ROUGHING. 



95 



i;he holes may be filled witli corks to keep out the grit 

 and dirt. When corks are used, the wear of the shoe 

 causes a burr to form round the edge of the hole, and 

 T^efore the sharp can be screwed in a "tap" must be 



-Steel sharps, screw. 



worked into each hole to clear the thread. One great 

 objection to this method is that as the shoe wears, it 

 becomes thiniier, and if much worn, the shank of the 

 "sharp" may be too long, and when screwed home, 

 cause pressure upon the hoof and consequent lameness. 

 To guard against this, steel "blanks" are used to pre- 

 serve the holes, and when a frost comes, they are 

 removed and the " sharps " put in. 



The blanks vary in height, and, of course, those least 

 in height are best for the horse's action, but they must 

 not be allowed to get so worn that it is impossible to 

 remove them. These blanks are shown below. 



Fig. 71.— Blanks, screwed. 



The "tapping" and "screwing" of shoes is expen- 

 sive, and in small shops must be done by hand. In.large 

 shops, a gas engine and a machine v/ould reduce the cost 

 very greatly, and if the system came into general use, 

 this method of providing against frost-bound roads could 

 be carried out at much less cost than now. With a view 

 to economy and simplicity, a sharp has been invented. 



