Q. Explain the Chaplets.
OR
When are chaplets required in moulding practice? What is the material of the chaplets?
Ans. Chaplets : Chaplets are metal spacers used for supporting such large and odd shaped cores which cannot be adequately supported by their own core prints. They are placed in a mould between the mould face and the core. As the mould is filled up with molten metal the chaplets are surrounded by it and ultimately fused into it. The chaplet should be such that its head is larger enough to provide large bearing surface and this stem to fuse quickly into the molten metal. But this happens under ideal conditions only. In normal cases usually complete fusion does not occur, but the chaplet is very tightly gripped by the surrounding metal.
Material of the Chaplets
The material of the chaplet must conform to the molten metal or alloy being cast in order to effect proper fusion. For iron or steel castings, the chaplets are made of tin plate and low carbon steel. So the material of chaplets should be the same or very nearly the same as that of the casting to be made. The surface of the chaplets must be clean, without any trace of corrosion, moisture or oil. Chaplets are shot peened to increase their compressive strength and then tinned before use. Clean chaplets fuse well with the metal and do not cause the formation of holes and discontinuities.