Greetings.  

I would like to make inquiry on measurement for twist.

Please refer to section 5.4.2 of IPC-TM-650 number 2.4.22 rev B dated 
11/94.  In this section,
it is not mentioned if 3 corners are required to touch the datum surface 
when performing the
measurement for twist.  

(I have no problem interpreting section 5.4.1.  The method described 
clearly that both corners of
an edge are to touch the datum surface when performing measurement for 
bow.)

Please refer to section 5.2.2 of IPC-TM-650, no. 2.4.22.  "When the correct 
shim thickness is
used the three corners will be in contact with the datum surface" .   I 
interpret the statement has
an intend to ensure three corners are touching the datum surface when R1 is 
recorded.  If
positive, would it be appropriate to apply pressure on 3 corners when 
engaged section 5.4.2?

I appreciate your clarification.


Regards,

Isobel Tan
Tel. 65-750-4138
Fax. 65-751-6165

 

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