... 🙁

 

[Lawrence Sheperd]

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! 🙂

 

[Ezzie]

I think you mean helical or helicoid. Helicoil is a product for repairing stripped threads

😉

 

[maddoc]

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 am hoping for some hint ...

 

[wolves3012]

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!

 

[ihorzu]

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 ))) .

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))).

 

[maddoc]

I think you mean helical or helicoid. Helicoil is a product for repairing stripped threads

😉

you are right of course !

Here is google translate from the Russian site Rangfinder.ru


here is the original post just in case

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

 

[maddoc]

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.

 

[Lawrence Sheperd]

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