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251.

Choose the correct statement in respect of die casting machine

A.	In hot chamber die casting machine the metal is melted in the machine itself	B.	In cold chamber die casting machine metal of low melting point is cast
C.	In cold chamber die casting machine there is no need to cool the die from outside	D.	none of the above

252.

A casting process which can produce cylinders by inserting cores into molten metal poured in the mould is

A.	Semi permanent mould casting	B.	pressed casting
C.	permanent mould or gravity die casting	D.	none of the above

253.

Aluminium is not a very good material for die casting because

A.	it is very light but strong	B.	its melting point is high, it erodes the die surface and tends to react chemically with die
C.	it cools much slowly	D.	none of the above

254.

Core prints are

A.	made separately in the mould by hand	B.	made in the mould be separate pattern
C.	attached to pattern	D.	none of the above

255.

In die casting

A.	the product surface is smooth and clean without the parting line	B.	there is no need of air venting
C.	there is no restriction of material, any material that can be poured can be cast	D.	the heat loss from molten metal is fast as the mould is metallic

256.

The thicker sections of casting will have a tendency to have

A.	grains coarser than thinner sections	B.	grains finer than thinner sections
C.	grains of sme size as rest of the casting	D.	none of the above

257.

A mould which has good erosion resistance to metal flow and is also collapsible is

A.	green sand mould	B.	skin dry sand mould
C.	dry sand mould	D.	none of the above

258.

The most suitable metals for die casting are

A.	zinc and its alloys	B.	copper and its alloys
C.	aluminium and its alloys	D.	none of the above

259.

Moulding sand properties that depend upon size and shape of grains and bonding material are

A.	permeability and plasticity	B.	plasticity and adhesiveness
C.	adhesiveness and cohesiveness	D.	cohesiveness and permeability

260.

Mixing coal dust with moulding sand results in

A.	blackening of the mould	B.	strong mould
C.	good air venting	D.	none of the above