Chinese drawing hole/shaft fit puzzle

Chinese drawing hole/shaft fit puzzle
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Posted by: locomotive ^®

01/18/2007, 17:51:10

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I have a puzzling dimension on a chinese drawing. It is for a check valve guide in a hot water pump. The hole is dimensioned dia.82D6(+0.23) and the shaft dia.82de6(-0.46/-0.7).(dia. substituted for the diameter symbol and the -0.46/-0.7 numbers over one another as expected in a tolerance.) I would expect to read these per ANSI B4.2 - 1984 but the numbers in parenthesis don't jive with that interpretation. i.e. I would expect to see something more like dia.82D6(82.142/82.120) and dia.82e6(81.928/81.906). I don't see a column for de in the shaft charts. Also, the numbers in the parenthesis make sense for the application if they are interpereted as the basic hole size being 82.23 and the shaft size between 81.54 and 81.30. Some of the machinists have seen the fit on a similar American pump on the order of 0.030 in. Any ideas on what the Chinese were using for their fit information?

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