Lens alloy 117 is one of an interesting range of Bismuth based alloys to which the element Indium is added to give a substantially lower melting point. Lens alloy is a eutectic, ie it has a sharp meting point, in this case only 47ºC. At this low temperature it has proved ideal for use as a holding medium or 'Button' in plastic lens grinding. It is easily melted, applied and finally melted off and having extremely stable characteristics, can be re-used repeatedly.
Melting Point: Eutectic 47ºC
Weight lb/in3: Approx 0.33
Brinell Hardness: Approx 14.5
Growth After Casting: (Shrinkage) Approx 0.0002" Per inch
Lens Blocking alloy 117 is primarily used for Holding Plastic/glass lenses during grinding operations. It can also be used for proof casting where low temperatures are necessary.
Because of its low eutectic melting properties this Lens alloy has found uses in fuses for safety devices. Also fusible mandrels.