Hi John, Generally, I look at precision as it relates to mils (.001 inches) Concerning the precision (and range) of numbers required for photoplotting, drilling, routing, etc. I think the following applies: In inches, 2.4 number format seems suitable. That allows numbers from 99.9999 inches down to 0.0001 inches in increments of one tenth of a mil (one ten thousandth inch). In millimeters, 4.3 seems suitable. Converted to inches, that allows numbers from 394 inches down to .00004 inches in increments of 4 hundredths of a mil (4 hundred thousandths of an inch). Hope I got all my "ths" right. Also, leading or trailing Zero suppression in gerber or tooling files minimizes file size. Also, I've never liked 2.3 format (inches) for gerber files. image distortion can result from the rounding. Regards, Mark -----Original Message----- From: John Foster [SMTP:[log in to unmask]] Sent: Wednesday, December 04, 2002 2:12 PM To: [log in to unmask] Subject: [TN] Question about resolution It seems that there are a lot of very experienced fabricators in this forum. I have learned a great deal from reading the posts. I started laying out boards in 1998, it is not my chosen profession but is starting to become my chosen profession. I enjoy it very much. When I started a old manufacturing engineer gave me a set of guidelines to follow and something's I am still figuring out on my own. With that said here is my question to the forum. Right now I am sending all my gerbers and drills out in millimeters in a 3,5 274x format. So that means I am calling out things at 1/100,000 of a millimeter. I know that this has to be way beyond etching tolerance and what a drill can hold on tolerance. This is kind of what I started with. I have begun to change all of my designs to a .05 millimeter grid. But I still have some old legacy stuff from when I really didn't know what I was doing. So my question is what is realistic. At how many decimal places in millimeters or mills does it become nonsensical and a waste of time for the guy or program that has to round everything off. What kind of tolerance can a modern drill hold? At what point does the photo plotter or direct imaging machine run out of gas? Once again I have learned a great deal from this forum and would appreciate any kind of response Thank You John Foster --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------