16 



Popular Science Monthly 



STANDARD 



ADJUSTMENT 

 SCALt 



MEASURING 

 , POINT 



If a machine part is too small by one 

 twentieth the width of a hair, this measur- 

 ing scale can detect it 



A Measuring Machine More Sensitive 

 Than a Human Being 



THE average person has little con- 

 ception of the accuracy with which 

 it is necessary to work on some classes 

 of machinery. Ball-bearing parts, for 

 instance, are produced in large quanti- 

 ties, yet in some cases the limit of error 

 is placed at one tenth of one thousandth 

 of an inch or about one twentieth the 

 thickness of a human hair. Special 

 measuring appliances are needed to 

 make these fine measurements in a 

 commercial way because hundreds ot 

 du|)Iicate parts must be gaged per day. 

 'l"he human sense of touch is coarse in 

 comparison. 



The multiphing indicator illustrated 

 is a very satisfactory device for measur- 

 ing parts that must be accurately gaged 

 without loss of time. The machine 

 consists of a substantial Ijase-plate witii 

 an accurately' ground, hardened steel 

 facing and an integral stanilard carrying 

 a measuring appliance. The dial-intlica- 

 tor reads in thousandths of an inch, 

 eac-h graduation representing a one- 

 thousandth inch movement of the in- 

 dicator stem. 



Thi- work to be measured is placed 

 under the measuring point on the 



multipKing lever. As this is \-ery near 

 the fulcrum, a relatively slight motit)n 

 will be changed to one of ten times that 

 magnitude at the dial-indicator. If the 

 work is but one thousandth inch larger 

 or smaller than the standard, the pointer 

 of the indicator will mo\e over ten 

 graduations on the dial. An error of 

 one tenth of a thousandth will move 

 the pointer one graduation. The measur- 

 ing arm may be mo\ed up or down to 

 accommodate work of varying diameter, 

 and when gaging duplicate parts, it is 

 set by a standard master-disk of the 

 correct dimensions. Any de\Mation can 

 be easily detected by a comparatively 

 inexperienced of)erator. 



Lighting the Inside of an Oven 



Ali.\KER'S o\en, illuminated on the 

 inside, is a great advantage since 

 otherwise the contents cannot be closelj' 

 inspected, unless withdrawn from the 

 oven. An arrangement, suitable for 

 electric or gas lighting, is shown in the 

 illustration. The door is hinged to the 

 frame b>- means of pins. One pin is 

 provided with a counterweight to facili- 

 tate the action of the door in opening 

 and closing. The other pin has a crank- 

 arm. On an extension on the door is 

 mounted a knife-switch, with two short 

 fingers to engage with the crank-arm. 

 The opening of the door establishes an 

 electrical connection with a lamp moun- 

 ted in a casing near the door. If gas is 

 used, the crank-arm engages with the 

 shank of a vaKe which regulates the 

 How of gas to till' burner in I he casing. 



The act of opening the 

 oven door completes 

 an elcctricnl circuit for 

 lilthting the inside o: 

 the oven. A similar 

 arrangement can be 

 used for gas 



