How to confirm the rough casting tolerance?

Sometimes, our customers will be wondered how to confirm the rough casting tolerance. According to our experience, the standard of BS6615:1996 and QSCRATA1981 can be used for solving this issue. 

Please see the following standard BS6615:1996, this standard is also as same as ISO 8062:1994, which has been taken as the standard for the rough castings.  From the standards, you can see that vacuum casting is 5-7 degree. The highest tolerance for sand casting is 8-10 degree, which means shell molding process can reach CT8 degree. The machine molding and automatic molding can reach CT9 degree. The resin sand castingcan reach CT9 to CT10 degree. The clay sand casting can reach CT10 to CT12 degree.  

However, this standard can not represent all dimensions. Sometimes, as for some mounting dimensions, the clients will have special requirements. Then the foundries should consider it, and can try to meet the special tolerance by grinding or machining.  

The deviation of rough casting dimensions are related with the strength of molding sand, compactness of sand mold, liquid iron temperature, chemical components, moisture of sand and workers' operation. Any small factor may cause the deviation of dimensions. Sometimes, too strict requirements are not realistic. Some level of deviation is inevitable although we also try our best to control the deviation as small as possible.

The following is the ISO 8062 1994 inches and SFSA 2000 standard. Please click here to see the ISO8062 1994 millimeter  (mm).

QSCRATA1981