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Christi_l
Tinkerer
Username: Christi_l
Post Number: 2
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 26, 2010 - 03:07 pm: | 
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So sorry, not a breech mount as I stated in earlier thread. It is the Canon fd bayonet mount. I have an canon FD 400mm. I was shooting the other day and one of the tripod legs gave way. It fell to the ground and the camera attached took the blunt force. The camera is broke and in very bad shape. After looking at the lens the only damage is to the chrome metal ring bayonet lock. It bent as the camera separated from it. The dust cap will not go on smooth and so the metal ring will need to be replaced. I am asking for your help in letting me know if this is major or minor and how you would recommend me to proceed. All your help is greatly appreciated... Thank you... |
Christi_l
Tinkerer
Username: Christi_l
Post Number: 3
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 27, 2010 - 10:02 am: |
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Here is a photo of the problem I described. Thanks so much for any help... |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 12
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 27, 2010 - 09:18 pm: |
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You should replace the part if possible. Part number for the tightening ring on the 400mm 2.8 L is CF2-0330. Most FD lenses have this part held on with three screws on the side of the lens so not a bit deal to replace. The tightening ring on other FD lenses, although similar looking, is not the same part number as for the 400mm. |
Glenn
Tinkerer
Username: Glenn
Post Number: 836
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 10:23 am: |
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L Series spares are like hens teeth in this day and age, but I have repaired bayonet rings that have been far more badly deformed than the example illustrated. Any skilled metal worker will have it back in proper shape in no time. You should note that the securing screws are torqued up very tight by the factory and have JIS head forms - use the correct, properly fitting screwdriver otherwise you will bugger up the heads and have to drill the sods out - be warned!
Remove the bayonet ring and then turn up a steel former that is a good push fit on the rings inner diameter. Using a brass dolly and a light hammer, gently work the 'lugs' back into proper shape and position. Because the metal will have stretched somewhat, you may have to carefully file up the inside edge and curved ends of the lugs in order that the lens fits the camera mount smoothly. Do not try and just hammer the ring back into shape - if the former is not used the ring will distort and you will never get it to fit again. |
Glenn
Tinkerer
Username: Glenn
Post Number: 838
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 02:08 pm: |
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I have just looked at the Canon parts and repair microfiches - The bayonet ring or 'Tightening Ring' as Canon calls it, part nos CF2-0330-000 is not unique to the 400mm f2.8. It is fitted to the following lenses:-
nFD 300mm/f4 held by 3 radial screws
nFD 300mm/f4L held by 3 radial screws
nFD 400mm/f2.8L held by 6 radial screws
nFD 400mm/f4.5 held by 6 radial screws
nFD 500mm/f4.5L held by 6 radial screws
Canon's logic here seemingly is that the heavier lenses needed more than the standard 3 tiny screws, found on the lesser focal length nFD lenses because the people using these lenses always tended to use motordrives also. This obviously makes the camera body much heavier, so the CF2-0330 ring is drilled for six screws, where as the normal CF2-0111-01 ring is only drilled for 3 screws. It is also possible that a better spec material was used for the ring fitted to the heavier lenses.
Now I have no idea if the 0330 and 0111 rings are interchangeable fit wise, certainly the screw holes drilled at 60 deg spacing will allow 3 screw fixing rings to be retained in the 400mm lens if all else is equal. Unfortunately I do not have a 400mm f2.8L to experiment on, mine was ditched years ago as soon as autofocus became reliable, but I cannot see why a ordinary ring from a shorter length lens should not work temporarily if its dimensions are the same and you refrain from hanging a motordrive on the body.
As anyone who has used one of these lenses will state, you do not hang a lens weighing nearly 6kg from the camera body - The lens is supported on a STRONG/SECURE tripod and the camera 'hung' from the lens unit. Thus if you take care a 3 screw fixing should make a good temporary repair, assuming a 3 hole ring will fit in your lens's rear mount.
I suggest that you look very carefully at one of your standard lenses and compare the rings and if they look similar buy a gash 50mm/f1.8 and try fitting the ring in your lens. If it fits properly you could even drill and tap out the extra screw holes. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 14
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 04:08 pm: |
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Well, the idea of using a tightening ring from another lens, say a common 50mm sounds good but I would not recommend it. For one thing, the tightening ring on the 400mm is held on with six screws instead of only 3 on the 50mm lens and they do not line up at all so you would have to drill and tap six new holes in the tightening ring. Also, the tightening ring on the 400mm is made a bit thicker to hold the weight of the 400mm (weight of the 400mm tightening ring is 7.4 grams, the weight of the 50mm ring is 7.2 grams)If you want to replace your ring with the correct part, please PM me as I have many brand new original Canon parts available including the CF2-0330 ring that you need.
Bill |
Glenn
Tinkerer
Username: Glenn
Post Number: 839
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 28, 2010 - 06:50 pm: |
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Christi,
Take the man up on his offer of the supply of a new part - I think you will find that it is only the well established independent repairer that has stocks of FD spares and these people are getting thin on the ground nowadays. |
