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Threaded inserts...

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  • Threaded inserts...

    Generally I have no issue with this type of insert with CNC router cut MDF.
    But every once in a while I have some sort of issue with them falling out
    even with them epoxy'd in and I have a few cross thread situations and
    it is a nightmare!

    What are you guys using?
    Click image for larger version

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    Guess xmax's age.

    My guess: 15. His grammar is passable. His trolling is good.

  • #2
    I'm just using wood screws into hardwood behind the MDF. Plywood didn't work as well hardwood. I've done blocks of hardwood but they need to be big enough to prevent splitting
    John H

    Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower


    • #3
      Hot-melt glued-in weld-nuts. You can also use tee-nuts if you break the prongs off.

      Here is a thread with my method:

      While I've never had a failure, I don't build a ton of speakers. But if I did have a nut cross-thread, I'd simply remove it by holding a 100-watt bulb to the flange for a while (to soften the glue) and then push it out with a screw from the other side.


      • #4
        T-nuts or hurricane nuts that are inserted from the rear so they cannot be pulled thru, still have the issue of cross thread which is pretty
        common. On the t-nuts you can grind or snap off the wings also you may have to grind off the side that faces the driver opening for


        • #5
          EZ Loc inserts with a flange with 8-32 threads. Drill a 1/4” hole and the go in with a 4mm Allen wrench. I sometimes add a little wood glue. I have never had an issue with them coming out or cross threading. Yes only T nuts if I have to. The have a tendency to cross thread.
          "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

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          • #6
            I might be the wrong person to ask, but I don't use MDF unless someone puts a gun to my head. Baltic birch is all I will use for anything unless it was like a home theater sub and then maybe....

            In any event, I always use 10-32 6 prong heavy duty t-nuts except on 18" speakers in which even I use 1/4"-20 6 prong heavy duty t-nuts. In regards to grinding off the portion that faces the basket opening of the baffle. I always use double thickness 5/8" Baltic birch and make the inner ring about 3/8" to 1/2" smaller in diameter so that the t-nuts are further back and there is no trimming. Not to mention it stiffens the baffle up significantly for the speaker to mount to. I wish I had a picture, but this cad print will have to do. The blue is the speaker. The magenta is the t nut. The green is the center-line of the 1/4"-20 SHCS threaded into the t-nut. You can see the different diameter baffle ring on the inside. I have never had anything cross thread use t-nuts with grade 8 SHCS.
            Last edited by STIchris722; 07-08-2018, 11:03 AM. Reason: grammar
            "I don't know everything and do not claim to. I continue to learn and that is what makes me human."


            • #7
              I use the OP's style of insert for subs. I put them in small wood blocks which I then glue behind the front panel.


              • #8
                Originally posted by Gordy View Post
                EZ Loc inserts with a flange with 8-32 threads. Drill a 1/4” hole and the go in with a 4mm Allen wrench. I sometimes add a little wood glue. I have never had an issue with them coming out or cross threading. Yes only T nuts if I have to. The have a tendency to cross thread.
                I agree. I like EZ lok threaded inserts w/flanges with matching screws.

                I drill the hole just slighly over-sized than what the package suggests (about 1/32" - 3-64" oversize), dab a little gorilla glue on the thread ridges, then thread it in from back-side until the flange is flush with the surface. The gorilla glue foams/spreads and locks it in place so it doesn't rotate on it's own. They can also be threaded in from the same side of the baffle that the screw goes in, but I prefer from the other side to get better clamping pressure. 1/4"-20 for 12"+ , #10-24 for 8"-12", #8-32 for up to 8" drivers.


                • #9
                  If your crossthreading them well,,,,,, that’s your fault. When inserting the screw start by turning it backwards until you feel it fall a little. Now you’ve found the beginning of each thread (screw and insert). A new screw and a new insert should be almost impossible to cross thread.

                  If your pulling them out,,,,,,your overtightening them! Buy yourself a torque limiting screwdriver. Most guys over tighten screws. It’s in our DNA! If a little is good, more has to be better, right?

                  Good luck, Mark


                  • #10
                    I use high quality 4 prong T-nuts (made in the USA) with a small amount of 30 min. epoxy.

