T-mount stuck on lens

Discussion in 'Camera Building, Repairs & Modification' started by polaski, Mar 13, 2007.

  1. polaski

    polaski Member

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    I just acquired a 500mm f/5.6 Century Precision Tele-Athenar lens with a t-mount for SLRs. The mount that is currrently on it is probably a Nikon t-mount. Set screws came out neatly, but the t-mount to flange threads are on VERY solidly. I am hesitant to force it, obviously. Can someone give me suggestions.

    The only thing I can think of it a set of flexible wrap-around wrenches (which would force it and possibly deform one of the ends) and Liquid Wrench (which tends to spead a lot once it gets going. Maybe lighter fluid lightly applied at the join of the thread. I want to be very, very careful about this.
    The base of the lens is pictured. At the end is a Nikon lens cap. Then the T-mount. The longer smooth length above the knurled part of the t-mount is the Century Precision flange that provides the t-mount thread. With the t-mount disassembled, I've got two basic smooth cylinders to unscrew from each other.

    I also am assuming that the t-mount unscrews counterclockwise (that is, normally).
     

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    Last edited by a moderator: Mar 13, 2007
  2. richard ide

    richard ide Member

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    Before doing anything else: try 2 wide rubber bands. It is amazing how much torque you get when the parts don't slip.
     
  3. Roger Hicks

    Roger Hicks Member

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    Or indeed household rubber gloves.

    Cheers,

    R.
     
  4. Dan Fromm

    Dan Fromm Member

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    Jeff, Century delivered those lenses in Century mount. This is sort of a super T-mount, with a larger thread and longer back focus. They also sold adapters to other mount systems including T. When I had my 500/5.6 TA II rebuilt by Century I bought a T-mount adapter for it so that I could use it on any old SLR.

    If there's just one adapter on yours it probably is a Century-to-Nikon F.

    If I were you I'd call Century, now owned by Schneider, for advice. www.schneideroptics.com.

    And if I had known better I'd not have bought mine or, having bought it, sunk so much money into a rebuild. After it was all good as new I got a tripod mount adapter from SRB for it -- more expense, but much less expensive than Century's own -- and shot with it. The lens is an achromatic doublet at the front of a long tube, not a telephoto lens, and it suffers from chromatic aberration, which manifests as color fringing.

    Good luck, have fun,

    Dan
     
  5. copake_ham

    copake_ham Inactive

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    Just to note,the Nikon mount is a "F mount" not a "T mount".
     
  6. polaski

    polaski Member

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    OK, It came apart

    Based on many people's advice, I methodically took the t-mount apart. A total of 9 (count 'em, 9) set screws, and when they were loosened, the parts of the t-mount sort of slid apart. The Century Precision t-mount adapter flange (receiver) came off the lens, and then I had total freedom to work with two steel cylinders completely detached from any optics or mechanisms.

    Ronsonol lighter fluid (Que-tip applied) soak came first. Then the rubber gloves (Thanks, Roger, they were in the camera toolkit, but I always regarded them as skin protection). Then Liquid Wrench. The again and again until bedtime came and I soaked the joint in Liquid Wrench overnight. This morning, the joint unscrewed.

    Dan, as I understand, the Tele-Athenars were doublets, the Tele-Athenar II lenses were triplets (as if I understand the optics). You're right about the Nikon mount -- that's what the seller had used the lens on. I had been in touch with CP, and a very fine fellow who owns some of these lenses sent me scans of a full set of specs on the range of Tele-Athenars that were T-adaptable.