Investment Castings Tolerance

Cast alloy chemical specification Cast designations of comparable Cast mechanical properties Die casting zinc & aluminum Die cast mechanical properties Die cast physical properties Aluminum alloy comparable Linear tolerance Straightness, flatness & parallel Holes and channels Geometrical tolerance Surface quality Machining allowances Liner soluble glass castings

Investment casting ( ‘ lost wax ' ) tolerances are specified by the international standard: DIN VDG P690. As a general rule normal linear tolerance on an investment casting can be + 0,75% of the nominal dimension, with a minimum of + 0,10 mm for dimensions lower than 15 mm in order to achieve closer tolerances, a machining allowance is required, you can refer to general tolerance on machined parts but never forget that an investment casting always permits to reach very complex geometries. As a good rule severe tolerances are to be avoided if not necessary to allow the higher production yields and lower piece costs. Therefore, functional or closer dimensions must be pointed out in the drawings and deal with the technical department. The cast tolerances in the tables below can be used as an indication, depending on the steel alloy used and the product geometry. Linear Tolerance METRIC - Millimeters Tolerance class Range D1 D2 D3 0 to 6 ±0,10 ±0,08 ±0,06 6 to 10 ±0,12 ±0,10 10 to 14 ±0,15 ±0,12 ±0,09 14 to 18 ±0,20 ±0,14 18 to 24 ±0,25 ±0,17 ±0,12 24 to 30 ±0,30 ±0,20 ±0,14 30 to 40 ±0,37 ±0,25 ±0,17 40 to 50 ±0,44 ±0,30 ±0,20 50 to 65 ±0,52 ±0,38 ±0,23 65 to 80 ±0,60 ±0,46 ±0,27 80 to 100 ±0,68 ±0,53 ±0,30 100 to 120 ±0,76 ±0,60 ±0,33 120 to 140 ±0,84 ±0,65 ±0,36 140 to 160 ±0,92 ±0.72 ±0.38 160 to 180 ±1,02 ±0.80 ±0.42 180 to 200 ±1.12 ±0.88 ±0.43 200 to 225 ±1.28 ±0.95 ±0.47 225 to 250 ±1.44 ±1.05 ±0.51 250 to 280 ±1.64 ±1.15 ±0.56 280 to 315 ±1.84 ±1.25 ±0.63 315 to 355 ±2.10 ±1.40 ±0.71 355 to 400 ±2.40 ±1.60 ±0.80 400 to 450 ±2.70 ±1.80 ±0.90 450 to 500 ±3,10 ±2.00 ±1.00 Tolerance for straightness, flatness and parallelism METRIC - Millimeters Tolerance class Lengths D1 D2 D3 to 25 mm 0,15 mm 0.10 mm 0.10 mm 25 to 50 mm 0.25 mm 0.20 mm 0.15 mm above 50 mm 0.60 % 0.40 % 0.30 % Dimensions for holes and channels Dia. resp. □ Greatest length, depth respectively d (mm) continuous blind ≧ 2 to 4 ~ 1 x d ~ 0.6 x d ＞ 4 to 6 ~ 2 x d ~ 1.0 x d ＞ 6 to 10 ~ 3 x d ~ 1.6 x d ＞ 10 ~ 4 x d ~ 2.0 x d Geometrical tolerance Properties METRIC - Millimeters Symbol Circularity ±0.10 per 20mm Cylindricity ±0.10 per 20mm Profile accuracy ±0.15 per 20mm Profile accuracy ±0.10 per 20mm Angular accuracy ±30' Position accuracy ±0.10 per 20mm Concentricity ±0.10 per 20mm Symmetry ±0.15 per 20mm Run - out ±0.10 per 20mm Surface quality Degree Roughness values Ra (μm) Rz (μm) CLA(μm) N7 1.6 6 - 8 63 N8 3.2 12 - 16 125 N9 6.3 23 - 32 250 Machining allowances Operation METRIC - Millimeters For grinding 0.1 to 0.3 mm For machining 0.1 to 0.3 mm Liner tolerance for soluble glass process investment casting available in optional Degree Roughness values CT-5 CT-6 CT-7 0-10 0.36 0.52 0.74 10-16 0.38 0.54 0.78 16-25 0.42 0.58 0.82 25-40 0.46 0.64 0.90 40-63 0.50 0.70 1.00 63-100 0.56 0.78 1.10 100-160 0.62 0.88 1.20 160-250 0.70 1.00 1.40 250-400 0.78 1.10 1.60 400-630 0.90 1.20 1.80 630-1000 1.00 1.40 2.00 1000-1600 1.60 2.20 1600-2500 2.60

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