Scott, I recommend you get a copy of IPC-2221, Generic Standard on Printed Board Design. It covers this and whole host of pcb design issues. To answer your question, use the following method: First, find the minimum required hole size ... Min hole size, plated through hole = (at least .006" over Max lead diameter, but not more than .028" over min lead diameter). Min hole size, unplated hole = nominal lead diameter + (at least .006", but more than .020"). Then find your maximum hole size .. Max hole size = min hole size + hole tolerance range (there are charts for this, but you can use .008" [ +/- .004] for most applications (lead diameters below .063"). Land (pad) size = a + 2b + c, where: a = Max hole size b = min annular ring (again, more charts; I recommend .005" for plated through, and .012" for unplated holes). c = fabrication allowance (even more charts; I recommend at least .012"). Hope this helped. Michael Hiteshew Lockheed Martin Launching Systems [log in to unmask] (410) 682-1259 > ---------- > From: Scott Rebman[SMTP:[log in to unmask]] > > I am in the process of laying out a new single layer PCB. > I find that the Protel library supplies components with .032 holes with > .050 pads. > On other existing PCB's I see that the components with .032 holes have > .077 pads. > No one hear can tell me why. > Does anyone know of standards for hole Vs pad sizes? > > Thanks > Scott R. > > ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################