#4-40 Thread

  • Hi.. so the monome faceplate uses holes with a thread of #4-40 to secure the pcbs...

    now I'm looking at the Schaeffer faceplate designer and it offers 3 different thread options

    UNC (Unified Coarse)
    UNF (Unified Fine)
    UNEF (Unified Extra Fine)

    They all offer a #4 option... but which do I use and what is the relevance of the -40 part?


  • I was wondering exactly the same thing.
    And I wish to know if it corresponds to an US type of thread, or is it good for europe (france) ?

  • Yeah good point... I guess it actually makes more sense for me to get a metric thread as I am in the UK.

  • I am interested in what answers you get. Let's keep in touch.

  • I think I saw in an earlier thread was that the #4-40 was imperial, and using a metric one requires you make the holes on the pcb slightly bigger.

  • Here you go:

    Seems metric M3 bolts are slightly big.

  • aha ok. thanks man. I think I'll go for M3 and widen the pcb holes.

  • Also, are you going with a 1/4" plate?

    If it will be thinner then that, I think you'd be better off using bolts and not threading.

  • Yeah I think I am going to go with a 1/4" plate, it'll suit the enclosure I have planned much better.

  • according to pocket ref,

    40 threads per inch on a #4 is coarse thread

  • M3 bolts fit ok through my pcbs, some of them needed just slight persuasion (a few very gentle turns with a screwdriver) but they are fine.