Neglecting bearing friction between the screw In the machinists vise shown, the

Question

Neglecting bearing friction between the screw

In the machinists vise shown, the movable jaw D is rigidly attached to the tongue AB which fits loosely into the fixed body of the vise. The screw is single- threaded into the fixed base and has a mean diameter of 15 mm and a pitch of 6 mm. The coefficient of static friction is 0. 25 between the threads and also between the tongue and the body. Neglecting bearing friction between the screw and the movable head, determine the torque which must be applied to the handle in order to produce a clamping force of 4 kN.

Explanation / Answer

Br=540N, Qr(H comp)=,L=2p=4 mm,pi x d=12 x pi mm,

?=tan-1 (4/12pi)=6 deg , ?s= tan-1 ?s=19.29 deg.

?s+?= 25.3466 deg

Qr=540xtan 25.3466 deg= 255.80 N

Couple= rx Q =6mm X 255.80 =1535 N mm.

M=1.535 Nm.

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