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Looking for a screw?

  1. Nov 10, 2006 #1
    I'm looking for a couple of Allen screws hard to find I guess.

    Cap diameter 1/8 "

    Thread diameter 1/16 "

    Length: 3/4"

    I searched everywhere with no luck.
  2. jcsd
  3. Nov 10, 2006 #2


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    1/16 is smaller than what you'll usually find.
    It would help if you said what it was in standard size like #2-40.
    # is diameter -xx is thread count.
    Metric or SAE.

    Did you try local hardware stores?
    Hobby shops?
    Jewelry repair?
    If they don't have it ask them where you might find one.

    You could also try the company that made the unit for repair parts.
  4. Nov 11, 2006 #3


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    Allen screw doesn't really help. You need to be specific when looking at hardware. Are you talking a set screw? Socket head cap screw? What grade? Also, you do need to specify the thread class properly. When you say "thread diameter" is that the major or the minor OD? I would assume you mean the major OD.

    The closest you'll find to 1/16 is probably a 1-64 UNC. That has a pitch diameter very close to .0625. I don't know if you'll find anything that small with a length of .750 though.

    Looking through McMaster-Carr (the BEST website ever) this is about the closest you can find off the shelf. Go to www.mcmaster.com and do a search for part number 92196A069.

    If you can provide what you are doing we may be able to provide some more help. I'd also recommend aquiainting yourself with standard thread charts. You can find them all over the place. Here is an example:
  5. Nov 11, 2006 #4

    Thanks for the links, tons of parts there. I'm basically working with microwave waveguides. They are usually attached to one another with non-magnetic Allen screws. What I'm working here is an aluminum cube roughly 1.0" length, which has a WR-28 size waveguide hole milled into it.

    Wr-28 has dimensions 0.280 x 0.140 inches so you see it is small, and it is about 3/8 inch deep. There are also other holes 1/32" leading to the waveguide opening, and another two holes 1/16" in diameter that bypass the waveguide cavity. I want to basically attach a microwave connector (SMA) to the waveguide through two 1/16" holes. Allen screws would be nice because almost all of similar microwave components use Allen screws.

    I tried searching manufacturers of waveguide for parts, but still nothing.

    Also I'm not familiar with the standard size like #2-40

    Is it the thread size by length?

    This is what a microwave part looks like to give an idea.


    Here's one with SMA connector

    Last edited: Nov 11, 2006
  6. Nov 11, 2006 #5


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    Since I don't know what your physical or protocol constraints are, this might not be doable. Have you considered just redrilling and tapping the receiver bores to something easier to locate?
  7. Nov 11, 2006 #6


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    No. It represents diameter and thread count(pitch).
    length would still be 3/4".

    From the pic I would say that what you are looking for is called a "cap screw".
    Allen screws generallly don't have a head.

    If you had this part machined then you should be able to find out what the hole for the screw was taped as.

    Or as Danger says, pick a size you can get, that will fit.
  8. Nov 12, 2006 #7


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    Are the 1/16 holes tapped or are they simply thru holes? If they are tapped then you either would be looking at a 1-64 (coarse thread) or a 1-72 (fine thread). However, bolts that size do not need thread engagement that is .750 in length. I am still just a bit confused by the nomenclature of your part, but I think I get the gist. Judging by the second picture, you are you are looking for socket head cap screws (SHCS). You should be able to find 300 series stainless SCHS no problem.
  9. Nov 12, 2006 #8


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    Ding ding ding! :approve:

    I'm surprised Danger didn't misinterpret the title of this thread!

    I think the OP needs a 304 or 316SS socket head screw.

    . #2 is a spec of the thread diameters (look at links 2 and 5 at the bottom of this page: http://www.physics.ohio-state.edu/~kelch/ [Broken] ) and 40 tells you the number of threads per inch (inverse of the thread pitch). You can get a #2-40 (if that combination of dia and pitch exists - I've never seen one that coarse in a #2) in virtually any length you want.

    If I had to guess I'd thiink you want a #0-80 or a #1 socket screw, if the 1/16" inch holes are clearance holes, but you should probably go with a #2-56, if you are going to tap those holes. If the box material is some kind of plastic (like it seems to be from the picture), you probably want to tap a coarse thread (eg: #2-56, rather than a #2-64).
    Last edited by a moderator: May 2, 2017
  10. Nov 12, 2006 #9


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    Probably thinking of a 4-40.
  11. Nov 13, 2006 #10


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    It got my attention more quickly than most, but I had to factor in where it was posted.
  12. Nov 16, 2006 #11

    The first number refers to the Size (diameter) - small screws are given the size designations of 0 through 12, then they move to actual inch sizes of 1/4" and up. The second number is the threads per inch.

    A "0" size has an outside diameter of approximately .0595" so this is close to the size you describe. A "1" size has an OD of .0724" and a "2" an OD of .0854". In the business, we refer to them as a #1 or #2 etc.

    Almost all screw sizes come in a National Fine or a National Coarse thread size (refering to the threads per inch).

    To find the small screws you want, you need to visit a model hobby shop (that sells model planes and cars). Or you can buy online at a site such as www.microfasteners.com. They do carry both slotted head and/or socket head screws and they're available in carbon or stainless steel plus brass, aluminum and maybe some other materials.


    p.s. - not to forget the metric sizes, they come as 1, 1.5, 2, etc. sizes which refers to their actual diameter in millimeters. Since 1/16" equals 1.588 millimeters, you might be looking for a metric screw size 1.5.
  13. Nov 16, 2006 #12
    Most of the microwave stuff I've used have used either 4-40 or 2-56.

    What band are you using?
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