Tolerances in Precision Casting are effected by wax, shell composition and alloys.
Reproducibility of dimensions also depends on shape, mass and dimensions of parts. As mentioned in the
chart of tolerances up to nominal dimension of 15 mm is 0.1 and above 15 mm is 0.7%. However, the
tolerance range can be indicated is - or +.
The tolerance D3 in the chart can be obtaned at extra costs on one plane and for dimensions
without reference to each other (added operations, quality control mechanism, increase of wastage).
Machining Margins
Margins for machining should be left for dimensions of which the tolerance chart values
are not sufficient in view of usage of parts. Generally machining margin between 0.3 mm and 1.5 mm is left
with regard to dimensions. However, tolerance values should be taken into consideration while calculating
the machining margin.
Our aim is to decrease subsequent machining as much as possible. Therefore we recommend to contact our
technicians in respect of part design.
Linear Tolerances
| Dimensions |
Dimensions Tolerances (mm) |
Axial Tolerances |
| ..from |
...to |
|
| D1 normal |
D2 premium |
D3 limited |
D1 normal |
D3 limited |
| - |
6 |
0.10 |
0.08 |
0.06 |
0.25 |
0.16 |
| 6 |
10 |
0.12 |
0.10 |
| 10 |
14 |
0.15 |
0.12 |
0.09 |
| 14 |
18 |
0.20 |
0.14 |
| 18 |
24 |
0.25 |
0.17 |
0.12 |
0.32 |
0.20 |
| 24 |
30 |
0.30 |
0.20 |
0.14 |
| 30 |
40 |
0.37 |
0.25 |
0.17 |
0.50 |
0.30 |
| 40 |
50 |
0.44 |
0.30 |
0.20 |
| 50 |
65 |
0.52 |
0.38 |
0.23 |
0.71 |
0.45 |
| 65 |
80 |
0.60 |
0.46 |
0.27 |
| 80 |
100 |
0.68 |
0.53 |
0.30 |
0.90 |
0.60 |
| 100 |
120 |
0.76 |
0.60 |
0.33 |
| 120 |
140 |
0.84 |
0.65 |
0.35 |
1.15 |
0.85 |
| 140 |
160 |
0.92 |
0.72 |
0.38 |
| 160 |
180 |
1.02 |
0.80 |
0.40 |
| 180 |
200 |
1.12 |
0.88 |
0.43 |
1.80 |
1.00 |
| 200 |
225 |
1.28 |
0.95 |
0.47 |
| 225 |
250 |
1.44 |
1.05 |
0.50 |
| 250 |
280 |
1.64 |
1.15 |
0.56 |
2.20 |
1.25 |
| 280 |
315 |
1.84 |
1.25 |
0.63 |
| 315 |
355 |
2.10 |
1.40 |
0.73 |
2.60 |
1.60 |
| 355 |
400 |
2.40 |
1.60 |
0.80 |
| 400 |
450 |
2.70 |
1.80 |
0.90 |
3.10 |
2.00 |
| 450 |
500 |
3.00 |
2.00 |
1.00 |
D1 : Normal tolerances
D2 : Closed tolerances
D3 Limited tolerances (added operation at extra cost)
Geometric Tolerances
| Dimensions (mm) |
|
| ..from |
...to |
D1 (mm) normal |
D2 (mm) premium |
|
| 0 |
50 |
0.25 |
0.10 |
straightness |
| 51 |
130 |
0.50 |
0.30 |
| 131 |
255 |
1.00 |
0.50 |
flatness |
| 256 |
380 |
1.56 |
0.90 |
| 0 |
50 |
0.25 |
0.13 |
squareness |
| 51 |
130 |
0.75 |
0.25 |
| 131 |
255 |
1.25 |
0.50 |
| 256 |
380 |
2.00 |
0.90 |
| 0 |
50 |
0.25 |
0.13 |
parallelism |
| 51 |
130 |
0.75 |
0.25 |
| 131 |
255 |
1.25 |
0.50 |
| 256 |
380 |
2.00 |
0.90 |
| should be equal to the linear tolerances |
|
|
profile |
| should be equal to the linear tolerances |
|
|
holes |
|
0.5o |
1o |
angularity |
Surface Roughness
The surface of precision casting parts are quite smooth. The surface roughness
depends to a certain extent on dimensions of parts and casting alloys.
The values of roughness is between 10-30 µm in terms of Rt and between 3.0-6.0 µm in terms
of Ra i.e. in the roughness class N7-N9.
|
