It would be better/easier to simply sand off .010" from the bosses on the bottom of the connector, rather than exposing the fiberglass weave on the PWB. Any hole in the PWB that is not sealed will allow moisture inside the entire PWB. FR-4 weave is just like a sponge. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Decker, Scott UTAS Sent: Monday, August 22, 2016 9:37 AM To: [log in to unmask] Subject: Re: [TN] [External] Re: [TN] Spot Facing areas for mounting hole of connectors. John / Wayne, <--(John Wayne? ☺ ) The connector is a through hole mount and is a custom circular aircraft type 38999 if you are familiar with that type. It has 4 mounting bosses that make contact to the board and it’s those 4 areas that we are thinking of machining down on the board. Again, the amount is only around .010” or so and as John mentioned, I was also concerned about moisture getting into the weave areas and wicking into the board. I don’t believe it would get far and the areas are free of routing and any copper features, so I’m not too overly concerned, but that’s why I’m asking the group. Maybe I’m missing something and don’t know it… ☺ The other question will be if a board shop or will it need to be a machine shop that can do the operation if we go that way. I’ll pose that to our suppliers and see what I get from them. Thanks for the replies and I look forward to more info. Later… Scott Decker – Senior Analyst, Drafting & Design Services CID+ – Electronic Systems Center UTC AEROSPACE SYSTEMS 3445 S. 5th Street, Suite 170, Phoenix, AZ 85040 U.S.A. Tel: 602 308 5957 FAX: 602 243 2347 [log in to unmask]<mailto:[log in to unmask]> www.utcaerospacesystems.com<http://www.utcaerospacesystems.com/> CONFIDENTIALITY WARNING: This message may contain proprietary and/or privileged information of UTC Aerospace Systems and its affiliated companies. If you are not the intended recipient please 1) do not disclose, copy, distribute or use this message or its contents, 2) advise the sender by return e-mail, and 3) delete all copies (including all attachments) from your computer. Your cooperation is greatly appreciated. This Document Does Not Contain Export Controlled Technology Or Technical Data. From: John Burke [mailto:[log in to unmask]] Sent: Friday, August 19, 2016 8:05 PM To: TechNet E-Mail Forum; Decker, Scott UTAS Subject: [External] Re: [TN] Spot Facing areas for mounting hole of connectors. If you machine into the weave you clearly have a potential for moisture ingress??? Did you consider a jig and machine the bosses? Best regards, John Burke