Metal Working Miscellaneous Notes 67 



such treatment they are usually amenable to withdrawing by 

 turn-screw or wrench. 



Metal studs or screws that have rusted in may usually be 

 removed after a day's soaking in paraffin oil. Screws that are in 

 important positions, but have become worn or partially stripped, 

 may be temporarily rendered workable by " burring " the threads. 

 This is done by withdrawing the screw, placing on an anvil, and 

 giving it a light tap with a hammer across the threads. These 

 are thus closed up slightly, and the screw, if of soft metal, loses 

 its cylindrical shape, and so fits a portion of its aperture tightly. 

 This is, of course, a temporary expedient only, as once advancing 

 the screw generally brings it back to its old state, and the only real 

 cure is a new screw. The above method will, however, be useful 

 in cases of emergency. 



Similarly, a stripped nut may frequently be made to continue 

 useful duty by delivering two blows simultaneously upon opposite 

 faces with two hammers. Stripped union nuts, e.g.^ may fre- 

 quently be remedied by this means, as stripping is often due to 

 squeezing outwards rather than to the actual removal of the whole 

 thread. 



Fine wing drills may be made with success from good knitting 

 needles, which are, when well made, about the 

 right temper. Drills so made by grinding on a ^ Cutting 

 wet grindstone cut brass excellently, and wood, 

 vulcanite, amber, and similar materials, with 

 great ease. The drills should be first ground 

 on opposite sides to a taper, and then the neces- 

 sary clearance for waste material ground out. JT o~- T' 

 The cutting edges are next ground in, and, with wing drill. 

 care, the clearance for these may be given at 

 the same time. The finished drill will look like sketch. The 

 clearance angle is 5, and the angle between the cutting edges may 

 be between 100 and 120. 



Cast iron, brass, and gunmetal should be drilled with a dry 

 drill, but steel, either mild or hard, should always be well lubri- 

 cated with oil, or the temperature of the cutting tool will rise 

 beyond that at which it was tempered, and the drill consequently 

 become soft. 



Broken iron rods may be mended by thoroughly cleaning and 

 polishing the ends, and preparing an iron tube or sleeve that will 

 comfortably slip over the cleaned ends. A finely powdered mixture 

 of fine iron filings and ammonium chloride is then moistened, 

 smeared over the two ends, and the sleeve fixed on one end. The 



