Canon FD50 breechlock extension tube stuck on 100mm f4 FD breechlock Macro

[binglebugbob]

I've had and used Canon FD stuff for years and never run into this problem: I bought a clean 100mm f4 Macro (breechlock) lens. It came with the FD50 extension tube ("lifesize adapter"). I put it away for a couple of weeks and decided to remove the FD50 from the lens.

I can't budge the breechlock ring on the lens. The breechlock ring on the tube seems to work OK. I've tried about everything I can think of with no success. Anyone run into this problem or have an idea as to how to remove the extension tube? I guess if all else fails, I can start disassembling the extension tube, but I'm hoping that isn't necessary..

Thanks for any assistance!

Bob.

 

[AgX]

I got the same problem with a 2nd-hand kit that I bought with the New-FD lens stuck onto the body. I had to disassemble the mount of the lens to get the lens off the body.
In my case the reason was a tiny grain of sand. To me the brechlock version seems less prone to this. But nevertheless in your case I would take off the brechlock ring to get things moving again.

EDIT:

And the only way to do so would be to cut-off the flange of the breechlock ring. Thus this should be only the last resort.

Alternative way would be heating just the ring to make it expand a little.
Or brute force. The only things to be damaged would be that ring and its male counterpart. Both are easily to be replaced if necessary

 

[shutterfinger]

I would put some penetrating oil on the mating surfaces and allow to sit for a few hours with the lens side up then give it another try.
Soft heat method (no oil), heat oven to 150°F to no more than 200°F, turn off when the temperature is reached, place the stuck assembly on the center rack, close the oven door and allow to sit for 15 to 20 minutes. Try to disassemble while warm.

 

[AgX]

Placing the lens front-lens-up would not allow the lubricant to reach the mated flange surfaces. After dripping it into the slit between the flanges one must at least for a short time put the lens upside-down.

 

[MartinCrabtree]

Set it in the window with bright sunlight for an afternoon and attempt disassembly while hot.

 

[binglebugbob]

I'll give it a shot. I tried lighter fluid with no luck.

Heat may work, but it feels awfully solid. Setting it in a window is probably the safest way to heat it. I'll try that first.

 

[AgX]

Lighter fluid would run where it wants. Nor is there a reason to use it. The grease used for the ring is not known for hardening and at the flanges themselves would not be grease, and if then it should not form annoying resistance.

Before doing such attempts one should consider what likely is the reason for the fault.

I do not see the point behind placing the set in a window. Though of course it is the most harmless attempt of repair one could do.

 

[MartinCrabtree]

Expansion often allows enough room to disassemble a device that's stuck. And long term gentle sunlight on an object is the easiest way of not overdoing the heat. I've had that method work many times. It requires patience which is needed with precision assemblies.

 

[John Koehrer]

I'd opt for a vacuum cleaner belt around the locking ring. Or try wearing gloves. Or a strap wrench. Or a rubber jar opener Or, or. or........>

 

[AgX]

What is a vacuum cleaner belt?

A rubberized carrying belt? Our vacuum cleaners have no belts...

 

[binglebugbob]

One of these techniques may work, but this feels more like something mechanical is out of place. I hope it can be turned with more force, a better grip, or heat, but it feels solidly and mechanically locked...not just sticky.

 

[shutterfinger]

What is a vacuum cleaner belt?

http://hoover.com/parts/category/be... belt&ef_id=VljY2wAAAEvK9qQV:20160107004929:s belts are under the Parts tab
Upright vacuums that have a rotary brush or are self propelled use flat rubber belts for the drive off the main motor.

 

[shutterfinger]

Well going the lighter fluid and sunlight route I'm betting you get a hack saw and cut it at the mating seam.
Maybe a Dremel with a cutoff wheel.

I have the original version, these may be an improvement. http://www.sears.com/craftsman-2-pi...sellerId=SEARS&prdNo=1&blockNo=1&blockType=G1

 

[randyB]

Careful use of a strap wrench would be my first attempt. 2nd attempt would be to wrap the lens in several ziplock bags and put in the freezer for an hour to shrink the metal, then try the strap wrench again. I would NEVER cut/grind anything, why destroy your lens.

