6 Laboratory Arts 



key to prevent misuse. A rag which has been soaked in a 

 mixture of two parts vaseline and one part paraffin wax should 

 be kept in a tin box in this case, and iron and steel tools 

 occasionally rubbed with this. 



The wood parts of planes should be rubbed, when new, in 

 similar manner with raw linseed oil (on no account may boiled 

 oil be used). This fills the pores on the surface, keeps out the 

 moisture, and helps to harden the planes so that they last 

 longer, and also take marks less easily. 



Sharpening. The sharpening of tools is an art in itself, 

 and one cannot do better than remark that " practice makes 

 perfect," though the practice of this precept is (usually) detri- 

 mental to the tools. However, one must learn, and tools are 

 nowadays constructed in such a way that allowance is made 

 for this " learning." 



" Sharpening " may be divided into two operations : 



( i ) Grinding. This is necessary when the cutting edge of 

 a tool ceases to be a straight line (or an even curve). When 

 a small piece is chipped out of a plane iron or chisel, the gap 

 always leaves its mark upon the work, and the defect should 

 be remedied at once. This can only be done by " grinding 

 back" a tedious operation, usually postponed as long as 

 possible, with the result that there is a tendency to alter the 

 cutting angle in order to secure a sharp edge. If, however, 

 the cutting angle is to be correctly retained, a large amount of 

 metal has to be removed by the oilstone a waste of time and 

 energy, and a source of detriment to the stone. 



A grindstone should have a width (" face ") of not less than 

 3", should be about 24" in diameter, and of fairly fine texture. 

 Gritty stones cut more quickly, but remove the metal in larger 

 pieces, consequently the subsequent sharpening takes longer. 

 Grindstones should never be used dry, as this takes the 

 " temper " out of the steel, yet must never be allowed to stand 

 in water, as this softens the stone. This softening would not 

 matter very much if distributed evenly throughout the stone, 

 but as the stone usually settles to one place on the frame, by 

 virtue of its centre of gravity, it softens most in one place. 

 This tends to make the stone of an oblate or eccentric shape, 



