
Self-tightening nut that provides tight fastening with a unique screw thread - dmmalam
http://akihabaranews.com/2014/10/22/article-en/self-tightening-nut-provides-tight-fastening-aid-unique-screw-thread
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roneesh
I'm a former mechanical engineer specializing in fastening (now I'm a
Javascript developer).

It's certainly interesting that they're managing to keep the tightness up
without resorting to any truly strange designs.

However as some have noted, cost will keep it from being adopted. Let's face
it, fastening is the last thing considered in a project and the last thing
bought. Even for large projects it's at most a few percent of budget and
people are desperate to limit it's cost as much as possible.

Also, truly there's no need for a product like this unless the stress on the
bolt, nut and what's being fastened have to be manage just perfectly.
Otherwise the simplest solution to relaxation is just tightening more. Then it
relaxes to an appropriate stress.

Almost all bolts in the world are under-tightened. Greater analysis of the
joint you're tightening rather than a fancier nut will pay off many more
dividends.

Let me clarify. I applaud the effort, fastening needs research and development
badly, but this is no miracle nut, rather it's a specialized application.

~~~
awkward
As a cyclist who does my own maintenance as a hobby, I am pretty willing to
pay retail-type prices on exotic hardware that requires less effort on my part
and is more reliable on the road.

Not the biggest market, sure, but it's a market where you could very plausibly
sell a single fastener for ten-plus dollars with the right marketing.

~~~
noir_lord
Also a cyclist, biggest issue I have is getting things to the correct torque
as carbon fibre can be a bit of a bugger, I can't recall anything coming lose
on my bike in a long time though.

I doubt I'd buy a 10 dollar but either but if you marketed it as aero I know
some who would ;)

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VLM
If you're bored, try to find anything other than journalist sites reporting on
this. I spent at least five minutes searching and couldn't find anything other
than that. Weird. I was hoping to find the mfgr or a data sheet. My guess,
looking at the one pix available, is the threaded portion acts as a spring. If
you know how a ballscrew works this is kind of a sleeved sprung version of
one. Interesting. Probably a little delicate under high loads. Most likely
I'll continue to use nylocks and/or traditional lockwashers when I build
things, but its and interesting idea.

I wonder how all the patents and trademarks collide vs the "semi-well known"
Hytorc nut, which is basically the same idea but with an integral washer at
the base. Hytorc's are strange little differentially threaded nuts, so instead
of the tension coming from a spring half moon shape, the tension comes from
the secondary fine threading. They're kind of expensive, outta my price
league, so I'm guessing this new nut is going to be out of my league.

~~~
chromaton
You can see the fine level of finish on the completed display units, which
would indicate "expensive" to me as well. Also note that they're going after
machining/manufacturing as the target market rather than, say, automotive,
where cost is king.

~~~
acveilleux
As soon as I saw this, I thought of Aerospace applications. Especially things
like engine mounts, landing gear assemblies, etc. The expensive but few safety
critical fasteners.

~~~
VLM
I saw it the other way, relying on spring pressure isn't wise from a safety
perspective and when it fails parts are going to fall into other parts etc and
torques are pretty high on stuff like that which makes me wonder about torque
limits on this gadget. Also there's no specs on stuff like sideloads or impact
loading or anti-corrosion plating. I'm kinda mystified how this thing could
work if cad plated without scraping off the cad plate, so ...

Where I do see it making an impact, is "every gram counts" and if you took
every washer and lockwasher off an instrument panel and replaced the nuts with
these, you might save a small but measurable mass, which translates directly
into a small but measurable increase in payload or range or lower fuel
consumption or performance. Even on a small plane this might be a pound or
two, but imagine a giant jetliner and it adds up to a respectable mass,
probably financially a good idea... if its ever aerospace rated.

Note that there's kind of big gap between being listed for sale on a foreign
web page with no documentation at all and no specs or datasheets or certs, and
being COTS at a place like "aircraft spruce and specialties". For laughs I
went there and the price to beat for certified aerospace grade locknuts is
like 48 cents a piece, so I donno if this new gadget can compete in the
aerospace market at the typical 100x price markup... I mean sure saving weight
and fuel is cool, but not if each aircraft certified nut costs $500.

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jhallenworld
Is it cheaper than loctite?

A bolt with nut is supposed to work like a kind of high-tension spring pulling
the pieces being fastened together. For large safety critical projects there
is a technology to directly measure the tension of the bolt so that you know
you have tightened the nut enough: [http://www.checkline.com/product/TI-
MINIMAX](http://www.checkline.com/product/TI-MINIMAX)

This is better than a torque spec (where you don't know the friction exactly,
so the bolt tension is an estimate).

