FD Lens Bushing Repair - Here's a How To for the Canon FD 24mm f2.8

Started Feb 3, 2016 | Discussions thread
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bolesautomotive
bolesautomotive Forum Member • Posts: 99
FD Lens Bushing Repair - Here's a How To for the Canon FD 24mm f2.8
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A few days ago I asked for help locating the microfiche or parts list for this lens. No response from the community led me to think either no one cares (likely do to age of lens) or no one could provide a suitable answer. So, I came up with a solution. I hope this helps someone in the future.

Images are not for beauty so don't expect much. Also, the lens being repaired has been well loved and obviously seen many days loose in a bag.

If your FD lens flops around inside the barrel or if the lens moves forward and backward freely you may have worn bushings. This lens had worn bushings that allowed the rear lens group to move in and out by 2mm making focusing a pain.

Here's how I fixed mine. If you attempt this do so at your own risk. This is to help those who wish to try this on their own. Myself and this website cannot be held responsible if your lens suffers in any way from an attempt by anyone to do what I have done here.

Here we go

Front of the lens.

To start the plastic lens ring with CANON LENS FD 24mm 1:2.8 is removed by unscrewing it counter clockwise. This can be achieved using a large rubber o-ring pressed against the plastic and turned counter clockwise. I didn't take a picture of the o-ring but it needs to be thick enough to extend beyond the barrel. If you can't do it by hand just push the lens face down onto a table with the o-ring between the lens and the table and unscrew the lens from the o-ring. I acquired the o-ring from a kit I use at my automotive shop. They are less than $1 USD at the auto parts store.

Plastic Ring Removed

Now with the plastic name plate ring removed you can see these six phillips screws. Removing three of these will allow for the lens filter ring to be removed. The other three will allow the front lens group to be removed. Once you remove all six of these screws be prepared for the front element group to fall out. Don't drop it!

Front Lens Group Removed

With the front lens group removed you can now see the inner lens group. The inner lens group and rear lens group are attached together. They are both attached to the inner black barrel you see here. At this point you will want to mark the orientation of the parts you can see here. Set the lens to infinity focus and make a scratch mark across the two inner barrels and inside the outer barrel. This is crucial. If you do not mark the orientation of the barrels you will be in for a long frustrating night trying to clock the lens properly. This lens must be timed in order to work properly. Don't let this deter you, just be sure to take plenty of pictures and always work from either infinity focus or the lock past 0.3 m.

Rear View with Lock Ring and Rear Cover Removed

The rear mounting ring (silver) can be removed by removing the three black screws on the outside of the barrel that hold the ring to the barrel. The first screw is next to the lens mount release button. WARNING - These little guys are often in with thread locker. It is ESSENTIAL that you use a quality screw driver of the proper size. Using a cheap screw driver or the wrong size will strip the screw heads which will then need to be drilled out (not fun).

In this picture the rear cover has also been removed. The rear cover holds the lock level and aperture level. Once the mount ring has been removed the rear cover can be lifted from the lens. You will hear the aperture lever in the lens click as it moves to a resting state. No worries this is not a problem.

You now see the three screws which are visible in this picture. These three screws hold the mounting ring release button barrel to the lens. Remove the three screws you see in this picture and lift the release button barrel. Beneath is the aperture control ring.

Aperture Ring Removal

Now you see the aperture control ring. Turn the aperture to f2.8 and lift the ring up. There are no screws here to remove. Immediately turn the aperture control ring over and make sure the steel dowel has not fallen from the ring. There is a very small dowel approximately 2mm by 1mm in this ring. This dowel is what provides resistance and makes the clicks you feel when changing the aperture. Without it you will not be able to lock the aperture in any single location. TIP - Once the aperture control ring is removed and you see that the aperture dowel is still in place dab a small amount of grease on it to keep it from growing legs while you continue to work on the lens.

The two tabs sticking up next to the rear lens group are the aperture lever and lock lever. You can play with these to see how they function. It will be a good idea to familiarize yourself with how they operate so assembly will go smoothly later on.

