CHAPTER XLIV.

=HARDENING AND TEMPERING.=

=Purposes= 460 To resist wear 460 To increase elasticity 460 To provide a cutting edge 460 =Manufacturer's Temper= 460 =Blacksmith's Temper= 460 =Color Tempering= 460 =Practical Processes= 461 to 464 The muffle 461 Warping 461 Rapidity of reduction of temper 461 Brown and Sharpe's practice 461 Waltham Watch Co.'s practice 461 Pratt and Whitney Co.'s practice 461 Morse Twist Drill Co.'s practice 461 Outside hardening 462 Heating in fluxes 462 Monitor Sewing Machine Co.'s practice 462 Hardening saws 462 Drawing the temper 462 1. Lying in an open furnace 462 2. Stretched in a frame 462 3. Between dies 462 Stiffening saws 463 Tomlinson Carriage Spring Co.'s practice 463 Columbia Car Spring Co.'s practice 463 New Haven Clock Co.'s practice 464

APPENDIX.

=Part I.--Test Questions for Engineers= 467

=Part II.--Dictionary of Workshop Terms= 473

FULL-PAGE PLATES.