                    First I use a transfer punch and the actual driver to carefully mark the centers of the mounting holes, then use my drill press to make sure the holes are perfectly perpendicular. Sparingly apply the epoxy to the prong side of the T-nuts, insert them into the through holes, set driver in place (preferably without a gasket), start all bolts by hand, then progressively tighten the bolts in a criss-cross pattern to draw the T-nut prongs into the backside of the baffle (MDF or plywood).

                    I have never cross threaded a bolt or had a T-nut spin or come loose, and I remove and reinstall drivers a lot. On hardwood baffles I usually just use black oxide wood screws or T-nuts with the same proceedure above minus the epoxy.

                    I purchased a bag of T-nuts once from PE...

                    The lowest possible F3 box alignment is not always the best alignment.

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                    • #11
                      Like others, I use EZ-Lok threaded inserts with flanges. Pick one up, and try to screw in the appropriate screw.
                      Every once in a while, you get a "dud" that just won't thread easily. Discard that insert.
                      Then Insert from the back. I will usually put a little epoxy on the outside threads as I insert them.

                      Then, after the epoxy cures, put a little oil on a paper towel and get a screw a little slick (just a little).
                      Thread that in by hand, make sure that it moves easily in and out. Save that screw, and repeat the process with a
                      new insert and screw. When you finally screw in your driver, there is no question that things will go smoothly.

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                      • #12
                        I like the EZlock inserts as well. On my current project, I found some very similar to the EZlocks, but the outer side of the shaft is knurled, and there are no threads on the exterior of the insert. Just tap in with a hammer in the appropriate hole and a block of wood for flush alignment.

                        Then I found out that 2 of the holes on same project are not thick enough to allow the length of these new nuts, and the EZlock I have are flangeless in the 8/32 size, but are also too long. Unfortunately, I will likely have to use T-nuts on these 2 mounts, and if I do screw them up, I can easily replace them.

                        The majority of the holes do not have rear access due to the way it's constructed (except the 2 mentioned above), and the EZ should work well there if needed. So I can't use the knurled from the rear as initially intended, either. Due to the double thick baffles, I actually was able to drill and thread/tap the holes for the midranges into the rear board, and no inserts will be necessary. I dripped some Elmer's glue into the holes before inserting the machine screws to insure they would hold up to the use implied.

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                        • #13
                          EZ-LOK sells three different types of threaded inserts. The type in the original post are called E-Z Knife, and they are designed for hard wood (not MDF!). They are available in brass or stainless steel. The brass might be best if you are concerned about rusting or wood acids, but the stainless steel versions are less prone to cross-threading, and they are MUCH stronger. I tried using the brass on cherry and kept destroying the inserts when I screwed them in--had to buy the stainless steel versions instead.

                          The type that are in the second picture are called E-Z Hex and they are designed for soft woods like MDF, and they also good for plywood. You can get them with or without the flange. They are made from a zinc alloy which doesn't rust, and they are strong enough to minimize cross threading. They are a lot less likely to pull out than t-nuts, and you shouldn't need glue with them.

                          T-nuts or hurricane nuts are sometimes OK for hardwoods, but I wouldn't use them for soft wood like MDF, unless you glue them in. For MDF, the E-Z Hex inserts are a very good choice.

                          EZ-LOK also makes a third type which is suitable for soft wood or plastics--they are called E-Z Fin or Finserts. I haven't used them, but it looks like they might be a good solution where you don't have a lot of room to drill the hole for an E-Z Hex, or where splitting might be an issue. They expand to bite into the wood when the screw is inserted.

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                          • #14
                            I used the E-Z hex in a MDF cab and it worked very well. I'd recommend getting the drive tool which makes insertion much easier.

                            E-Z LOK Drive Tool - Optional - Use with 329-4, 329-401, 329-428, 303-4, 303-428, 319-4, 319-428, 335-4, 450-6, 550-1420, 650-6, 400-4, 400-428, 400-M6: Threaded Inserts: Industrial & Scientific
                            "Everything is nothing without a high sound quality." (Sure Electronics)


                            • #15
                              biggest problem is not the system chosen but rather the distance to the edge with the driver mounting holes. Scan Speak is the worst for this as there is minimal material to enlarge for insert !