~~~
eksith
It may be better than adhesive when repeated removal is necessary. Thread
locking fluid is a pain in smaller applications when the material flakes off
as you untighten, which you have to clean up afterwards. In a clean-room or
other delicate environment, having loose particulates is a big problem.

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cfontes
Would this solve the lose holds problem on climbing gyms?

Where the holds because of the constant pulling and tension unscrew themselves
form the wall and start to rotate, until some unlucky bastard goes for it...

~~~
bronson
Nope! There's no way any climbing gym would rebuild its walls to be full of
expensive proprietary nuts. If they cared, they could use loctite or lock
washers.

It seems there's very little money in fixing spun holds.

~~~
blhack
Climbing gyms change their "routes" pretty frequently, so I don't think they
would use locktite.

~~~
bronson
Why? Loctite Blue is meant to be disassembled and reassembled:
[http://www.loctiteproducts.com/p/t_lkr_blue/overview/Loctite...](http://www.loctiteproducts.com/p/t_lkr_blue/overview/Loctite-
Threadlocker-Blue-242.htm)

Gyms clearly don't use loctite, but I think it's just because the problem
doesn't warrant the slight increase in mess and hassle.

~~~
blhack
Ah, okay. I thought locktite was _only_ a "mostly permanent" adhesive. Thanks
for the info!

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jhallenworld
BTW, this "Eng-Tips Forums" is an excellent resource: [http://www.eng-
tips.com/threadminder.cfm?pid=725](http://www.eng-
tips.com/threadminder.cfm?pid=725)

(fun to read the nuclear engineering forum..)

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kazinator
Those things look ridiculously well-made. Moreover, the thread is not simply
cut in the nut, but rather a threaded insert is joined with the nut casing.
That looks like it is more expensive to make, and could be an Achilles' heel
if it is botched in production. Suppose a manufacturer cuts costs by using a
cheaper metal for the casing, thinking only the threads have to be good
quality; but then the nut is easy to strip. What if the two parts expand at
different rates under heating.

By the way, you can use two nuts to prevent loosening:

[http://en.wikipedia.org/wiki/Nut_%28hardware%29#Use_of_two_n...](http://en.wikipedia.org/wiki/Nut_%28hardware%29#Use_of_two_nuts_to_prevent_self-
loosening)

this could be cheaper than a much more expensive single nut. This article
section explains how vibration causes loosening. The second nut ensures that
the first nut stays in firm contact with the bolt threads even during moments
when the pre-load is momentarily lost due to vibration, and so cannot rotate
loose.

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Scene_Cast2
Saw this on diginfonews a while back, it's a neat concept.

There's one thing that might be problematic with this design. The nut has a
threaded c-shape insert. Due to the threading, when it is in the "wedged"
position, it doesn't just have to close the gap between the tips of the "C"
(let's suppose that this deformation is in the horizontal plane), it also has
to deform vertically due to the threading.

This vertical plus horizontal deformation must be either harsh on the
material, require a relatively small amount of "wedge" (reducing the
usefulness), or have a complex initial shape in anticipation of this type of
deformation.

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bronson
I love the idea of a two part nut that cams itself tight. If weight and
corrosion isn't a problem, this could see some good applications. Maybe
locating on spinning shafts in high heat, or in blind holes?

Stage 8 and safety wire seem simpler and they should offer more predictable
torque for critical applications. Hoping to see some comparisons to existing
solutions and failure analysis.

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JoeAltmaier
Could be huge! Just the increased safety margins could be worth the cost - no
lawsuits when a grinding head dismounts during operation due to loosening nut
or whatever.

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graeham
Or you can just use two regular nuts
[http://en.wikipedia.org/wiki/Jam_nut](http://en.wikipedia.org/wiki/Jam_nut)

~~~
BetaCygni
Yes, but that takes more space and is much harder to fasten correctly. This
actually looks like a good product.

~~~
pp19dd
The RepRap 3D printer I assembled used lots of these (Jam Nuts), and I can
confirm that it was very annoying to keep making geometric adjustments. The
instructions were - assemble loose to keep general structure, then tighten to
exact fit, and then tighten to keep that fit. I ended up buying 4 wrenches to
make my job easier.

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lisper
Is this actually any better than an ordinary nut with a teflon insert?

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ha292
Future YC startup: "XYZ is the self-tightening bolt to self-tightening nuts"

