Chapter XIV: =measuring Machines, Tools and Devices.=

=Standards of Measurements=, in various countries 341
Use of, by sight and by the sense of feeling 341
Variations in standard gauges 341
The necessity for accurate standards 341
The Rogers Bond standard measuring machine 342
Details of construction of 343, 344
The principle of construction of 344
The methods of using 345
The Whitworth measuring machine 345
The Betts Machine Company's measuring machine 346
Professor Sweet's measuring machine 347
Measuring machine for sheet metal 348
=Circle=, division of the 348
Troughton's method of dividing the circle 348, 349
Ramsden's dividing engine 349
The construction of 350, 351
Pratt and Whitney's dividing device 352
Practical application of 353
Index wheel, method of originating, by R. Hoe & Co. 353
Application of the index wheel (Hoe & Co.'s system) 353
=Classification= of the measuring tools used by workmen 354
=Micrometer Caliper= and its principle of construction 354, 355
=Gauges.= Standard plug and collar gauges 356
Methods of comparing standard plug and collar gauges 356
The effects of variations of temperature upon standard gauges 356
Plug and collar gauges for taper work 357
The Baldwin standards for taper bolts 359
Workmen's gauges for lathe work 359
=Calipers=, outside, the various forms of 360
Inside calipers 360
Calipers with locking devices 360
Spring calipers 360
The methods of holding and using 361, 362
Keyway calipers 363
The advantages of calipers 363
=Fitting.= The four kinds of fit in machine work 363
The influence of the diameter of the work in limiting the
application of standard gauges 363
The wear of tools and its influence upon the application of the
standard gauge system 364
The influence of the smoothness of the surface upon the
allowance to be made for drilling or hydraulic fits 365
Examples of allowance for hydraulic fits 365
Parallel holes and taper plugs for hydraulic fits 365
=Fitting.= Practicable methods of testing the fit of axle
brasses forced in by hydraulic pressure 366
Shrinkage or contraction fits 366
Allowances for 366
Gauge for 367
The shrinkage system at the Royal Gun Factory at Woolwich 367
Experiments by Thomas Wrightson upon the shrinkage of iron
under repeated heatings and coolings 368 to 374
Shrinking work, to refit it 374, 375