Help - Stuck Re-assembling a canon 85 F1.9 Rangefinder

Gatorengineer64 · Joined: 26 Oct 2017 Posts: 283

Tried to do a CLA on this lens, I am still learning. I got the front lens group out, and then barrel, but I cant get the rear lens block out, and I don't see any more grub screws. I also cant get it back together. The barrel threads to the lens block with a multiple start screw thread. I see a black dot on the barell but I don't see any index marks on the threads. Is there a trick to starting these?

How do I get the rear lens block out? It would appear it needs a special tool?

Advice would be appreciated. I did try heating the barrel in hot water, but that didn't help (hoping it would expand a bit).

Question

Gatorengineer64 · Joined: 26 Oct 2017 Posts: 283

calvin83 · Joined: 12 Apr 2009 Posts: 7584 Location: Hong Kong

I think should be able to remove the optical block in one piece?

Take a look at this
https://www.kitamura.jp/photo/repairer/2014/re1063.html

kymarto

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Gatorengineer64 · Joined: 26 Oct 2017 Posts: 283

visualopsins · Expire: 2025-04-11

Tip -- place half on flat surface rather than trying to screw together holding both pieces.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Before taking it apart further, I'd concentrate on finding the correct start, if I was in this situation, I'd get a Sharpie marker and make some marks for the first start I'm going to try, it here's the possibility hard part, some lenses are rather simple to rejoin in that the helicoid doesn't really care about the position of the focus ring, while other lenses it's critical that the focus ring is out towards MFD, possibly half way, at some point the front cell contacts the guide rail(s) that prevent the optics from spinning, it's at this point the guide rail(s) should mate with the intended slot and then the focus ring is turned to draw the helicoid back in, if the lens stops moving inward before the focus ring reaches the infinity mark, or the optics don't reach the desired depth when the infinity mark is reached, these are signs it's the wrong start, which means you have to restart one start earlier or one start later or that the helicoid was in the wrong position when the guide rail mated to the optical block. This is much easier if there is only one guide rail, when there is two rails, there may be two starts that time it right, only that one will have the aperture numbers in the correct position at 12:00 and the other where the aperture numbers are at 6:00 or the bottom, no fear, if it ends at the bottom the correct start is 180 degrees away.

You have to be methodical in how you do this, after your 3rd or 4th attempt you should be forming a picture in your mind of where a start will end up and will be able to predict how far away the correct start is.

Hopefully you can remember if you had to turn the focus ring to unscrew the helicoid for the first part till it cleared the rail, your description leads me to believe you didn't have to do that, so you can probably ignore the part about moving the focus ring to align the rail, but I included it to cover the possibility.

Here's how I witness mark my lens, at the infinity position I will add a single scratch in a hidden spot where an easily identifiable feature on the main body or on the moving helicoid end up at when @ infinity, I usually rotate the focus ring back and fourth a few times as watch how everything moves and where everything ends up @ infinity a suitable marking location usually presents its self.

When separating the helicoid I lightly pull as I slowly turn it, when the helicoid lets go I immediately stop rotating the lens, and immediately rejoin the helicoid and stop with about 1/4" or about 5-7mm overlap and then look for a marking location, I often use the same easily identifiable feature on the body to witness mark the start of the optical block helicoid with a double witness mark

cooltouch · Joined: 15 Jan 2009 Posts: 9096 Location: Houston, Texas

Gator, I've been in your position more times than I care to admit. Even after marking the helical for the correct reassembly point, I've found that this was often of little help and ended up playing the process of elimination game. I did find that, if one of the pieces had a flat side, to lay it on the flat side to make things somewhat easier. Also, I found that, if I held perfectly vertically the part to be threaded onto the part to receive it, that I could feel it fall into place each time the helicals would engage. Then it was just a matter of process of elimination. Not fun, but oh well, what's the alternative?

If you haven't gotten that rear group out yet, you might try using one of those flat rubber "jar gripper" things. I use one whenever I need to unscrew a lens group when it doesn't have any slots for a lens spanner. Usually that'll work.