On 25 April 2018 at 00:53, Gene Heskett <[email protected]> wrote:
> This is a flat leaf, bent in the shape of a W. S/B nominally 1/2 to 5/8" > wide, folded at 3 places around a 3/32 drill shank. What spec of steel > do I need? and how do I heat treat it to put the spring into it once its > been shaped/bent properly? You have touched upon my specialist subject here. I did a few years of metallurgical research looking for ways to increase the strength (and hence the power) of car seat-belt springs.[1] Such springs are so powerful that http://www.m-p.co.uk/mp-spring-guide.htm specifically warns against using them in clocks designed for older materials. High performance spring steels get their properties not from heat-treatment but from cold-working. The material is initially rolled to about 3mm thick then heat-treated to produce fine bainite or pearlite by heating to the transformation temperature and then quenching in molten salt at 450C or thereabouts (this gives a very fast quench but avoids forming Martensite). https://en.wikipedia.org/wiki/Austempering The material will have a strength of about 700MPa at that point, but subsequent cold-rolling to 0.2mm or thinner can push the strength as high as 3500MPa. (Wire drawing reduces in two dimensions, and wire can reach 4000MPa) Even at these high strength levels the steel strip is sold with a guarantee that it can bend over a 2R or 3R former. So, to make your W-spring, buy some clock spring from a clock spring shop, cold form it to shape, and don't even think of heat-treating it. Here is a 5/8" wide one on eBay. https://www.ebay.com/itm/371453904179 You can probably find a 1/2" one if you prefer. Or use your preferred vendor of clock repair parts. [1] http://gow.epsrc.ac.uk/NGBOViewGrant.aspx?GrantRef=GR/H83829/01 atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1916 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
