12 Laboratory Arts 



should be parts of radii of a circle having the elbow of the 

 operator for a centre, in order to secure good square blows. 



Chisels. Chisels are of several kinds, "firmer chisels," 

 " mortising chisels," etc. The former are used for all ordinary 

 work, though sometimes they have the front edges ground 

 away in order to permit of their use in a corner. A mallet 

 should always be used when heavy striking of a chisel is neces- 

 sary. Light striking is frequently performed by the hand, as 

 also is paring. Work requiring a chisel should be arranged 

 so that the tool may cut downwards, and if a bench is being 

 used, a spare block of wood may be interposed, in order to 

 save the bench from damage. Mortising chisels are made 

 with heavy blades, and handles specially designed to permit 

 the striking of heavy blows, as the chisel has to cut through 

 thick and heavy wood. 



Gouges are best described as curved chisels, and the 

 remarks previously made will apply equally well. 



Bradawl ("sprig bit"). This tool is used for piercing 

 wood before the insertion of nails. It has a sharp cutting 

 edge, which is inserted always across the fibres of the wood 

 in order to cut these ; otherwise it will act as a wedge, forcing 

 the fibres apart, and doing exactly what its use is intended 

 to prevent. 



The uses of the rest of the tools are well known, and where 

 any explanation is necessary, it will be given where the use is 

 advocated. 



The Bench. It is important that some suitable bench be 

 used for laboratory woodwork, if only 

 to prevent the otherwise certain use of 

 the laboratory tables. A bench should 

 not be higher than 2' 6", and may be 

 up to 2' wide, and as long as is con- 

 venient, not less than 4' 6" or 5'. It 

 should be made of stout 3" x 3" framing, 

 and a top of 9" X ij" or 9" x 2" boards 

 FIG. 5. of good hard wood, planed true. 



A planing stop of wood (not toothed 

 metal) is recommended, and a "Parkinson" instantaneous 



