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Canon 50mm f1.4 ltm disassembly
Old 05-15-2011   #1
SteveM
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Canon 50mm f1.4 ltm disassembly

I've found and followed some instructions for cleaning the Canon 50mm f1.4 ltm lens, and initial disassembly is quite easy. However, the main part I want to clean and re-lube is the focus helical.

Once the rear retaining ring is removed, the focus assembly slides off the back, leaving the lens group intact. Next, I removed the small screws holding the rear portion from the focus barrel. The remaining part contains the focus helical - see the attached photos. The first photo shows the threads of the helical protruding at their maximum. All screws have been removed, including the two little screws visible from the back of the lens.

From this point, and I can't see how to undo the inner from outer helical to clean and re-lube. Can anyone advise on how to do this?

Thanks,

Steve
Attached Images
File Type: jpg Canon_50mm_1.4_front_focus_helical.jpg (78.6 KB, 129 views)
File Type: jpg Canon_50mm_1.4_rear_helical.jpg (74.5 KB, 111 views)
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Old 05-15-2011   #2
johnamazement
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I cleaned a f1.8 version a little while ago and if it's the same (and I remember correctly), look down from the front and you should see a two blocks 180 apart from one another. One of them has a sort of tongue which points down towards the mount. This acts as a stop to the helical's movement. When removed (you should see a screw on top) the helical can be screwed all the way out giving access to the full length of the thread.
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Old 05-15-2011   #3
SteveM
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John, thanks for the info. The 1.8 helical seems to be held in place a little differently than the 1.4. However, using the theory that if you stare at something long enough you begin to see things you didn't notice, I've now got it apart. No screws hold the helical together, it is another retaining ring. I've attached a few photos to show this.

The first photo shows the rear mount (you can see the infinity lock stop), the helical itself, and the retaining ring. The ring is difficult to see at first (at least for me) but can be removed with narrow width lens spanner. The focus helical then can be unscrewed to relube.

The second photo shows the focus ring at the back, the focus helical to the right and the helical retainer in front. In the retainer, you can just see a small tab at the top. This is held in place by two small screws that can be seen on the rear mount of the lens, and they don't need to be removed. This tab fits in the groove that can be seen in the focus helical to stop it rotating as the lens is focussed.

I've been playing around with some vacuum grease and can't get the right weight on the focus damping, but I've read that white lithium grease works well. I'll be giving that a try next.

A final note, the lens group does not need to be touched if you only need to relube the focus helical. Once the back end of the lens is off, you also have access to the aperture indent bearing, but so far I haven't dug in deeper to relube the aperture ring. It looks like the front of the lens needs to come off. Maybe later. This is one solidly made lens.

Steve
Attached Images
File Type: jpg Focus helical group 1.jpg (75.9 KB, 152 views)
File Type: jpg Focus helical group 2.jpg (95.1 KB, 125 views)
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Old 05-17-2011   #4
pbo
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Hey Steve,

I'm trying to take off that hard to see retaining ring to relube the lens, but I've been trying for about 20 minutes now, and it doesn't come off! Is it screwed in very tight? I'm rotating counter-clockwise.

Bo
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Old 05-17-2011   #5
SteveM
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Quote:
Originally Posted by pbo View Post
Hey Steve,

I'm trying to take off that hard to see retaining ring to relube the lens, but I've been trying for about 20 minutes now, and it doesn't come off! Is it screwed in very tight? I'm rotating counter-clockwise.

Bo
It was relatively tight on mine, and it was not easy to get the wrench tips into the slots of the retaining ring. I pushed the tips in at the same time as rotating, holding ring in one hand, wrench in the other. Once it had moved a tiny bit, it rotated very easily. Counter-clockwise rotation is correct.

Steve
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Old 05-17-2011   #6
SteveM
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Oh, one more thing that might help. The helical on my lens were pretty tight so before I took it apart I dabbed small amounts of naptha into the threads. With a bit of working around this loosened the threads a lot. Try dabbing a bit of naptha into the space between the outer chrome rear mount of the lens and the brass retaining ring - that's where the threads engage.

Steve
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Old 05-17-2011   #7
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Quote:
Originally Posted by SteveM View Post
Oh, one more thing that might help. The helical on my lens were pretty tight so before I took it apart I dabbed small amounts of naptha into the threads. With a bit of working around this loosened the threads a lot. Try dabbing a bit of naptha into the space between the outer chrome rear mount of the lens and the brass retaining ring - that's where the threads engage.

Steve
Thanks, I was using GooGone and it's still not turning. I'll try some more I guess. I'm thinking about putting the whole focusing part into a ziplock and putting it into a fridge or under running hot water, see if the different metal parts (chrome and brass) expand/shrink at a different rate.
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Canon LTM 50mm 1.4 Pro Repairs
Old 03-21-2014   #8
High Life Kojo
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Canon LTM 50mm 1.4 Pro Repairs

I bought a Canon LTM 50MM 1.4 lens which is in excellent shape but is very stiff at the f stop ring. I does not move easily and I wonder is a pro repairer could be recommended to take a look at it.

Thanks,

High Life Kojo
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Old 4 Weeks Ago   #9
richowirawan
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Hi Steve,

Do you know where to look at the disassembly manual for this lens? I tried to look for it online but couldn't find any trace.
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