Hurricane Nut (T-Nut) Evaluation

[David_D]

I thought there maybe some people interested in what I am doing here. I know most people use wood screws to mount drivers and such but; I guess I'm just stubborn

1 Background
I am a custom machinery builder by trade. The mechanical designer in me really wants to use machine screws. My last project two of these nuts stripped their holes and spun on the screw during assembly. That is unacceptable.

2 Goal
Try and find a better way of installation to hold these nuts better so they may be used without worry of stripping.

3 Materials
1. ½” MDF
2. Gorilla Glue
3. ‘C’ Drill Bit (.240” dia)
4. 1/4” Drill Bit (.250” dia)
5. ‘G’ Drill Bit (.260” dia)
6. 36pcs #10-24 Hurricane Nuts (McMaster #90598A011) (pic #1)

4 Method
I will drive test batches of H-Nuts into smaller holes, factory recommended holes, and larger holes, some with Gorilla Glue binder.
1. 6 samples driven into ‘C’ Holes
2. 6 samples driven into ¼” Holes
3. 6 samples driven into ‘G’ Holes
4. 6 samples driven into ‘C’ Holes with glue
5. 6 samples driven into ¼” Holes with glue
6. 6 samples driven into ‘G’ Holes with glue
7. Test Bonds

5 Preparation
1. Chased each nut with a #10-24 tap. Noticed better then half of H-Nuts used had some kind of burr or hesitation on the internal threads.
2. Rinsed H-nuts is a bowl of Lacquer Thinner to remove many cutting oils from the machining process.
3. Drilled a grid of 36 holes into ½” MDF (pic #2)
12 - ‘C’
12 - ¼”
12 - ‘G’
4. Hammered 18 H-Nuts into dry holes
6 - ‘C’
6 - ¼”
6 - ‘G’
As one would suspect it was harder to drive H-Nuts into the smaller holes but, not uncomfortable particularly if supported well.
5. Applied a small bead of gorilla glue to the fillet of remaining 18 H-Nuts and hammered them into remaining holes. (Pic #3) (Pic #4)
6 - ‘C’
6 - ¼”
6 - ‘G’
The glue aided in the insertion process the ‘G’ Holes could be inserted by hand.
6. Applied a block and clamps over glued H-Nuts so the gorilla glue could not back the nuts off as the glue expands. (Pic #5)

:Z :Z :Z :Z :Z
I will follow up with test results.
-David

[Jim Holtz]

Hi Dave,

Cool! Hurricane nuts have frustrated me and many others just about every time we use them. If you can come up with a "better mouse trap" so we can use machine screws, we will all appreciate it greatly! :T

Jim

[David_D]

Thanks Jim,
We'll see what happens when the glue dries.
-David

[JonW]

David,

Looks like a nice, scientific test there. One that should help out others on the board. Excellent job. :T

I’ll share what I did in case it’s of any help. I tested a few things as well but not in such a rigorous manner as you are doing. I’m using Russian Baltic birch ply instead of MDF. So your milage may vary, etc. I can look up the details if anyone cares but I think it’s Reports hurricane nuts and a 1/4” drill bit.

My cabinets have an inner “rim” of bracing, as shown in the first photo below. I wanted to put the hurricane nuts around that rim, on the inside, so that I can screw in the rear baffles, shown in the second photo. On scrap I tried various drill bit diameters. I settled on a bit for making a hole that the hurricane nut can *not* be pushed in by hand. The hole is a too small for that. The shaft of the nut barely fits in the hole a little bit but the barbs certainly cannot go in at all, even when pressing hard by hand. The shaft, without the barbs, does not go far in. So I know that when the nut is finally seated in place, it will not get stripped and spin around. It’s a very tight fit.

I can’t hammer or press the nuts into the braces- the nuts go on the inside of the cabinet. And I don’t want to hammer on my cabinet. I cannot press them in by hand (it’s too tight for that). So what I did was place a big fender washer on the opposite side of the wood (outside of the cabinet). And then put a screw of appropriate size through the washer, through the wood, and then into the hurricane nut. Then screwed the screw until it pulled the hurricane nut outward, pressed all the way into the wood. I stripped a bunch of screws and bent a few washers in the process. But it seemed to work quite well. Those nuts are in there quite tightly and I doubt they’ll be moving any.

