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  • inserted nut

    Probably not what they're called- had an idea the other day to solve a problem or two, where a bolt would be used both as a fastening device and a locating pin. For a bolt with a length of the shank unthreaded, you would insert the bolt through the first piece, then the second piece would be drilled out part way for the shank to enter, then the threads start. Normally, you might start with a pilot hole, then drill for the shank to whatever depth suits, then drill the rest of the way for the tap. The hole might get fairly deep to allow the tap to cut enough threads to accept sufficient length of bolt threads.

    Instead of tapping the hole, why not cross drill to intersect the first hole, making the cross drilled hole large enough to insert a short length of rod. The piece of rod would get the proper size hole through it for tapping the threads, then it would come out and be tapped right through. When put back in the cross hole, the bolt can thread through the full diameter of it for a good hold. You would trim the bolt to length to suit.

    I've seen this type of nut before, but I don't know what they're called. Seems to me that in many applications where you might normally need a blind hole, and a fairly deep one to suit the use of part of the bolt shank as an alignment pin, these would make fabrication a lot easier. You avoid deep drilling and deep tapping, both very often problematic.

    A person could make up a number of these 'inserted' nuts using a jig to make drilling and tapping them easier. I'm thinking of possibly a 3/8 or 7/16 diameter for a 1/4 inch bolt, or say 1/2 inch diameter for a 5/16 or 3/8 bolt- something like that anyway. Am I nuts ?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    That is quite a few extra operations to avoid simply tapping a hole. It also requires a lot more space in the part as well as close access to the side of the part and the removal of a good bit of the material. I can't think of many situtations where it would be preferable to tapping the hole.
    Free software for calculating bolt circles and similar: Click Here

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    • #3
      Sounds like barrel nuts. I've seen them used in assembling furniture.

      Last edited by Arcane; 06-02-2011, 03:39 AM.

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      • #4
        First thing I think of is motorcycle brakes. Old skool linkage rod stuff.

        I think you should just tap the damn hole. The counter bore for the smooth part of the bolt will have to be oversized because the threads are not concentric on most off the shelf bolts. A hollow dowel for location with the bolt running through it would be better.

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        • #5
          Furniture Nuts.

          I get a headache looking at those furniture nuts. If any of you have ever assembled any Ikea furniture then you know what I am referring to. I hate Ikea furniture. My wife likes it for our guest rooms.
          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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          • #6
            The secret to assembling that cheap furniture

            There is a secret to assembling that cheap furniture. It's hard for a man to do but it does work.
            First: Read and follow the directions exactly. Put the bits together exactly in the order described in the instructions. This so you have to put the fasteners once.

            Second: Do not over-tighten any hardware or fastener ... Ever. You must stop when the screws are just snugged up. Particle board is the some of the least forgiving stuff on earth There is no way that I know to repair stripped or broken particle board.

            I told you it was hard!!

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            • #7
              Ikea does sell furniture kits that are made from solid wood. I have a living room full and it has held up well for decades. I don't own any particle board furniture. It isn't worth buying.
              Free software for calculating bolt circles and similar: Click Here

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              • #8
                Barrel nuts, ok. Now I know what they're called.

                You're probably right, Evan. There might be the odd application where they would be suited, aside from woodworking.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #9
                  Barrel nuts are often used to hold a lead keel onto a boat.
                  Lead being a bit on the soft side, tapping it can be difficult, and the resulting thread not all that strong, so that's not an option.
                  And rather than having the keel bolts go right down through the keel so the nuts on the end are just where you can't get at them when the boat is out of the water and sitting on her keel, it's better to cross-drill for a barrel nut a modest distance down the keel. (The barrel nut should be shorter than the width of the keel so the ends of the holes can be plugged to prevent salt water getting at the dis-similar metals.)

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                  • #10
                    At least a couple of Aircraft use them for engine mounts.

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                    • #11
                      It's not a lot of fun to drill deep holes, then have to run the tap in deep enough to get you sufficient thread engagement before the bolt starts getting tight. To cross drill, then intersect that hole with a bolt shank sized bit is pretty easy and not time-consuming. So far the parameters are well known and fixed- there's no guessing whether you got the hole deep enough, etc.

                      It does remove more material than just tapping the hole, thus weakening the part. On the plus side again, you do not have to drill as deep, and you have no risk of breaking a tap in the part. Even if you do not use a barrel nut, the cross hole makes it easier to get the intersecting hole threaded through, giving a space for the tip of the tap to enter without having to cut a section of useless threads that the bolt will never use, plus giving an opening for cuttings to exit into instead of having to withdraw the tap a number of times to clear the cuttings out.

                      If the threads can be used right from the start of the hole (no counterbore for part of the bolt shank) then it still is quicker to drill the cross hole than it is to run the tap in and out enough to get a sufficient amount of usable threads in just a single hole.

                      I still think the idea has merit, especially where the tapping might be a bit difficult because of the material. I've just done several tapped holes in the edge of some old steel plate, and it was a bit nerve-wracking- I didn't want to break a tap, and it was tough going as it was. A new, quality tap would have made a difference-
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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