Machine Shop Home | |||
Introduction | Shop Safety | Layout | Inspection | Bench | Cutting Fluids | Sawing | Drilling |
Types of Steel Rules The six-inch rule is considered to be the most convenient size to carry around. Many steel rules have a "hook" feature that provides an accurate "stop" at the end of the rule (figure 12). This can be used to set calipers, dividers, etc. and for taking measurements where it is not possible to be sure that the end of the rule is even with the edge of the work. Some workers refer to steel rules as "machinists scales."
Decimal inch dimensions are specified and read as thousandths of an inch. Decimal rules, however are not graduated in thousandths, but are typically graduated into 1 /10", 1/50", or 1 /100" (figure 16). A typical decimal rule may have 1/50" graduations on one edge and 1 /100" graduations on the other edge. As the inch is divided into 10 equal parts, each graduation is 1 /10" or 100/1000" (one hundred thousandths of an inch). On the edge that is divided into 1/50", each 1 /10" increment is further divided into 5 equal parts, making the value of each of these divisions .020 (twenty thousandths) of an inch. The edge that is divided into 1 /100", each inch is divided into 100 equal parts, with each part equal to 1 /100 or 10/1000 (ten thousandths) of an inch.
Examples of Decimal Inch Readings: Distance "A" falls on the second marked graduation. Thus the reading is 2 /10 or 200/1000" (0.200) inch. Distance "B" falls on the ninth graduation beyond the .20 graduation and thus can be read only on the 1 00th,, scale. The reading is .200" plus .09" or .290". This distance cannot be read on the .50 rule because the discrimination on this scale is not sufficient
Examples of Reading Metric Rules
Distance "C" falls at the half-mm mark between 31mm and 32 mm. The reading is 31mm plus one half mm or 31.5mm. Distance "D" falls one half mm past the 4 cm graduation. Since 4 cm are equal to 40mm, the distance is 40.5mm. |
©2000 Fox Valley Technical College. All rights reserved.