Robot grip on robot head not working satisfactorily

Now I have mounted on the robot head another type of robot grip I got from TaoBao. This grip works more or less OK if I turn the servo by hand.  However, when I try it again using the servo adjuster, though I checked that the servo does gives signals from 1mS to 2mS, the servo moves too little distance to move the gripping plates to move bigger distance.

In short, both this and the old grip which I tested earlier were not satisfactory.  I wonder if other hobbists are using servos modified to move more than 90 degrees.  Need to check this later.

.END