Aperture Control Ring Removed

Now you can see the two stays secured by four phillips screws. These stays are basically guides. They keep the inner barrel from rotating with the middle barrel. This is why it is crucial to mark the barrel before disassembly. They must be clocked correctly or the lens will not function properly.

AFTER MARKING THE BARRELS remove the four screws. Once these four screws are removed the middle barrel, inner barrel and lens group can be removed as an assembly from the focusing barrel (outer barrel). Once again, I can't stress the importance of marking the barrels not only to line up but also for depth when lined up.

Don't twist this assembly out yet.

Rubber Removal

To remove the rubber grip from the focus barrel just slip it over the front of the barre. Simple as that!

Outer Barrel Seperation

The outer barrel separates into two halves. The separation point is beneath the grip. Just pull it apart. There are no screws or secret tricks here, just a good hold and strong pull will separate the two halves.

Middle barrel, inner barrel, lens group and bushings.

Here we have removed the middle barrel, inner barrel and lens group from the outer barrel. If your lens had smooth focusing youwill not need to remove this completely from the outer barrel (and I strongly suggest not removing it unless completely necessary).

With this removed we can see holes in the aluminum barrel. One is notched while the others are simply circular holes. The notched hole is the one that allows removal of the bushings. In this picture you can see the three brass bushings lying to the left of the barrels.

If you do not need to remove the aluminum barrel from the outer barrel then only rotate it outward enough to see the square window in the aluminum barrel. Once you can see clearly into the square window then rotate the inner barrel until a screw becomes visible within the window. Remove the screw and bushing then rotate the lens until the next screw is visible in the window. There will be three of these screws/bushings. Remove them through the window. Be Careful - when you remove the last screw the inner lens group will slide out Hopefully you marked the orientation of this group so you can put it back together correctly. Make sure you mark where the first screw was removed from and which way you turned he inner barrel to access the following screws. If you don't you will not have correct infinity focus or possibly will not be able to reassembly the lens properly.

If you did remove the middle barrel and inner barrel you can clean them. I used white lithium grease in very small amounts to lubricate the threads of each barrel. You will find much more grease in the lens than is actually needed to function properly. The old grease will be grey due to metal particulates that have been captured in the grease. It used to be nearly clear!

Heat Shrink Tubing used to increase bushings thickness

My first attempt I used black heat shrink tubing to add thickness to the bushings. The problem I ran into was that grease saturation of the heat shrink caused it to deteriorate and lose shape. This caused the focus ring to become difficult to rotate. This is simply to show the process I went through. Do NOT use regular black heat shrink tubing.

Heat Shrink as a bushing sleeve.

This is what the heat shrink tubing looked like when used as a bushing sleeve. During installation the sleeve wanted to slide off the bushing further making this less useful for this repair.

Plastic Heat Shrink Tubing Works Best!

Here plastic heat shrink tubing was used. The bushing is installed only two show it on the inner lens group. I cut approximately 3mm long tubes from this heat shrink sleeve. I held the bushings with a dentist pick a allowed the heat shrink tubing to hang around the brass bushing. I heated the shrink with a lighter until it formed tightly to the bushing.

NEXT - The bushing will need to be sanded to fit into the square opening on the aluminum barrel just as the bushings were removed. Sand the heat shrink to make a square that fits easily into the aluminum barrel. I did this with an old nail file. Do not sand into the bushings. This will cause additional play in the bushings and will require they be replaced.

If you did not remove the middle and inner barrel from the outer barrel you can now fit the bushings into the square window. Apply a small drop of lubricant to each bushing once it's been installed to the barrel.

Assemble in reverse direction and enjoy your lens! Mine is rock solid now.

AGAIN - I cannot stress how IMPORTANT it is that you mark the orientation of each piece. If not you will have to reverse engineer how the focusing mechanics works and how to clock it properly. Even if you get it to line up properly you may find the aperture does not function properly or focus is not correct. I have made this mistake on several lenses while being in a rush and all I can say is if this happens, breathe, be patient and take breaks.

Hope this helps! Have a great day!

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