Computer Action Team



ME 437 – HW #8 SolutionsProblem 9-110.5 mm drillThe suggested size tolerance for drills from online source is about 0.15 mm. Drilling hold IT10 to IT11 tolernaces, for IT11 the size tolerance is 0.11 mm. Map program also gives a value close to 0.1 mm. Using the last estimate the size limits become 10.5-10.6 mmThe widest position tolerance necessary for the holes become TH = Hmin – Fmax = 10.5 – 10 = 0.5 mm Position tolerance value of 0.5 is easily obtained by CNC drilling process. Free assembly is assured.When specified separately – Size 10.5 – 10.6 and Position 0.5 When specified as combined tolerances – Size 10 – 10.6 and Position 0Problem 9-2As shown in Problem#1, the 10.5 mm drill is not going to work for the case of fixed fasteners when the drilling position tolerance is 0.5 mm. Using 11 mm drill THc = THt = TH = (Hmin – Fmax)/2 = (11-10)/2 = 0.511 mm drillHole size limits become 11.0-11.1 mmThe widest position tolerance necessary for the holes become 0.5 mmWhen specified separately – Size 11.0 – 11.1 and Position 0.5 (clearance hole only)When specified as combined tolerances – Size 10.5 – 11.1 and Position 0 (clearance hole). The position tolerance of the threaded hole is 0.5Problem 9-3Using a 12.5 mm drill the drilled hole size tolerance is 12.5 – 12.6 and the position tolerance becomes TH = 12.5 – 12 = 0.5 mm. With the zero position tolerance the hole size limits become 12.0 – 12.6 mm. When the slot fits a rail of size 76 (-0.05,0) the fit play would be less than 0.1 mm.Problem 9-4The center hole sizes combine to have a worst-case maximum play of 0.1 mm. The fixed fastener formula with a 10.5 mm drill results in 0.25 position tolerance for tapped holes and clearance holes. The position tolerance of clearance holes is converted to 0 position tolerance.Problem 9-7Using a drill size of 9 mm results in position tolerances of 0.5 mm. Converting that to zero position tolerance for the clearance hole lead to size limits of 8.5 – 9.1 mm assuming a 0.1 mm size tolerance for drilling. ................
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