I like your idea to use a little glue. It can only help. Good luck with your project. :T





Image not available

[David_D]

Thank You Jon,
I too do not like the idea of hammering on the cabinet. I think I would recommend doing like you suggested with the bolt & washer or maye drawing them in with a c-clamp.
I would think the H-Nuts would bite better in a smaller hole. I wanted to keep to MDF as this what I will be using to build futher projects.
I bet the H-nuts grab better in natural wood, like your BB.
-David

[Martyn]

I like machine screws too.

For the speaker shown in my avatar, I drilled clearance holes for the machine screws and then counterbored them from the rear. I chose the counterbore diameters such that I could press-fit self-locking nuts into them (this can only be a light press-fit). I plugged the threads with something first (can't remember what, but probably a piece of tissue) and pressed the nuts into a bed of two-pack epoxy. All the drivers have been in and out several times and I have yet to have a nut come loose. It was quite a lot more work than simply driving woodscrews, especially since I have nearly three dozen screws on the pair.

[megamuel]

What the hell causes cancer?

[Coconutout]

aw man, t-nuts were the biggest challenge in building my sonosub this time. just mounting the driver probably took as long as building the sub itself. i tried to glue them, however, the holes were not perfectly straight down and i kept pushing the nuts out with the screw. so in the end i duct taped the nuts so that i would have some play trying to meet the screws to the nuts in a not so perfect holes. so now I have a thoroughly built sonosub with one flaw... they have duct tapes inside... :P

[David_D]

What the hell causes cancer?

HAHAHHAHAHAHHAHAHAHAHHAHA!!!!! :rofl:

I was waiting for someone to notice. It's on all of our MDF Sheets. It's the glue binder, that's in question. It seems like even cotton candy causes cancer in Cali.

[David_D]

aw man, t-nuts were the biggest challenge in building my sonosub this time. just mounting the driver probably took as long as building the sub itself. i tried to glue them, however, the holes were not perfectly straight down and i kept pushing the nuts out with the screw. so in the end i duct taped the nuts so that i would have some play trying to meet the screws to the nuts in a not so perfect holes. so now I have a thoroughly built sonosub with one flaw... they have duct tapes inside... :P

Well, hopefully I can make some progress that no one will have a duct taped speaker.
We all have to have goals. :lol:

[David_D]

I like machine screws too.

For the speaker shown in my avatar, I drilled clearance holes for the machine screws and then counterbored them from the rear. I chose the counterbore diameters such that I could press-fit self-locking nuts into them (this can only be a light press-fit). I plugged the threads with something first (can't remember what, but probably a piece of tissue) and pressed the nuts into a bed of two-pack epoxy. All the drivers have been in and out several times and I have yet to have a nut come loose. It was quite a lot more work than simply driving woodscrews, especially since I have nearly three dozen screws on the pair.

That's a great idea Martyn,
It may indeed come to that because I WILL make these silly things work! :W

[Amphiprion]

The binder in MDF is urea formaldehyde glue. It off gases to an extent after being cut and perhaps even afterwards.

Good thing it only gives you cancer if you're in California, we Texans are safe

I stopped using cap screws and T-Nuts/H-Nuts. Not because I ever had a problem with them (I must be the only person that is true for) but because black pan head coarse thread screws work fine for me. I can pop drivers in and out multiple times with no problem. Set the torque on the cordless drill low so you don't tear up the MDF and use a sleeve-over-bit screw driver so you don't slip and put a hole in your woofer cone.

