

METHOD OF RIFLING. 313 



would cut a straight groove through the barrel on one of its 

 sides, if passed backwards and forwards through it. Next 

 come the two problems, first, how to cut a spiral instead of a 

 straight groove ? and, secondly, how is this spiral to be made 

 quick or slow ? That is, how shall we form a turn in one 

 foot, two feet, three feet, &c., at discretion ? It must be 

 noticed that the section of the rod is square, and that it 

 passes through a square hole in the plate d. Now, by 



DRIVING-WHEEL OF RIFLING MACHINE. 



twisting this square rod on itself, the cutter attached to 

 its extremity, as it glides through the hole, takes a corre- 

 sponding twist, and if this is made one in three feet, the 

 groove will be cut exactly of the same twist. Thus we have 

 both problems solved. The twisting of the rod causes the 

 groove to be spiral, while the amount of its twist settles that 

 of the barrel. We have thus shown how one groove is 

 made, and all that is necessary in order to cut two, three, or 

 any other number of grooves, is either to keep the barrel 

 fixed and alter the position of the plate d for each groove, 

 or to let the plate remain, and move the barrel in a corre- 



