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Figuring out screw size

Discussion in 'Maintenance, Tinkering & Embellishment' started by MyLegsAreOk, Nov 8, 2017.

  1. MyLegsAreOk

    MyLegsAreOk Gold Member Gold Member

    342
    Aug 31, 2017
    I'm trying to figure out the screw size to the Spyderco Karahawk's ring screw size. Do I need to buy one of those sizing charts or is there some trick to measure screw size without it?
    I can but screws in 0-80,1-72,2-56,4-40 etc. but know for sure it isn't a 4-40. I measure and do calculations but nothing matches up with what niph khits dat cam has.

    I plan to buy a chart with my screw purchase because this keeps happening with Spydercos. For now is there anything I can do with simple tools at home?
     
  2. adamlau

    adamlau

    Oct 13, 2002
    Home Depot, Lowe's or your local hardware store should have public thread checkers available.
     
  3. tiguy7

    tiguy7 Gold Member Gold Member

    Jun 25, 2008
    Here are a couple of thread charts that I gleaned from various machinery handbooks. The first column is the nominal size (wire gauge 2 4 6 or diameter in inches or mm). BA is a British standard. The second column is the major diameter (outside the thread) of the screw in decimal inches. The next columns include National coarse, National Fine, National Special, Isometric, British Standard Whitworth, British Association, Lowenhertz, International Metric Fine, and French System.
    The numbers in these columns are TPI (threads per inch). The metric threads do not come out even because their system is calibrated in mm/thread.
    If you want to measure screws, you need a caliper and a TPI thread comb (gauge). Metric thread combs are available.
    Going to the chart looking at a #2 wire gauge screw, the diameter is .086” and the coarse thread is 56 TPI.
    Going to the chart looking at a 2.5mm screw, the diameter is .098” and the coarse thread is 56.4 TPI or .45mm/thread.
    25.4mm/inch divded by .45mm/thread= 56.4TPI. 18A0C982-7785-4AD5-AEB6-864E533E9D32.jpeg 6CF3FB39-50B2-44FE-8871-75844567AD74.jpeg 49C1149E-8C9A-4BE3-BFA9-F4323C65D09F.jpeg
     
  4. Minnesota Man

    Minnesota Man Gold Member Gold Member

    848
    Sep 30, 2014
    Go to a local hobby shop. I've done that a few times. It's my luck because the guy that own the hobby shop near me is a knife guy and doesn't want anything for helping.
     
  5. tiguy7

    tiguy7 Gold Member Gold Member

    Jun 25, 2008
    Home Depot, Lowe’s, and hardware stores do not carry a lot of smaller TORX recess screws especially in metric sizes and stainless materials. Start with the knife maker supply outlets. You need to describe the screw by its length, diameter, thread pitch, material, head type, and fastener type.
    I need a 1/2”X#2-56 stainless steel button head screw with a #6 TORX recess.
     
  6. adamlau

    adamlau

    Oct 13, 2002
    Fastenal, McMaster-Carr. Hopefully, you have suppliers such as those in your neck of the woods. Personally, I reference the McMaster-Carr website with a Mitutuyo in hand.
     
  7. tiguy7

    tiguy7 Gold Member Gold Member

    Jun 25, 2008
    I have used Fastenal, but they want you to order in lots of 100. The same is true of Victor Machinery Exchange Inc.
     
  8. MyLegsAreOk

    MyLegsAreOk Gold Member Gold Member

    342
    Aug 31, 2017
    Alright I'm going to check out the hobby store that sells a lot of RC car stuff today then I'll try out Fastenal because I keep getting told to check that place out when I'm doing a lot of other projects.
     
  9. FuelBoat

    FuelBoat

    37
    Sep 28, 2016
  10. MyLegsAreOk

    MyLegsAreOk Gold Member Gold Member

    342
    Aug 31, 2017
    Update. I got a micrometer and thread counter but alas still no luck in finding the correct size let alone screws. So I just bought 1-72 because the 0-80s were too small and here these fit in the whole but the threads aren't right! God this is is so annoying, and I can't get in there to clean the rust because if I pop it open I'll loose the de-headed screw in there!

    I bought the thread counter at and micrometer at Fastenal and they couldn't help me measure so I bought both the 0-80s and 1-72s from knife kits. Never had a use for these before but I have them now, heh.
     

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