Rick, We have been using a hole location within .009"TP of the center of the hole location based on a datum established on the PWB. We locate 2 tooling holes which create a X-Y datum and a 0,0 point, and then all holes are to be within their designated X-Y dimension from the 0,0 point within .009"TP. So, unlike you, where your referencing the hole to the pad center, we are using a 0,0 point on a datum to reference all locations, pads as well as holes. This eliminates the buildup of tolerances. We have been requiring this for about the last 10 years with no problems. At first we had a problem with the PWB vendor, but that turned out to be the method of creating the drill files (bomb sighting). Once we gave them electronic drill files, we have been 'fat, dumb, and happy" | :) Hope this helps. Richard Hamilton Clemar Mfg. / Rain Bird [log in to unmask] > -----Original Message----- > From: Richard G Smith [SMTP:[log in to unmask]] > Sent: Friday, March 13, 1998 5:26 AM > To: [log in to unmask] > Subject: [TN] PTH Positional Hole Tolerance > > Hi All, > > Here's the issue: > > We specify in our fab spec that all holes are to be within .003" > of > their corresponding pad center (true position of .006"). We are > being > told by our fab house that this tolerance is unreasonably tight. > > Any comments??? > > Thanks, > Rick > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV > 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC web site (http://jefry.ipc.org/forum.htm) for > additional information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or > 847-509-9700 ext.311 > ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################