$$3$$ blocks of $${B_1},\,\,{B_2},\,\,{B_3}$$ are to be inserted in a channel of width $$'S'$$ maintaining a minimum gap of width $$T=0.125mm,$$ as shown in fig. For $$P = 18.75 \pm 0.08,\,$$ $$\,Q = 25.00 \pm 0.12,\,$$ $$\,R = 28.125 \pm 0.1$$ and $$S=72.35+X.$$ The tolerance $$' X '$$ is _______________.

A metal strip is to be rolled from an initial wrought thickness of $$3.5$$ $$mm$$ to a final rolled thickness of $$2.5$$ $$mm$$ in a single pass rolling mill having rolls of $$250$$ $$mm$$ diameter. The strip is $$450$$ $$mm$$ wide. The average coefficient of friction in the roll gap is $$0.08$$. Taking plane strain low stress of $$140$$ $$MPa,$$ for the metal and assuming negligible spreading, the roll separating force is . . . . . . . . .

Welding of $$C40$$ steel plate of $$10mm$$ thickness required a current of $$16$$amps, while it was $$360$$amps when the plate thickness was increased by $$50\% $$. Estimate the welding current for $$8mm$$ thickness of same material.

In a typical metal cutting operation, using a cutting tool of positive rake $$\gamma = 10\deg ,$$ it was observed that the shear angle was $$20deg$$. The friction angle is