GRIPPING DEVICES. 



129 



the specimen. Mr. Wicksteed forms his gripping surface 

 by cutting the face of the wedge with shallow grooves, 

 parallel and running along and across the face. These 

 grooves leave large teeth or projections which penetrate the 



FIG. 57. 



FIG. 58. 



surface of the specimen to be gripped. Some makers 

 prefer teeth of triangular section running only crosswise. 

 For the rapid testing of not very heavy test pieces some 

 engineers like to have the faces of the wedges coarsely 

 file-cut. 



The object aimed at in having the wedges resting in 

 the conical bush is to allow the wedges to accommodate 

 themselves to specimens which are not perfectly parallel, 



K2 



