Victor,
    Without seeing any pictures and making a giant leap of guess, is a flat washer out of the question? We use them on all holes used for mounting hardware. Just doing my part to ask the dumb question for the group to get it out of the way... :-)

Scott Decker – Staff Engineer, PCB 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
KE7MWT  AKA:PadMasterson
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Friday, August 17, 2018 7:54 AM
To: [log in to unmask]
Subject: [External] [TN] PWB PTH mounting Hole Damage

Fellow TechNetters:

   I am searching for hardware mounting selection guidelines for the purpose of avoiding future damage to PWB PTH external copper pad by retaining screw head.

Example pics and current dimensions have been sent to Steve Gregory, [log in to unmask]<mailto:[log in to unmask]>



Givens:

-          PWB PTH Slot Diameter, 138.450 mm

-          Screw Head Diameter, 159.640 mm

-          Screw Shank Diameter, 87.740 mm

-          Potential mating overlap, 21.190 mm



Victor,