[atm98]

T-nut issue

Good thread. I agree this T-nut issue is a problem.
When I built my sub I used T-nuts. They tightened ok, but when removing the screw, the t-nut spikes “unbent” and lifted out of the wood. I ended up cutting some MDF blocks with 1/8” deep countersinks. The cut dia was just larger then the T-nut large diameter. These blocks were then installed behind the t-nut flats. This prevented the nut from lifting up. I have to watch the screw length as it will hit the block if screwed through the T-nut. Actually I drilled another smaller hole 3/8” deep in the center. Sorry no pictures I am in the process of moving.

Austin

[JonP]

Allright Dave!! Science in Action!!! OCD forwarding Human Knowlege!!! :W

Quite the detailed test.. this will be good. Heck, maybe you could write it up in detail, with a lot of pics, and send it to one of the woodworking magazines, or AudioXpress...

FWIW, I've had a limited experience with H-nuts... all good. I had heard about the occasional spin, so I was careful. My general plan was: to measure with calipers and pick a drill that was a hair smaller for good tension, but not too tight, wet the back surface of the nut with slow cure epoxy... (being real careful not to get it in the threads!) and use the washer and bolt method to pull it in snug.

Worked great in MDF for a Quatro 15 sub and a few other projects.

[Coconutout]

umm, ok... i've been reading up that MDF gives off formaldehyde even after being cut and the dust is all cleared off? like when its in your living room as a harmless furniture, its still giving off toxic gas?! i got a pair of statements that was covered with black velvet over raw mdf... I'm thinking a big formaldehyde alert. i know what ill be doing with my free time tomorrow... strip the statements, paint it up, re-velvet it... jeez. i don't get how they say painting it won't seal it up tho. i mean, you take acrylic or latex paint and it's basically a liquid plastic/rubber. it seals against moisture, air, so why can't it seal up the formaldehyde permanently?

[David_D]

Allright Dave!! Science in Action!!! OCD forwarding Human Knowlege!!! :W

Quite the detailed test.. this will be good. Heck, maybe you could write it up in detail, with a lot of pics, and send it to one of the woodworking magazines, or AudioXpress...

FWIW, I've had a limited experience with H-nuts... all good. I had heard about the occasional spin, so I was careful. My general plan was: to measure with calipers and pick a drill that was a hair smaller for good tension, but not too tight, wet the back surface of the nut with slow cure epoxy... (being real careful not to get it in the threads!) and use the washer and bolt method to pull it in snug.

Worked great in MDF for a Quatro 15 sub and a few other projects.

Thanks Jon,
You crack me up.
Your method is supporting my hypothesis. AKA smaller hole + Glue = better bite. I'll find out tomorrow morning.
Yea... I can't get enough of machine screws.
-David

[dlneubec]

I never cared for t-nuts and prefer to use threaded inserts like these:

[Rich Jura]

I have never hammered a 'T'nut , I always thought the proper method was to draw them into the wood with a screw and a couple of fender washers.An
allen head allows you to develop a mite more torque.McMaster-Carr also carries these nice brass threaded insert a 10-32 the part no. is 90016A021 $10 for a
pack of 25.
Thanks for the tip on the Freud Dado.


Later
Rich

[dlneubec]

To be more specific, the ones I've had the best luck with are called "flanged knife thread inserts for soft wood" from EZlock. They are available at MSC incustrial and probably many others. The knife thread inserts are much easier to thread staight into the hole as compared to the standard full threaded inserts, which for me, always wanted to thread in at an angle.

Flanged knife thread inserts

[eddo]

I've used the 1/4"-20 H-nuts with no problems so far. What I did was use a rather small hole, then press the H-nuts in with a vise. Alternatively, if using a vise isn't practical, you could press them in with a c-clamp. That method is nice if you need to install them in place once a panel is glued.

[stangbat]

I've only used Hurricane nuts for one project, but they worked well for me (7" drivers, 3/4" MDF). I pressed them in with a C-clamp and I used the recommended 5/16" bit size for the 1/4-20 nuts. Some of the holes I even had to enlarge a bit to get my driver to line up and I still didn't have problems. What was I doing wrong?

Is there a difference in how the 1/4"-20 work vs. the finer thread count versions of the nuts?

