On Wednesday 25 April 2018 06:33:52 andy pugh wrote: > On 25 April 2018 at 00:53, Gene Heskett <ghesk...@shentel.net> 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 if its 18 thou thick, I ought to be able to form it over a 1/16" drill bit for a pin? That would work quite well then. > > 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. 1/2" I don't think is wide enough to lock into the follower. 5/8" wide might need some grinding of the edge as I recall the ends are tapered on at least one end. Will the grinding lead to early fatigue cracks? It might be needed to grind the folded edge to fit properly in the floor plate. I have a CBN wheel but its pretty coarse. > > [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 > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
