Metallurgy Of Cast Iron

CHAPTER LV.
STRETCHING CAST IRON AXI> KLEMKXTS INVOLVED IN ITS CONTRACTION*.-
What shall 1 allow for contraction? is a question
which the experienced pattern-maker will i;vm-rullv ask the moulder or founder before any patterns »»f importance are be^un. It is true, we have the stnvo-typed rule of allowing one-eighth of an inch per loot for contraction, and many pattern-makers and founders are so inexperienced as to aeeepl surh a rulr for the contraction of every form and thickness of a. pattern which their plant may be railed on to make. It is possible with the class of work whirh they make that such a practice may never' have led them into diOictilties, and henre they obtain an exprnVni't' whiVh would lead them to believe that then* are rm ruiiditit»ns calling for anything else than the making <»f all patterns one-eighth of an inch per foot lar^vr in t-vrry <!<-rection tlian the castings desired.
Moulders and founders of broad rxjKTirnrr in i-.rn-eral machinery work know that thriv will ^nuT-illy be a difTerenct* in the* contract ion in any U\<» forms that differ in their proportions, even whrn ponied with the same iron. Also the form of a mould ;md
* Read by tlu- author ;it {lu-jiH-i'ttng of tin: W
men's Association, at ilncugt», Nov. 20, 1-^05.d scale should be well filed or ground off from the sand end of the roll so as to have it free from foreign matter, similar as in the chilled or hardened end, to make conditions alike in each end as far as possible. Another plan for testing fusion is given on pages 231 and 314.