[David_D]

I've only used Hurricane nuts for one project, but they worked well for me (7" drivers, 3/4" MDF). I pressed them in with a C-clamp and I used the recommended 5/16" bit size for the 1/4-20 nuts. Some of the holes I even had to enlarge a bit to get my driver to line up and I still didn't have problems. What was I doing wrong?

Is there a difference in how the 1/4"-20 work vs. the finer thread count versions of the nuts?

I have heard from a number of people that have had no problems withe their individual procedures. I have heard from a number of people that are adamant that they will never use them again. Whose got the right answer IDK.
I will say that if the nut is going to fail or back out it tends to be right at the first initial start of the bolt. I have found that these nuts begin cross threading very easilly. I believe that is the common problem. I would also think that that is a phenomenon that get worst as the pitch gets finer.

I am happy you have a good procedure. As for me, even though I pay considerable attention to detail. I still had two of these buggers spin on me.
That will never happen again.

-David

[chasw98]

Lately I have ben building a lot of test cabinets, probably 12 or so in the last 2 months. I have used and reused Hurricane nuts on all of them plus on a lot of previous projects. One factor I have noticed that I didn't see mentioned is that, I believe, the h nuts are meant to be 'threaded' into the wood. I have always felt them turn when I am getting them seated for the first time in a baffle when using an allen wrench on a socket head cap screw. I don't believe they were ever meant to be 'press fit' or hammered into the wood.

Great idea and very helpful thread. I hope you come to solid a conclusion we can all apply.

Chuck

[David_D]

H-Nut Test Results

6 Metrics
The H-Nut should be able to withstand a certain amount of wiggling around of the bolt.
The force required to fish & wiggle a bolt in with a T-handle Hex Wench is 2 - 5 lbs.

7 Tests
1. Hand-thread a bolt into each H-nut and wiggle (subjective)
2. Insert bolt loosely into each H-Nut and press against a scale & record break force

8 Results
Global notes: All H-Nuts very susceptible to first initial cross threading.

1. Hand-thread a bolt into each H-nut and wiggle (subjective)

Pic#1

No surprise with the results here. Smaller holes = Better Bite
All H-nuts without glue transferred wiggle to the flange of the H-Nut. All H-nuts that had glue did not in the least.

2. Insert bolt loosely into each H-Nut and press against a scale & record break force (lbs).

Pic#2

Although a smaller hole does increase the break force of the H-Nut, the ones with Gorilla Glue bonded extremely well.

9 Conclusions
Over 50% of H-nuts tested had some kind of burr internal to the threads.
Chase each nut with proper size tap.
Great deal of machine oil on H-Nuts
Wash H-Nuts with quick evaporating solvent.
Hole size variance did play a part in dry installations, not so much in glued installations
Use recommended ¼” drill bit for installation ease.
Recommendation:
Couter sink small chamfer on hole inlet. As a lead, more surface area for glue, & keeps nut flange flatter.
Glue assists dramatically in overall strength
Use Gorilla glue to bond nuts in place (small bead in flange fillet to avoid getting into threads)
To avoid internal splitting of MDF
Draw in H-Nuts with Bolt & washer or C-Clamp
H-nuts are very susceptible to first initial cross threading
Start screws by hand

Hope this helps someone. I know it helped me.
-David

[David_D]

Lately I have ben building a lot of test cabinets, probably 12 or so in the last 2 months. I have used and reused Hurricane nuts on all of them plus on a lot of previous projects. One factor I have noticed that I didn't see mentioned is that, I believe, the h nuts are meant to be 'threaded' into the wood. I have always felt them turn when I am getting them seated for the first time in a baffle when using an allen wrench on a socket head cap screw. I don't believe they were ever meant to be 'press fit' or hammered into the wood.

Great idea and very helpful thread. I hope you come to solid a conclusion we can all apply.

Chuck

Hi Chuck,
The nuts I am evaluating do have angled "wings" on the vertical barrel. As they are inserted they twist in ~ 20 deg's. I chose those for my first (& now subsequent) project because they do not have the tangs that can tear up a driver hole edge and they require a smaller insert hole then some of the threading inserts that others have mentioned. A pic of the actual nuts I am discribing can be found on the first post.
-David

[Martyn]

If you try this, just be careful when you're relieving the back edge of the woofer hole. You might have to do a little free-hand routing to avoid machining the nuts!

