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Odd size on anchor chain?

Discussion in 'Ask All Sailors' started by SFS, Jan 1, 2017. Add this thread to a FAQ

  1. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    OK, here is today's puzzle. I measured my anchor chain today with my calipers, in preparation for ordering a Mantus swivel. Caliper read 0.338 inches. Not a decimal equivalent of a fraction I could think of immediately, so I measured another link, and got 0.337 inches. Measured a third link, and got 0.338. I love the precision, but I'm stumped.

    3/8" would be 0.375", 5/16" would be 0.3125", 11/32" would be 0.3437". What gives? Am I measuring incorrectly? I put the calipers on the diameter of long straight side section of a link. The chain is not rusted, and the galvanizing is in good shape and seems very uniformly distributed.

    Or did the PO buy 8.6 mm chain?
     


  2. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    Just found an online website that lists their 5/16" as nominally 0.330" diameter. Maybe this is 5/16" (regardless of the math).
     


  3. dlochner

    dlochner

    Joined Jan 11, 2014
    487 posts, 68 likes
    Sabre 362
    US Oswego, NY


  4. Charles Erwin

    Charles Erwin

    Joined Jan 30, 2012
    747 posts, 35 likes
    Nor'Sea 27 - "Kiwanda"
    US Portland/Olympia
    Look at a link and see whether it is marked A4, G4, B3, something else, or maybe not marked at all. Then find the table that matches the embossed mark. My notes say G4 or A4 is .330" but designated 5/16 11.7 links per foot. 3B is .343 and likewise designated 5/16" 12 links per foot.

    Pretty sure the embossing is on 5/16 and up 3B and every size of G4. ACCO has the tables in its catalog at http://www.newmorning.info/page65/files/Acco Chain Catalog.pdf

    For what it is worth - measured a lot of chain - I never had one case that was a dead match to the table.

    Charles
     


    Last edited: Jan 1, 2017
  5. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    Charles, you are my new hero for that last comment. And next time on the boat, I will see how many links per foot it is, and look for the embossing mark.
     


    Last edited: Jan 1, 2017
  6. Ron20324

    Ron20324

    Joined Jan 22, 2008
    4,878 posts, 211 likes
    Beneteau 323
    US Annapolis MD
    and don't forget the metric sizes.>
     


  7. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    ^ Uh, I considered that in the OP...
     


  8. BudGates

    BudGates

    Joined Apr 19, 2012
    897 posts, 76 likes
    Macgregor 26d
    US Ridgecrest CA
    .336" = 8.5mm Allowing +/- .003 for manufacturing tolerances would put you right in the ball park.
     


  9. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    @BudGates - I considered that in the OP as well. How common is metric sized chain in the US, and is 8.5 a common size of metric chain?
     


  10. BudGates

    BudGates

    Joined Apr 19, 2012
    897 posts, 76 likes
    Macgregor 26d
    US Ridgecrest CA


  11. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    Interesting chart, and obviously incorrect in many places. For the table that covers the short-link version of this chain, the measurement for "inside length" is the same as the measurement for "outside length", for many of the listed sizes (including the 8.5 mm). Doesn't inspire confidence in the company's ability to hand out correct specifications.
     


  12. BudGates

    BudGates

    Joined Apr 19, 2012
    897 posts, 76 likes
    Macgregor 26d
    US Ridgecrest CA
    According to both the drawing and the second chart "b" is the outside width not outside length as it says in the first chart. It stands to reason that they would be close if not the same.
     


  13. SFS

    SFS

    Joined Aug 18, 2015
    780 posts, 105 likes
    Hunter 31
    US Tampa Bay
    Ah, now I can translate the odd symbols to "b" and "d". Yeah, it makes sense that the two would be close on a short link chain. Column header sure is misleading.
     


  14. MitchM

    MitchM

    Joined Jan 20, 2005
    323 posts, 27 likes
    Nauticat 321 pilothouse 32
    US Erie PA
    and remember if you have a windlass that you need HT or BBB anchor chain, in the compatible size for your windlass gypsy.
     


  15. Ron20324

    Ron20324

    Joined Jan 22, 2008
    4,878 posts, 211 likes
    Beneteau 323
    US Annapolis MD
    [QUOTE="MitchM, if you have a windlass that you need HT or BBB anchor chain, in the compatible size for your windlass gypsy. [/QUOTE]

    And you can get gypsies in differing sizes for most windlasses.
     



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