Forums Beginner Questions MD&R 30 alloy?


6 replies, 5 voices Last updated by markossifakakis 2 months, 1 week ago
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    This MD&R 30 lap came in a lot. I can’t find information online about it. Does anybody knows it’s composition? It seems harder than plain tin. I was wondering about the lead content and the safety of using one.

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    Gregory Hays

    A fellow member on Gemology Online board wished to have this message relayed to you. Evidently he is not a usfg member and can’t post.
    “According to MDR’s “the Book of Gem Cuts (vol. 2), the #30 is type metal, usually composed of tin, lead, and antimony.”

    I have this volume as well and a old MDR catalog that lists the different laps and in the volume 2 #30 is only listed as “Type” nothing else I see. Strange but true.
    But in a catalog it is listed as #30 TYPEMETAL with the following description: aluminum backed, precision machined. An excellent lap for Garnet, Topaz and Zircon using Linde A. A good lap for Tourmaline. Hardness 2.0, shipping wt.2lbs.

    Also just for further info the #28 is “TIN/TYPEMETAL” which I assume it is a mix of metals and they state as a hardness of 1.8 which I also assume that would mean more lead content giving a slightly lower hardness than the #30.

    But then #26 “TIN/LEAD” they state is 50%-50% and a hardness of 2.0.

    It appears they had their own hardness scale for the metals, but they did not disclose all the details of the metals.
    Maybe possible the gentleman on the GO board knows something more about the MDR laps in the comment “usually composed of tin, lead, and antimony”.
    Anyway hope that helps some.


    Alan Balmer

    Evidently he is not a usfg member and can’t post.

    Please tell your friend that he doesn’t need to be a USFG member to participate in the forums. He does have to register on the website. You have to be logged in to reply to or originate posts.


    Allan Beck

    The “friend” is here now! Lost a computer 4 1/2 years ago and didn’t get back until now (other than lurking)

    And Al, I still did re-join USFG. Y’all deserve my support.



    Thanks you Gregory and your friend for your reply. Old good leaded pewter, it makes sense. This helps a lot. I will avoid using it.


    Eric Hoffman

    In a way, using your old typemetal lap is a good way to keep it out of the land fill. Just don’t lick it, and especially don’t feed it to children 😉



    Tempting to 😋.. use it. Hard little bugger.

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