[Amphiprion]

I have never had a problem with a T-nut that I hammered in. For those with problems, are you hammering them in or using another method?

[mikela]

If you try this, just be careful when you're relieving the back edge of the woofer hole. You might have to do a little free-hand routing to avoid machining the nuts!

It might be best to do this before installing the nuts.

David,

Thank you very much for doing this. It will definitely help me out...I was previously resigned to using wood screws. I took a vacation day so I could cut MDF for my Statements today

Mike

[mazurek]

be very careful if you use glue, and draw in the t-nuts with the machine screw/fender washer method. I had an accident where I got glue on the machine screw, and it bonded quite well to the t-nut when I took a momentary break. By the way, I hate t-nuts and hurricane nuts. I bought some knife thread inserts like mentioned earlier to try.

[David_D]

If you try this, just be careful when you're relieving the back edge of the woofer hole. You might have to do a little free-hand routing to avoid machining the nuts!

Here's one way out.
-David

[David_D]

David,

Thank you very much for doing this. It will definitely help me out...I was previously resigned to using wood screws. I took a vacation day so I could cut MDF for my Statements today

Mike[/QUOTE]

Hi Mike,
Glad I could help. Best of luck with your Statements Build. I can't wait to start my own. Don't forget to post pics.
-David

[David_D]

I have never had a problem with a T-nut that I hammered in. For those with problems, are you hammering them in or using another method?

I my particular case, I hammered in all the H-Nuts and two stripped/backed off. Knowing what I know now, it's Gorilla Glue & pressed in for me.
-David

[megamuel]

Christ, I knew the dust and glue in MDF is not good for you but I've never heard that they "Cause cancer"! Maybe increase your risk of getting cancer but not cause it. They don't even say smoking causes cancer do they?! Pretty scary, it doesn't say that on my MDF! Anyway, yeah, what was this thread about....

[mikela]

David,

Can you provide details on how you prepared the baffle with hurricane nuts? :T

Mike

[David_D]

David,

Can you provide details on how you prepared the baffle with hurricane nuts? :T

Mike

Sure Mike,
First I cut the driver recess using a Jasper Jig & router. Next I cut the through hole using a Jasper Jig & router. Then I set the driver in place & marked out the bolt holes. Then I drilled the bolt pattern through using a 3/16" drill bit. This is the pilot hole for the Counter Bore Bit. Then I flipped the baffle over and used a 3/4" Counter Bore bit to make the nut recesses. The depth was a guess, I just wanted to be sure I was below the heavy driver relief. Then I cut the rear relief for the driver with a 45 deg chamfer bit.
Lastly I opened up the bolt holes to recommended size of the H-nut and installed nuts.
My guess is your probably after my counter bore tool. ;-x
It’s a little different; it’s actually a metal spot face tool. (McMaster Carr # 3102A28 )
Attached is a pic :T
-David

[jkrutke]

For me, hurricane nuts have never stripped, and I've used about 300 of them. I wonder if I'm doing something different.

All that said, the main reason I've been using them is because I like the look and fit of socket head cap screws. Now that Madisound has socket head wood screws I tend to use those more than hurricane nuts. I still use hurricane nuts for larger drivers though.

[David_D]

For me, hurricane nuts have never stripped, and I've used about 300 of them. I wonder if I'm doing something different.

All that said, the main reason I've been using them is because I like the look and fit of socket head cap screws. Now that Madisound has socket head wood screws I tend to use those more than hurricane nuts. I still use hurricane nuts for larger drivers though.

