View Poll Results: What lens cap sizes do you want?

Voters
11. You may not vote on this poll
  • 32mm

    1 9.09%
  • 35mm

    0 0%
  • 40.5mm

    0 0%
  • 42mm

    0 0%
  • 46mm

    1 9.09%
  • 48mm

    0 0%
  • 50mm

    0 0%
  • 52mm

    3 27.27%
  • 58mm

    3 27.27%
  • 62mm

    3 27.27%
  • 67mm

    5 45.45%
  • 70mm

    5 45.45%
  • 80mm

    3 27.27%
  • 95mm

    0 0%
  • 105mm

    1 9.09%
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Thread: Acetal Lens Caps

  1. #21

    Join Date
    Jan 2006
    Location
    Tucson AZ
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    1,298

    Re: Acetal Lens Caps

    More than you probably wanted to know but

    Acetal is the common name for a family of thermoplastics with the chemical name "PolyOxy-Methylene". Acetal is available in a general purpose
    copolymer grade, a homopolymer version (Delrin ), and several filled grades. Acetal provides high strength and stiffness, enhanced dimensional
    stability, and is easy to machine. As a semi-crystalline material, acetal is characterized by a low coefficient of friction and good wear, high strength,
    stiffness, dimensional stability, very low moisture absorption, good wear and abrasion resistance and a wide range chemical resistance.


    Delrin is a Dupont version of Acetal with slightly different properties. Japanese companies love Delrin/Acetal and we used it for some extremely high precision gear trains. BUT our US customer made us use a different plastic and/or or limit the total amount per unit to XX grams or less because of its flammability. Its easy to machine, stable, low friction. All good. But the "flame and smoke" compliance guys for electrical equipment don't like it. It's not going to burst into flames on your lens or in your pocket, but in a fire large quantities can cause problems.

  2. #22
    Jac@stafford.net's Avatar
    Join Date
    Dec 2012
    Location
    Winona, Minnesota
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    4,118

    Re: Acetal Lens Caps

    Does Acetal out-gas?

  3. #23

    Join Date
    Sep 1998
    Posts
    10,357

    Re: Acetal Lens Caps

    Quote Originally Posted by Jac@stafford.net View Post
    Does Acetal out-gas?
    You mean if it is not burning? To be approved for flight on the Space Shuttle NASA burned a Linhof Aero Technika and a Rollei 6008. To qualify the type of internal wires on the Linhof had to be changed because the original wires would out gas in a fire. On the 6008 we had to stop using a silicon filled fuse in the battery as they didn't want to have little pieces of silicon sand free floating if they broke a fuse.

  4. #24

    Join Date
    Feb 2001
    Location
    Shodoshima, Japan
    Posts
    838

    Re: Acetal Lens Caps

    Jim, thanks for the detailed description. I read up on the different kinds of POM and those are exactly the reasons for choosing it.

    Jac, no, acetal does not out-gas. Your lenses (and mine) will be safe.

    Kumar

  5. #25
    Jac@stafford.net's Avatar
    Join Date
    Dec 2012
    Location
    Winona, Minnesota
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    4,118

    Re: Acetal Lens Caps

    Bob Salomon you are the fountain of information. Thanks for that.
    .

  6. #26
    Peter De Smidt's Avatar
    Join Date
    Jan 2001
    Location
    Fond du Lac, WI, USA
    Posts
    5,375

    Re: Acetal Lens Caps

    Sorry for the delay. Here's my wish list:

    1 - 48mm
    1 - 51mm
    1 - 72mm
    4 - 85mm
    2 - 87mm
    2 - 118mm
    "Why can't we all just get along?" President Dale, Mars Attacks

  7. #27

    Join Date
    Feb 2001
    Location
    Shodoshima, Japan
    Posts
    838

    Re: Acetal Lens Caps

    I've compiled a list of lens cap sizes for Fuji lenses. I'll be making similar lists for Rodenstock, Schneider and Nikkor lenses, as well as older lenses - Zeiss, Voigtlander, etc. This is certainly not complete, and I'd be glad to have more data for other lenses. Just let me know here, and I'll add them to the chart.

    10 days after I posted this on various forums, the order of preference according to the polls and messages I've received is:

    1. 70mm - Most Fuji lenses use that size for the front cap.
    2. 80mm - Almost all of them are for Mamiya RB / RZ lenses. The general complaint is that the spring on one side breaks, rendering the cap unusable.
    3. 48mm - Mainly for the older Fuji lenses
    4. 67mm
    5. 62mm
    6. 58mm
    7. 52mm

    Also, I think most users seem to have asked for front caps only! LF lenses need rear caps as well, and in many cases, the rear element is relatively less well-protected. Sometimes the element is almost flush with the barrel.

    The manufacturer is sending me the final samples soon, and I will share photos here. In the meanwhile, please go through the list. If there are any errors, please let me know, and I would appreciate your input on other lenses.

    Thanks,
    Kumar
    Attached Files Attached Files

  8. #28

    Re: Acetal Lens Caps

    Kumar, have you made any provision for those lenses where the center of the front element (stupidly!) protrudes past the filter ring? This would require a step inside to sit on the filter ring and keep the face of the cap above the lens.

  9. #29

    Join Date
    Feb 2001
    Location
    Shodoshima, Japan
    Posts
    838

    Re: Acetal Lens Caps

    Yes, I have thought about it, and will make those kinds of caps as well. Unfortunately, I do not have any of those lenses in my collection. If members could contribute to this thread, listing such lenses and their outer diameter, I will start getting drawings and samples made.

    Final samples of the 48mm size caps should be here by towards the end of the month.

    Kumar

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