Engineering Measurement Dr. Juma Y. Alaydi Gauge Design

Gauge maker's Tolerance Outline 1 Taylor’s Principle 2 Wear Allowance 3 Gauge maker's Tolerance 4 Example April 18, 2019 Engineering Measurement

Taylor’s Principle Plug gauges Snap gauges April 18, 2019 Engineering Measurement

Gauge maker's Tolerance April 18, 2019 Engineering Measurement

Second system (Revised Gauge Limits). April 18, 2019 Engineering Measurement

Third system (Present British System). April 18, 2019 Engineering Measurement

Example 50mm shaft and hole pair of H7d8 as per I.S. specification D = Value of tolerance unit i= 0.45 +0.001D =1.5597 microns =0.00156mm Now hole is of type H and grade 7 = 16 i = 16* 1.5597 = 25 micron For shaft d8 Tolerance IT8 = 25i =25×0.00156= 0.0391mm. Fundamental deviation for ‘d’ shaft = - 16D 0.44 = - 16×38.7 0.44 = - 16×5 = - 80 microns = - 0.08mm. April 18, 2019 Engineering Measurement

and Work tolerance = - 0.0391mm. Upper deviation= - 0.08mm. and Work tolerance = - 0.0391mm. Lower deviation = -0.08 – 0.0391 = - 0.1191mm (1)Plug gauges. According to new system, 'Go' gauges are given 1/10th of work Tolerance in the tolerance zone and 'No Go' gauges, outside it. Since work is less than 0.09mm. So effect of wear in 'go' gauges is not considered Work tolerance = 0.025mm Limits for 'Go' gauges are 50.000mm. And 50.0025mm. for 'No Go' gauge, dimensions are 50+0.025 = 50.025mm. 50.025+0.0025= 50.0275mm April 18, 2019 Engineering Measurement

Go’ Gauge No Go’ Gauge Go’ Gauge No Go’ Gauge (2) Ring gauges Dimensions for ‘Go’ gauge are50-0.08=42.92mmAnd 49.92-0.0039=49.9161mm Dimensions for, ‘No go’, gauge are50-(0.38+0.391) =49.8809mm And 49.8808-0.0039=49.8770mm Answers: Plug gauge. Dimensions for Go’ Gauge No Go’ Gauge 50.000mm 50.0248mm 50.0025mm 50.0273mm Ring gauge: Dimensions for Go’ Gauge No Go’ Gauge 49.9161mm 49.8770mm 49.9200mm 49.8809mm April 18, 2019 Engineering Measurement

Thank You ! Dr. Juma