That's worderful that you have never had a problem. Unfortunatly, there are many including myself that have. I'm sure it was a question of me/us doing something different.
Coming from a machine designer/builder background I figured while using these that i put sufficent thought into intergrating them into the design but, two still failed. One started to spin in the wood about two turns into the screw. The second backed out of the hole while trying to start the thread.
Knowing what I know now this will never happen again. It still sucks that there are two loose screws on my center speaker. I will continue to use them now that I have a good procedure.
I agree you can't beat the look of button head or socket head cap screws. :T

[Amphiprion]

Nice find Zaph.

[jkrutke]

Reading though this thread, I noticed one thing I might do different. After I drill the hole, (1/4" bit for the #10) I take a countersink bit and put a little chamfer on the back hole edge. After I do this, the hurricane nut sits flat on the back rather than resting on the little radius. Seems to make it more stable and bolts seem to wiggle less.

Here's an interesting tidbit: my testing baffle insert uses hurricane nuts. They're the same ones in it since I built the thing, and imagine how many times screws have been in and out of that.

[David_D]

Reading though this thread, I noticed one thing I might do different. After I drill the hole, (1/4" bit for the #10) I take a countersink bit and put a little chamfer on the back hole edge. After I do this, the hurricane nut sits flat on the back rather than resting on the little radius. Seems to make it more stable and bolts seem to wiggle less.

Here's an interesting tidbit: my testing baffle insert uses hurricane nuts. They're the same ones in it since I built the thing, and imagine how many times screws have been in and out of that.

Very observant. A C-Sink would be very helpful. Like you said, to keep the nut flat, a little clearence & more surface to bond (if one uses glue), and the added benifit of giving a small lead to help with insertion.
Thanks John will do that.
-David

[Martyn]

Very nicely done!

[mikela]

David,

Thanks for the details. Nice work! I also like the look of the black oxide hex heads.

Mike

[JonP]

Sure Mike,
First I cut the driver recess using a Jasper Jig & router. Next I cut the through hole using a Jasper Jig & router. Then I set the driver in place & marked out the bolt holes. Then I drilled the bolt pattern through using a 3/16" drill bit. This is the pilot hole for the Counter Bore Bit. Then I flipped the baffle over and used a 3/4" Counter Bore bit to make the nut recesses. The depth was a guess, I just wanted to be sure I was below the heavy driver relief. Then I cut the rear relief for the driver with a 45 deg chamfer bit.
Lastly I opened up the bolt holes to recommended size of the H-nut and installed nuts.
My guess is your probably after my counter bore tool. ;-x
It’s a little different; it’s actually a metal spot face tool. (McMaster Carr # 3102A28 )
Attached is a pic :T
-David

Cool way to do it... and of course more than one way to accomplish it. I'd guess a 3/4" Forstner bit would work well too, just have to either pre drill or mark well the center for the nut hole.

The counter bore with the pilot rod is pretty slick.

[David_D]

Cool way to do it... and of course more than one way to accomplish it. I'd guess a 3/4" Forstner bit would work well too, just have to either pre drill or mark well the center for the nut hole.

The counter bore with the pilot rod is pretty slick.

Thanks Jon,
The bit was a little pricey but it did just make it real easy. Set the stop on the drill press & go.

-David

[Steve Manning]

Got an idea ...

I saw this thread and wanted to add an idea that I had to get around wood screws and inserts stripping and leaving us with loose speakers. Anyway, I’ve attached a couple of pictures, this is my first shot at using Google SketchUp so things are a little rough and not to scale, but I think you can get the idea. This idea assumes several things, most of us building speakers have access to a router and that most of the baffles we make a made up of several layers. My idea is to get metal bar, (steel or aluminum) ~1/4” thick, ~3/8” wide and cut off 1” long pieces. Drill and tap a hole to accommodate either a 6-32 or 8-32 bolts in the center. In the backside of the front baffle board, router a pocket so that our metal strip sits flush in. Mark and drill a hole through the baffle for the metal insert and bolt to connect. Repeat this for the required number of holes. Then glue the front and back baffle boards together as you normally would. The metal insert can’t fall out and will not spin. I have not tried this yet myself, but intend to give it a try when I do another project. It obviously will take more time than using a wood screw or standard insert, but if you worried about things stripping wood this might solve your problem.

Steve