 

[shutterfinger]

Metal working 101: cold metal can crack or break easily, warmed metal is soft and flexible.

 

[randyB]

freezer

Metal working 101: cold metal can crack or break easily, warmed metal is soft and flexible.

My experience has been that 1 hour or so in a home freezer will not cause the metal to crack. You have to go much colder than 0 degrees.

 

[shutterfinger]

Heat is used in many industries to free stuck metal components as is penetrating oil. Heat is faster than freezing. The reason heat or freezing works is the expansion of the metals during heating and contraction during cool down breaks the bond between the two materials. With freezing its the contraction during cool down and the expansion during warm up. The heat method in post #3 is faster and safe.
Penetrating oil breaks the bond by chemical action.

My experience has been that 1 hour or so in a home freezer will not cause the metal to crack. You have to go much colder than 0 degrees.

Changing the metal shape while cold may cause a crack while it is less likely to crack when warm with the same amount of movement applied in either condition.

Perhaps Binglebugbob will let us know when he has succeed in separating the stuck lens and extension tube. I suspect corrosion but it may be a loose mount ring screw or a slight bend in the flange on the tube or lens.

 

[Fixcinater]

Is there any sign of damage on the outside of the macro tube or lens? Maybe they were dropped together, hence distorting the flange as Shutterfinger mentions.

 

[AgX]

That would not alter the difficulties in getting the two pieces apart.
The way the FD mount is designed it is hard to imagine that a knock on this lens/tube combo could have damaged the mount.

 

[binglebugbob]

I suspect it could be a loose screw in the breechlock ring. If there weren't cemented glass elements involved, I wouldn't be concerned about applying heat or cold, but I'm concerned that excessive temperature extremes could cause the cement between the elements to fail and lead to separation.

Someone with more experience than I have has offed to take a look at it, and I'm going to send it to him. If this were a cheap kit lens, I wouldn't hesitate to experiment with it, but I'd prefer not to mess it up. I'll let you know what happens.

Thanks for all of your suggestions. Especially the vaccuum cleaner belt. hadn't thought of that one. (Always wondered what vaccuum cleaners used to hold their pants up. sorry. )

 

[AgX]

There are likely indeed 3 screws that attach the mount assembly to the barrel. And a loose screw could block the breechlock ring. But that the screw would be in such a location to block the ring without any movement is not likely.
And it would necessitate to cut the ring as described.

Keep us informed how things evolved. Maybe it still was something none of us thought of...

 

[shutterfinger]

According to SK Grimes web site Canadian Balsam needs to be heated to 300°F to separate. http://www.skgrimes.com/library/old-news/old-lenses-can-be-restored-by-re-cementing The cement used in your lens is less affected by heat.
I had a Dagor that was fairly cloudy. I put it in an oven at 225°F for half an hour, sat it in boiling water, and it would not separate. I sat it aside and did not look at it for a few months then when I did it had cleared.

Soft heat in an oven will not harm lens unless they have rubber or plastic barrels. Direct heat such as an open flame or electric heating element can damage the housing. If lens were damaged by 200°F-250°F temperature then you could not use them in direct sunlight on hot days.

 

[binglebugbob]

It turns out that someone (the incredible hulk?) had twisted the lock ring too tight. Someone here who had a strap wrench graciously broke it loose. So I bought a set of them myself. It's a cheap but handy tool.
bob.

 

[MartinCrabtree]

Glad to hear you got it sorted out.

 

[shutterfinger]

I was in the Air Force in the early 1970's. I worked on an aluminum airframe aircraft. I was observed installing a component without using a torque wrench to tighten the bolts by quality control. Once I signed off the forms as the installation complete QC did an inspection of the installation to include using a torque wrench to test the torque on the bolts. There was a 10 inch pound either side of specified torque tolerance, the bolts were the specified torque ± 1/2 inch pound. QC and the shop chief were amazed. I told them I had calibrated my arms. Good to hear you got it fixed without damage.