Ok. Substitute "measurable" for "significant". We are talking alpha-brass, less than 34% zinc. Lesser brasses are not used for agraffes to my knowledge. In a message dated 3/5/2009 3:39:54 P.M. Central Standard Time, JD at Pianomaker.co.uk writes: At 11:06 -0500 5/3/09, PAULREVENKOJONES at aol.com wrote: >There is a mythology here that begs correction. Brass is not >"self-lubricating". There is no "lubricity" to it at all. There is a >significantly lower friction coefficient between brass and steel >than between cast iron and steel particularly because of the >different galling characteristics of them. It depends what you mean by "significant". So far as I can see, the coefficients of friction hard steel/brass and hard steel/cast iron are not very far apart. The coefficient for steel/steel is far higher than either. For copper-lead alloy or leaded bronze the coefficient is really significantly lower. But it is no use going simply by the figures in engineers' handbooks. The slightest amount of lubrication will greatly alter the friction coefficient, and the behaviour of each pair of metals needs to be measured under lab conditions to arrive at any useful figures. Besides, there is not one single composition for the "brass" alloy. One thing seems to be certain, and that is that steel, and especially hardened steel, is a bad option unless it is lubricated. Brass or cast iron unlubricated have behaved to most people's satisfaction since the 1850s, with cast iron, in practice, being better, since there is not a sudden change from static to sliding friction. For a capo bar I would prefer solid bronze containing the optimum lead content. I'm no great lover of Bösendorfers but in this regard I like their choice. JD Some useful general information and tables can bee seen here: <http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm> **************A Good Credit Score is 700 or Above. See yours in just 2 easy steps! (http://pr.atwola.com/promoclk/100126575x1219957551x1201325337/aol?redir=http:%2F%2Fwww.freecreditreport.com%2Fpm%2Fdefault.aspx%3Fsc%3D668072%26hmpgID %3D62%26bcd%3DfebemailfooterNO62) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20090305/ab86b948/attachment.html>
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