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 *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************