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Screw types and sizes

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  • Screw types and sizes

    I'm obviously new to this level of building. I have SEVERAL questions about screws, and how to figure out the less-than-optimal assembly manuals...

    (1) Can someone please explain to me the description of the screws involved in the manuals, such as PA2.0*8. I can gather that the 8 at the end is the length in mm, but the rest I have no clue about. (First of all, what's "PA"?, is this just 'Part'?)

    (2) I'm trying to build the RocHobby Waco (the model is absolutely beautiful, by the way, and I'm determined to do it justice). But screws in the various envelopes are for the most part unlabeled, and even by counting and trying to compare to instructions, I'm not sure what's supposed to be used where... Does anyone have any tips toward this particular plane?

    (3) I've read about JIS screws - are these JIS screws? I've managed to almost cam out the larger wing screws, and now I suspect this is the reason...

    (4) About JIS screws - what sizes would most of these be, perhaps the #00 and #01? If I need them, I want to get the right size screwdrivers? There are some really tiny screws (such as for the wing struts), can these still be JIS (what size?).

    Prior to this model, I've been able to easily figure out what's what, but in this case - yike!! Any help would be appreciated!!!

  • #2
    Re: Screw types and sizes

    Screws with A in the name, 'PA' or 'PWA', are self-threading screws, like wood screws, and cut into an un-threaded hole in the plastic; screws with M in the name, 'PM', are machine type, which fit into a threaded hole, as in a nut. The number after the letters is the outside diameter, so PM3x6 is a 3mm diameter machine screw that is 6mm long, not counting the head.

    Yes, all that have cross-point heads are JIS type, the larger ones will fit a #2 or #1, the smaller fit a #0 or #00. I find it best to get a set. I have a few sets of four: #00, #0, #1, #2, and at least one set of four: #000, #00, #0, #1. I have yet to use the #000, so the larger set is more universal, I think.


    • #3
      Re: Screw types and sizes

      I never would have guessed that the PA was for the self-threading types, etc. Thanks much for the info, WintrSol. Ordering a set now...


      • #4
        Re: Screw types and sizes

        The names had me puzzled for a while, too, but using the pattern of numbers, which I assumed was the diameter and length, I measured them all, which revealed the letter pattern. I don't really know what the W means, though; perhaps it's a wider than normal head.


        • #5
          RE: Screw types and sizes

          Buy digital calipers at Harbor Freight. They are inexpensive and very useful for a builder. You can check your unlabled screws with this. The Doctor


          • #6
            RE: Screw types and sizes

            Greetings Wintrsol,

            Man, great intel and information.

            "Most" manuals are pretty good and indicating which screw is which as far as diameter and thread count (length), of course when in doubt a simple and faithful ruler will help) but they aren't very forthcoming on the little lettering codes.

            Thanks for the logic and clearity.

            Clear Skies

            Bill L.
            in Okla.


            • #7
              I build mostly glow and go here for anything I need


              • #8
                Thanks. I had to look this up.