Dear Scholars, I would like to know if there is information available, or opinions that address this subject of torque. September 20, 1995 Our design engineers have requested a torque specification for a circuit board. This is a two layers board, FR-4 material, thickness 0.062", and copper is 2oz. This torque requirement is due to a mechanical assembly operation. We are inserting a threaded SCR through the circuit board, where we will secure this device with a lock washer and nut. This assembly operation is very similar to your (IPC'S) description on page 10, fig. 2-10 of the "Acceptability of Electronic Assemblies," the only difference is there is no insulating washer. I do have the torque specification for the part being assembled which is 22 Lb.in (US-units), and I found no problems with this pressure. Still the design engineer is requiring the torque specification for the FR-4 product. Can you please assist me in qualifing this torque requirement. My first concers are, could an assembler tighten this part tight enough to crush the barrels or feed-throughs. "I will answer that myself," if no constraints are given, sure with a big enough vise or lever damage would occur. Sincerely your, Medar Inc, Michael Cussen