A 4-40 PEM nut typically requires a .166 diameter hole and a 6-32 requires a .188 hole. So if a 4-40 nut was installed in a.188 hole it will not grip the material properly and it will eventually fall out. You should not re-tap the threads to correct the problem or use a smaller screw. You can install PEM fasteners with a hammer and anvil however there are insertion machines designed for this task.
John KK9A Michael Blake <k9jri at mac.com> wrote: I received a call back from Elecraft Technical Support yesterday. It was quite difficult to come together on exactly which screws and embedded PEM nuts I was talking about in the bottom cover. Once we were in agreement on the screw positions I was talking about the technician looked at a bottom cover but was unable to determine the exact thread sizes as he was unwilling to remove the green protective tape which covered the holes. He was not really equipped to handle this mechanical sheet metal problem but was going to refer it to another group which could more easily address the problem. I initially got the impression that he thought that I was incorrect about the threaded nut (PEM nuts) error but I think we got past that. For clarification, if you have a new kit and would check, these are the steps where the problems arise: These are the steps in the Kit Assembly Instructions Page 15, figure 14 show six (6) 1/4" 6-32 BLACK FLAT HEAD SCREWS. The right hand two (2) 6-32 screw locations were equipped with 4-40 threaded nut inserts (PEM nuts) rather than the correct 6-32 threaded inserts (PEM nuts). The two (2) 4-40 BLACK FLAT HEAD SCREW shown in this figure were correctly equipped with 4-40 threaded inserts (PEM nuts). The same problem exists on the right hand side cover. Page 24, figure 32 instructs you to install four (4) 6-32 BLACK FLAT HEAD SCREWS. In this case the two rear 6-32 screw locations were equipped with the correct 6-32 threaded inserts (PEM nuts) but the front two locations were equipped with 4-40 threaded inserts (PEM nuts). At this point I am waiting to see what they find when they check their current supply of bottom covers and what their recommendation will be to correct the problem. I do have a photo but I do not believe I can attach it to the reflector. Michael Blake k9jri at mac.com On Jan 27, 2018, at 11:06 AM, Michael Blake <k9jri at mac.com> wrote: I am waiting on a response from Elecraft TS on this one but I thought I would ask if anyone else has encountered this problem on the KPA500 kit. On the bottom edge of both the right and left side panels there are places for three 6-32 flat head screws. The countersunk holes are obviously larger than those for the other 4-40 flat head screws. In my kit one of the three PIM nuts, for each side, was the correct 6-32 thread PIM nut and the remaining two had 4-40 PIM nuts installed in the bottom cover. When I had temporarily installed the left hand side panel in the middle of construction I failed to notice this and just installed screws that fit (one 6-32 and two 4-40) but during final assembly it became obvious that the 6-32 screws would not fit in 4 of the 6 positions. Thinking that they just had paint in them I tried tp run a 6-32 tap through one and it naturally seized up and twisted the PIM nut out. Not being the brightest bulb in the shop I tried that a second time and twisted out the second PIM nut. Fortunately these were both on the right hand side where there was room to slip two 6-32 hex nuts in place and I just used two 4-40 flat head screws on the left side. Hopefully Elecraft will be able to send me the correct PIM nuts to replace the four incorrect ones. That was my request in the email to Doug at tech support. I certainly would not want to replace the bottom coverl as that would require a complete disassembly of the amplifier. Has anyone else encountered this? Michael Blake k9jri at mac.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
