Stuart, Are these impedance boards? Are they military? Are they high reliability? Have you had assembly problems in the past? What tolerances to you need on your hole sizes? Usually, fab houses have a +/- .003, which I believe is IPC standard for plated through component holes. Via holes usually have a wider tolerance something like +.003/- holesize. Non-plated through holes usually have a +/-.005 tolerance. So with spreads of 6 to 10 mils, the actual finished hole sizes may blend across your specified ranges. What I mean is that it is not practical to specify hole sizes only .003 apart unless you also specify a tight tolerance (and pay more) to get that specific finished hole size. Depending on your tolerances for the finished hole sizes, many fabricators will drill difference finished holes with the same drill bit anyway since the finished hole size will be well within your specified tolerance. If you absolutely have to have those hole sizes then specify tighter tolerances. Check with your fabricator to see if they can hold +/-.002. Check with the assembly house to see what tolerances they need on the holes. The more drills needed to fabricate a board, and the tighter the tolerance, drives the tooling setup times up, total drill times up, inspection time up, scrap rate up, and hence - cost up. $$$$$ Hope this helps. On Sat, 26 Sep 1998 06:51:54 -0700 Stuart Chessen <[log in to unmask]> writes: >Over the past year we have upgraded our CAD library. Each >component has it own pad and/or hole size in the library. I have noticed >this has doubled the number of different drills needed compared with >previous boards layout in years past . Some of the drills sizes >only vary by .003". > > What problems is this causing for the board fab house? ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866] ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################